Adult air pollution exposure and risk of infertility in the Nurses' Health Study II

Windows of susceptibility to air pollution during and surrounding pregnancy in relation to longitudinal maternal measures of adiposity and lipid profiles

Pregnancy is a critical window for long-term metabolic programming of fetal effects stemming from airborne particulate matter ≤2.5 μm (PM2.5) exposure. Yet, little is known about long-term metabolic effects of PM2.5 exposure during and surrounding pregnancy in mothers. We assessed potential critical windows of PM2.5 exposure during and surrounding pregnancy with maternal adiposity and lipid measures later in life. We included 517 pregnant women from the PROGRESS cohort with adiposity [body mass index (BMI), waist circumference (WC), % body fat] and lipids [total cholesterol, high-density-lipoprotein (HDL), low-density-lipoprotein (LDL)] measured repeatedly at 4, 6 and 8 years post-delivery. Monthly average PM2.5 exposure was estimated at each participant's address using a validated spatiotemporal model. We employed distributed lag interaction models (DLIMs) adjusting for socio-demographics and clinical covariates. We found that a 1 μg/m3 increase in PM2.5 exposure throughout mid-/late-pregnancy was associated with higher WC at 6-years post-delivery, peaking at 6 months of gestation: 0.04 cm (95%CI: 0.01, 0.06). We also identified critical windows of PM2.5 exposure during and surrounding pregnancy associated with higher LDL and lower HDL both measured at 4 years post-delivery with peaks at pre-conception for LDL [0.17 mg/dL (95%CI: 0.00, 0.34)] and at the 11th month after conception for HDL [-0.07 mg/dL (95%CI: -0.11, -0.02)]. Stratified analyses by fetal sex indicated stronger associations with adiposity measures in mothers carrying a male, while with lipids in mothers carrying a female fetus. Stratified analyses also indicated potential stronger deleterious lagged effects in women with folic acid intake lower than 600mcg/day during pregnancy.

A retrospective study on the association of ambient air pollutants and temperature co-exposure with female infertility risk in Chengdu, China

Few studies explored air pollution's role in female infertility, especially with temperature factors. Investigating these effects is essential given global climate change and declining fertility rates. This retrospective study, conducted in Chengdu, China, included 1158 patients with primary infertility, 804 patients with secondary infertility, and 1809 fertile women who visited outpatient clinics between 2018 and 2023. Individual exposure levels to six air pollutants and temperatures were determined based on residential addresses. Multinomial logistic regression assessed the associations between air pollutants, temperature, and female infertility across five exposure windows (3-36 months before diagnosis). A stratified analysis by age was performed, and the interactions and combined exposure effects were further evaluated. Exposure to NO2 during 6 and 24 months before diagnosis was associated with a higher risk of primary infertility [OR (95% CI) = 1.17 (1.06-1.28); 1.08 (1.03-1.14)], exposure to PM10 during 24 months before diagnosis was associated with a higher likelihood of primary infertility (OR = 1.32 [1.04-1.57]). Exposure to PM2.5 during the 3 months before diagnosis had a higher risk of secondary infertility (OR = 1.32 [1.08-1.56]), as well as during the 36 months before diagnosis (OR = 1.08 [1.01-1.13]). PM10 exposure during the 3 months, 12, and 36 months before diagnosis (OR = 1.09 [1.01-1.17]; 1.21 [1.05-1.38]; 1.14 [1.03-1.23]), was associated with a higher risk of secondary infertility. Higher temperature exposure in the 3 months before diagnosis was associated with a lower risk of both primary and secondary infertility [OR = 0.92 (0.85-0.96); 0.91 (0.83-0.95)]. Women under 32 years of age exhibited increased sensitivity to NO2, CO, and temperature exposure. Additionally, co-exposure to low temperatures and high concentrations of SO2 or NO2 heightened the risk of primary infertility during the 3 months before diagnosis [OR = 1.86 (1.12-3.04); 1.62 (1.13-2.33)]. Co-exposure to low temperatures and high concentrations of PM10 increased the risk of secondary infertility during 3, 12, and 36 months before diagnosis [OR = 1.51 (1.13-2.03); 1.48 (1.07-2.21); 1.71 (1.13-2.52)]. This study emphasizes the potential for mitigating female infertility risk through reduced exposure to NO2, PM10, and PM2.5, and by appropriately adjusting environmental temperatures.

Environmental pollution and human fertility: investigating the relationship between PM2.5 exposure and assisted reproductive technology outcomes

OBJECTIVE

To investigate the impact of seasonal variations in particulate matter with an aerodynamic diameter of 2.5 µm or less (PM2.5) exposure on assisted reproductive technology (ART) outcomes.

METHODS

This retrospective study, conducted at the First People's Hospital of Shangqiu, analyzed data from 13,476 patients who underwent ART procedures between February 2018 and December 2022. Patients were categorized based on seasonal PM2.5 exposure levels. A generalized additive model (GAM), linear regression analysis, and multivariate logistic regression were used to assess the relationship between PM2.5 exposure and ART outcomes, including oocyte and embryo quality, pregnancy rates, live birth rates, and miscarriage rates.

RESULTS

Significant differences were observed in oocyte number, metaphase II (MII) oocyte number, transferable embryos, and good-quality embryos across seasonal PM2.5 exposure subgroups. Pregnancy rates and live birth rates also demonstrated statistically significant variations. Linear regression analysis revealed a consistent negative correlation between PM2.5 concentrations and key ART outcomes. Multivariate logistic regression analysis, adjusting for age and seasonal variations, confirmed a significant negative association between PM2.5 exposure and both pregnancy rates (OR = 0.995, 95% CI: 0.994-0.996, p < 0.001) and live birth rates (OR = 0.996, 95% CI: 0.995-0.997, p < 0.001). However, no significant relationship was found between PM2.5 exposure and miscarriage rates. GAM analysis further identified a nonlinear, threshold-like association between pregnancy outcomes and predictive factors, with significantly higher live birth rates observed in spring, summer, and autumn compared to winter.

CONCLUSIONS

The study complements existing evidence that exposure to PM2.5 can lead to decreased success rates of pregnancy and live births, as well as significantly impact the outcomes of ART. Future research should focus on developing strategies to mitigate the adverse effects of environmental pollution on ART success rates.

Pregnancy as a Susceptible Period to Ambient Air Pollution Exposure on the Maternal Postpartum Metabolome

Pregnancy is a potential critical window to air pollution exposure for long-term maternal metabolic effects. However, little is known about potential early metabolic mechanisms linking air pollution to maternal metabolic health. We included 544 pregnant Mexican women with both ambient PM2.5 levels during pregnancy and untargeted serum metabolomics to examine associations between pregnancy PM2.5 exposure (overall and monthly) and postpartum metabolites, implementing FDR-adjusted robust linear regression controlling for covariates. Pathway enrichment analyses (in Reactome and MetaboAnalyst) and effect modification by fetal sex and folic acid supplementation were also evaluated. Higher PM2.5 exposure levels throughout pregnancy were associated with higher bile acids and amino acids, dysregulated glycerophospholipids, or lower fatty acyl levels (FDR < 0.05), among other metabolites. Potential critical windows of susceptibility to monthly PM2.5 on metabolites were observed in early to midpregnancy (FDR < 0.005). Main findings were consistent by strata of fetal sex and folic acid supplementation. Metabolic pathways corresponding to positive PM2.5-metabolite associations indicated enriched bile acid, dietary lipid, and transmembrane transport metabolism, whereas for negative PM2.5-metabolite associations, we identified altered pathways involving adipogenesis, incretin peptide hormone, GLP-1, PPAR-alpha, and fatty acid receptors (FDR < 0.05). PM2.5 exposures during pregnancy, especially in early gestation, altered maternal postpartum lipids as well as amino acid metabolism.

Durational Exposure to Particulate Matter and Changes in Fertility Intentions: A Study of Adults in China

OBJECTIVE

The effects of prolonged exposure to persistently elevated atmospheric pollutants, commonly termed air pollution waves, on fertility intentions remain inadequately understood. This study aims to investigate the association between particulate matter (PM) exposure and fertility intentions.

METHODS

In this nationwide cross-sectional study, we analyzed data from 10,747 participants (5496 females and 5251 males). PM waves were defined as periods lasting 3‒6 consecutive days during which the daily average concentrations exceeded China's Ambient Air Quality Standards Grade II thresholds (PM2.5 > 75 μg/m3 and PM10 > 150 μg/m3). We employed multivariate logistic regression models to assess the association between exposure to PM waves and fertility intentions.

RESULTS

Significant inverse associations were detected between exposure to PM2.5 wave events (characterized by concentrations exceeding 75 μg/m3 for durations of 4‒6 days, P < 0.05) and PM10 wave events (defined as concentrations exceeding 150 μg/m3 for 6 consecutive days, P < 0.05) and fertility intentions among females. In contrast, neither the PM2.5 wave nor the PM10 wave events demonstrated statistically significant correlations with fertility intentions in males (P > 0.05 for all comparisons). The potentially susceptible subgroup was identified as females aged 20-30 years.

CONCLUSIONS

Our results provide the first evidence that PM2.5 and PM10 waves are associated with a reduction in female fertility intentions, offering critical insights for the development of public health policies and strategies aimed at individual protection.

Residential Exposure to PM2.5 Constituents and Fecundability in a Danish Preconception Cohort

BACKGROUND

Epidemiologic studies have demonstrated that ambient concentrations of particulate matter < 2.5 μm (PM2.5) are associated with reduced fecundability, the per cycle probability of conception. The specific constituents driving this association are unknown.

OBJECTIVES

We examined the association between ambient concentrations of PM2.5 constituents and fecundability in a Danish preconception cohort study.

METHODS

During 2007-2018, we enrolled female pregnancy planners in an Internet-based preconception cohort study. We included the 5905 participants who had been trying to conceive for < 3 cycles at study enrollment. Participants completed a baseline questionnaire and follow-up questionnaires every 8 weeks to update pregnancy status. We geocoded time-varying residential addresses to estimate ambient concentrations of total PM2.5 and the following PM2.5 constituents: elemental carbon (EC), primary organic aerosol (POA), secondary organic aerosols (SOA), sulfate (SO4 2-), ammonium (NH4 +), nitrate (NO3 -), and sea salt. We averaged concentrations of each pollutant across each menstrual cycle at risk. We fit proportional probabilities regression models to estimate fecundability ratios (FR) and 95% confidence intervals (CI), adjusting for potential confounders and co-pollutants.

RESULTS

Total PM2.5 concentrations were associated with reduced fecundability (the FR for an IQR increase, corresponding to 3.2 μg/m3, was 0.93 [95% CI 0.87, 0.99]). The association was strongest for POA: the FR for an IQR increase, corresponding to 1.3 μg/m3, was 0.92 (95% CI 0.84, 1.01). The corresponding FRs for the remaining PM2.5 constituents were 0.96 (95% CI 0.87, 1.05) for EC (IQR = 0.5 μg/m3), 0.98 (95% CI 0.91, 1.06) for SOA (IQR = 0.5), 0.97 (95% CI 0.92, 1.02) for SO2 4- (IQR = 0.4), 0.95 (95% CI 0.91, 1.01) for NH4 + (IQR = 0.5), 0.97 (95% CI 0.93, 1.01) for NO3 - (IQR = 1.0), and 1.00 (95% CI 0.95, 1.06) for sea salt (IQR = 0.4).

CONCLUSIONS

In this Danish preconception cohort study, PM2.5 constituents derived from biomass and transportation-related combustion may drive the association between PM2.5 concentrations and fecundability.

The unintended consequences of modernity: Pollution and its effect on reproductive, maternal and fetal health

Over the past 50 years there has been an unprecedented increase in pollution globally. Population growth and higher standards of living have resulted in increases in global consumption facilitated by industrialisation and globalisation of goods and services thus resulting in the release of environmental pollutants on a mass scale. This article analyses the effects and consequences of pollution on important aspects of reproductive health including fertility, pregnancy and infant health. It is a narrative review based on a search of PubMed using the terms 'pollution and fertility,' 'pollution and pregnancy,' 'pollution and infant health,' and 'history of pollution.' Additional references were identified through articles provided by the authors of related studies. Studies were included based on their relevance to the topic and were prioritized for their methodological rigour and recency. While no formal quality assessment tools were employed, the potential limitations of individual studies are discussed where applicable.

Particulate air pollution at the time of oocyte retrieval is independently associated with reduced odds of live birth in subsequent frozen embryo transfers

STUDY QUESTION

Does exposure to particulate matter (PM) air pollution prior to oocyte retrieval or subsequent frozen embryo transfer (FET) affect the odds of live birth?

SUMMARY ANSWER

Live birth rates are lower when particulate matter (PM2.5 and PM10) levels are higher prior to oocyte retrieval, regardless of the conditions at the time of embryo transfer.

WHAT IS KNOWN ALREADY

Exposure to air pollution is associated with adverse reproductive outcomes, including reduced fecundity and ovarian reserve, and an increased risk of infertility and pregnancy loss. It is uncertain whether the effect on ART outcomes is due to the effects of pollution on oogenesis or on early pregnancy.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study included 3659 FETs in 1835 patients between January 2013 and December 2021, accounting for all FETs performed at a single clinic over the study period. The primary outcome was the live birth rate per FET. Outcome data were missing for two embryo transfers which were excluded. Daily levels of PM2.5, PM10, nitric oxide, nitrogen dioxide, sulphur dioxide, ozone and carbon monoxide were collected during the study period and calculated for the day of oocyte retrieval and the day of embryo transfer, and during the preceding 2-week, 4-week, and 3-month periods.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Clinical and embryological outcomes were analysed for their association with pollution over 24 hours, 2 weeks, 4 weeks, and 3 months, with adjustment for repeated cycles per participant, age at the time of oocyte retrieval, a quadratic age term, meteorological season, year, and co-exposure to air pollutants. Multi-pollutant models were constructed to adjust for co-exposures to other pollutants. Median concentrations in pollutant quartiles were modelled as continuous variables to test for overall linear trends; a Bonferroni correction was applied to maintain an overall alpha of 0.05 across the four exposure periods tested.

MAIN RESULTS AND THE ROLE OF CHANCE

Increased PM2.5 exposure in the 3 months prior to oocyte retrieval was associated with decreased odds of live birth (linear trend P = 0.011); the odds of live birth when PM2.5 concentrations were in the highest quartile were reduced by 34% (OR 0.66, 95% CI 0.47-0.92) when compared to the lowest quartile. A consistent direction of effect was seen across other exposure periods prior to oocyte retrieval, with an apparent dose-dependent relationship. Increased exposure to PM10 particulate matter in the 2 weeks prior to oocyte retrieval was associated with decreased odds of live birth (linear trend P = 0.009); the odds of live birth were decreased by 38% (OR 0.62, 95% CI 0.43-0.89, P = 0.010) when PM10 concentrations were in the highest quartile compared with the lowest quartile. Consistent trends were not seen across other exposure periods. None of the gaseous pollutants had consistent effects, prior to either oocyte retrieval or embryo transfer.

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective cohort study, however, all FETs during the study period were included and data were missing for only two FETs. The results are based on city-level pollution exposures, and we were not able to adjust for all possible factors that may affect live birth rates. Results were not stratified based on specific patient populations, and it was not possible to calculate the cumulative live birth rate per commenced cycle.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to specifically analyse FETs to separate the effects of environmental exposures prior to oocyte retrieval from those around the time of embryo transfer. Our findings suggest that increased PM exposure prior to oocyte retrieval is associated with reduced live birth rate following FET, independent of the conditions at the time of embryo transfer. Importantly, the air quality during the study period was excellent, suggesting that even 'acceptable' levels of air pollution have detrimental reproductive effects during gametogenesis. At the low pollution levels in our study, exposure to gaseous pollutants did not appear to affect live birth rates. This has important implications for our understanding of the effects of pollution on reproduction, and highlights the urgent need for effective policies limiting pollution exposure to protect human health and reproduction.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was provided for this study. S.J.L. is supported by the Jean Murray Jones Scholarship from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, has received educational sponsorship from Besins, Ferring, Merck, and Organon, honoraria from Hologic and Organon, consulting fees from Merck unrelated to the current study, and is a member of the Reproductive Technology Council of Western Australia. S.J.L. and R.J.H. are board members of Menopause Alliance Australia. C.S.R., M.W., and E.N. have no conflicts of interest to declare. R.J.H. is the Medical Director of Fertility Specialists of Western Australia, the National Medical Director of City Fertility Australia, and a shareholder in CHA SMG. He chairs the Western Australian Minister's Expert Panel on ART and Surrogacy. R.J.H. has made presentations for and received honoraria from Merck, Merck-Serono, Origio, Igenomix, Gideon-Richter, and Ferring, and has received support for attending meetings from Merck, Organon, and Ferring.

TRIAL REGISTRATION NUMBER

N/A.

Beyond the body: Social, structural, and environmental infertility

Infertility is often thought of as a disease of the male or female reproductive system defined by the failure to achieve a pregnancy after 12 months or more of regular, unprotected sexual intercourse. However, as fertility rates rapidly decline worldwide, we observe that the inability to conceive and have children stems not only from anatomical, physiological, or genetic conditions within the body but also from social, structural, and environmental conditions in society. Drawing on a wide array of international and interdisciplinary scholarship, this article rethinks infertility by focusing on the social, structural, and environmental conditions hindering the ability of individuals and couples to have children and become parents. We argue that accounting for infertility requires transcending its biomedical understanding as an individual disease located within the body and address the complex connections between the inability to conceive and the collective and structural dimensions of the environments where people's lives unfold. In doing so, we also emphasise that assisted reproductive technologies are important but not sufficient to tackle the diversity of contemporary infertility experiences. Accomplishing this also requires collective action ranging from family policies improving childcare facilities and parental leave to environmental policies reducing exposure to pollution and toxicity. By rethinking infertility beyond the body, this article contributes new perspectives for understanding the inability to have children, tackling reproductive inequalities, and advancing reproductive justice.

Circulating Interleukin-6 Mediates PM2.5-Induced Ovarian Injury by Suppressing the PPARγ Pathway

Exposure to airborne fine particulate matter (PM2.5) is strongly associated with poor fertility and ovarian damage. However, the mechanism underlying this remains largely unclear. Here, we found that PM2.5 markedly impaired murine ovarian reserve, decreased hormone levels, and aggravated ovarian inflammation. Circulating interleukin-6 (IL-6) was elevated in PM2.5-exposed mice and was further confirmed to mediate this damage by IL-6 recombinant protein intervention. PM2.5 exposure led to increased alveolar macrophage infiltration in the lungs. However, alveolar macrophage clearance with clodronate liposomes could not fully reverse the elevated IL-6 levels and ovarian injury, suggesting that alveolar macrophages were probably not the only source of circulating IL-6. Further experiments indicated that IL-6 mainly targeted ovarian theca-interstitial cells and impaired testosterone synthesis via suppressing the peroxisome proliferator-activated receptor γ (PPARγ) pathway. In addition, apoptosis of granulosa cells and restriction of follicular growth were observed in co-cultures with IL-6-treated theca-interstitial cells, which could be further reversed by the PPARγ agonist. Moreover, IL-6-neutralizing antibodies ameliorated PM2.5-induced ovarian damage. Notably, increased levels of circulating IL-6 were observed in premature ovarian aging patients and were inversely associated with their ovarian function. In summary, our findings offer a mechanistic explanation for PM2.5-induced ovarian dysfunction and verify IL-6 as a biomarker and potential therapeutic target.

How Can Outdoor Air Pollutants Adversely Affect the Women's Fertility? Systematic Review

In the current century, air pollution is known as one of the most critical environmental problems and it is important to find the relations of air pollution and human health. Various air pollutants, such as volatile organic compounds (VOCs), can negatively affect women's fertility. An exhaustive electronic search was done from 2013 until July 2023 in PUBMED and The Cochrane Central Register of Controlled Trials. The following keywords were combined using Boolean hints in the databases queried: air pollution AND (fertility OR miscarriage OR embryo quality OR embryo development OR pregnancy OR implantation OR live birth). The randomized controlled trials, case-control and cohort studies analyzing the impact of air pollutants on fertility were included in the review. In this systematic review, a significant relation was found between the increase in air pollution and the reduction of fertility health, live birth rates, embryo quality, fertility, implantation rates, and miscarriage in exposed women. These results suggest low fertility health rates are associated with traffic-related air pollution. This review has concluded four components (particulate matter, nitrogen dioxide, sulfur, and carbon monoxide) of traffic pollution that can impair women's fertility. Air pollution harms women's fertility. These effects affect gamete's quality at the genetic and epigenetic level. These effects also alter fetal development. Studies have also reported an effect on fetal growth with increased miscarriages. Since air pollution is everywhere and has many sources, it seems necessary to increase the awareness of people and government officials, especially in hygiene and health, to limit air pollutants as much as possible.

Fine particulate matter and ovarian health: A review of emerging risks

Fine particulate matter (PM2.5) pollution has raised significant public concerns, especially for vulnerable populations. Studies have indicated the association between PM2.5 and ovarian disorders, although the mechanisms underlying the effects have not yet been fully elucidated. In this review, we elucidated three main conditions pertaining to ovarian function that may result from exposure to PM2.5: diminished ovarian reserve, polycystic ovary syndrome, and infertility. Specific effects of ovarian disorders caused by PM2.5 are discussed, including reactive oxygen species, apoptosis, DNA damage, and inflammation.

Windows of Susceptibility to Air Pollution During and Surrounding Pregnancy in Relation to Longitudinal Maternal Measures of Adiposity and Lipid Profiles

Pregnancy is a critical window for long-term metabolic programming of fetal effects stemming from airborne particulate matter ≤2.5μm (PM 2.5 ) exposure. Yet, little is known about long-term metabolic effects of PM 2.5 exposure during and surrounding pregnancy in mothers. We assessed potential critical windows of PM 2.5 exposure during and surrounding pregnancy with maternal adiposity and lipid measures later in life. We included 517 pregnant women from the PROGRESS cohort with adiposity [body mass index (BMI), waist circumference (WC), % body fat] and lipids [total cholesterol, high-density-lipoprotein (HDL), low-density-lipoprotein (LDL)] measured repeatedly at 4, 6 and 8 years post-delivery. Monthly average PM 2.5 exposure was estimated at each participant's address using a validated spatiotemporal model. We employed distributed lag interaction models (DLIMs) adjusting for socio-demographics and clinical covariates. We found that a 1 μg/m 3 increase in PM 2.5 exposure throughout mid-/late-pregnancy was associated with higher WC at 6-years post-delivery, peaking at 6 months of gestation: 0.04 cm (95%CI: 0.01, 0.06). We also identified critical windows of PM 2.5 exposure during and surrounding pregnancy associated with higher LDL and lower HDL both measured at 4 years post-delivery with peaks at pre-conception for LDL [0.17 mg/dL (95%CI: 0.00, 0.34)] and at the 11 th month after conception for HDL [-0.07 mg/dL (95%CI: -0.11, -0.02)]. Stratified analyses by fetal sex indicated stronger associations with adiposity measures in mothers carrying a male, whereas stronger associations were observed with lipids in mothers carrying a female fetus. Stratified analyses also indicated potential stronger deleterious lagged effects in women with folic acid intake lower than 600mcg/day during pregnancy.

ATF3 mediates PM2.5-induced apoptosis and inflammation in ovarian granulosa cells

Particulate matter 2.5 (PM2.5) pollution has emerged as a major global public health concern because of its adverse effects on human health. Our group has previously demonstrated that PM2.5 exposure can seriously impair ovarian function. However, the underlying mechanisms remain a mystery. This study verifies ovarian damage in mice, evidenced by inflammatory cell infiltration and follicular atresia, following 5 months of PM2.5 exposure via tracheal drip (35 µg/m³ for low dose and 150 µg/m³ for high dose). In addition, PM2.5 exposure inhibited the cell viability of human granulosa cells (KGN) and induced apoptosis at the concentrations of 50, 100, and 150 µg/mL for 24 h. The apoptosis of KGN cells induced by inflammation contributes to follicular atresia. Furthermore, we conducted RNA-sequencing analysis to identify the genes and pathways triggered by PM2.5 (100 µg/mL) exposure, which decreases the KGN cell viability. We found a significant increase in Activating Transcription Factor 3 (ATF3). Further mechanistic studies reveal a strong association between PM2.5-induced apoptosis, inflammation, and ATF3 with its downstream oxidative stress signals. In summary, the ATF3 pathway serves a vital role in the ovarian injury caused by PM2.5 exposures.

Long term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study

OBJECTIVE

To investigate associations between long term residential exposure to road traffic noise and particulate matter with a diameter <2.5 µm (PM2.5) and infertility in men and women.

DESIGN

Nationwide prospective cohort study.

SETTING

Denmark.

PARTICIPANTS

526 056 men and 377 850 women aged 30-45 years, with fewer than two children, cohabiting or married, and residing in Denmark between 2000 and 2017.

MAIN OUTCOME MEASURE

Incident infertility in men and women during follow-up in the Danish National Patient Register.

RESULTS

Infertility was diagnosed in 16 172 men and 22 672 women during a mean follow-up of 4.3 years and 4.2 years, respectively. Mean exposure to PM2.5 over five years was strongly associated with risk of infertility in men, with hazard ratios of 1.24 (95% confidence interval 1.18 to 1.30) among men aged 30-36.9 years and 1.24 (1.15 to 1.33) among men aged 37-45 years for each interquartile (2.9 µg/m3) higher PM2.5 after adjustment for sociodemographic variables and road traffic noise. PM2.5 was not associated with infertility in women. Road traffic noise (Lden, most exposed facade of residence) was associated with a higher risk of infertility among women aged 35-45 years, with a hazard ratio of 1.14 (1.10 to 1.18) for each interquartile (10.2 dB) higher five year mean exposure. Noise was not associated with infertility among younger women (30-34.9 years). In men, road traffic noise was associated with higher risk of infertility in the 37-45 age group (1.06, 1.02 to 1.11), but not among those aged 30-36.9 years (0.93, 0.91 to 0.96).

CONCLUSIONS

PM2.5 was associated with a higher risk of an infertility diagnosis in men, whereas road traffic noise was associated with a higher risk of an infertility diagnosis in women older than 35 years, and potentially in men older than 37 years. If these results are confirmed in future studies, higher fertility could be added to the list of health benefits from regulating noise and air pollution.

Estimation of couple fecundity in the general population and the association with monthly time-varying ambient particulate matter exposure in low- and middle-income countries: A population-based multi-center epidemiological study

BACKGROUND

Declining total fertility rates have been observed in low- and middle-income countries (LMICs). However, it remains unclear if this trend is related to a reduction in fecundity of general population. Research evidence on contributing factors to fecundity reduction is also limited. We aimed to first estimate couple fecundity in LMICs and then investigate its association with ambient particulate matter (PM) exposure.

METHODS

Using the information from Demographic and Health Surveys between 2003 and 2019, we estimated median time to pregnancy (TTP) and infertility prevalence across 30 LMICs, by employing a current duration approach. Individual PM (PM1, PM2.5, and PM10) exposure during the period of 'at risk' of pregnancy was assessed by months. An accelerated failure model was used to elucidate the association between monthly time-varying PM exposure and TTP. Subsequently, we estimated the prolonged TTP attributable to PM exposures above the World Health Organization (WHO)'s recommended air quality level in 2021.

RESULTS

Within the study regions, median TTP ranged from 6.90 (95 % CI 6.02-7.87) months in Latin America & Caribbean to 10.29 (95 % CI 9.28-11.36) months in East Asia & Pacific, with corresponding infertility prevalence varying from 33 % (95 % CI 29 %-36 %) to 44 % (95 % CI 41 %-48 %). Our estimations indicated that TTP was 1.08 (95 % CI: 0.99-1.18), 1.12 (95 % CI 1.06-1.19), and 1.05 (95 % CI 1.03-1.07) times longer for every 10 μg/m3 increment in PM1, PM2.5, and PM10, respectively. The prolonged TTP attributable to PM exposures surpassing the WHO guideline ranged from 0.11 to 2.81 months across the studied regions.

DISCUSSION

Ambient particulate matter is identified as a potential contributing factor to impaired fecundity in general population of LMICs. The findings underscore the importance of coordinated efforts to control ambient air pollution to mitigate the risk of fecundity reduction among the general population.

Impact of Climate Change on Reproductive Health and Pregnancy Outcomes: A Systematic Review

Climate change has emerged as a significant global health challenge, with growing evidence linking environmental factors to adverse reproductive health outcomes. The primary objective of this review is to assess the effects of climate change-driven environmental factors, such as air pollution and temperature extremes, on reproductive health outcomes, including fertility rates, miscarriage, preterm birth, and congenital anomalies. A comprehensive search of PubMed, Google Scholar, and Web of Science was conducted until July 2024. Studies included in the review were observational, experimental, and randomized controlled trials that reported quantitative data on reproductive outcomes in relation to climate-related environmental exposures. A total of 49 studies were selected for qualitative synthesis. The review found that increased exposure to particulate matter (PM2.5), extreme temperatures, and proximity to traffic were consistently associated with reduced fertility, increased risks of miscarriage, preterm birth, and low birth weight. Adverse effects were particularly pronounced among vulnerable populations, such as pregnant women of lower socioeconomic status and those living in disaster-prone areas. The studies also highlighted potential transgenerational effects, with prenatal exposure to environmental stressors influencing the long-term health of offspring. The findings underscore the urgent need for public health interventions and policies to mitigate environmental exposures that negatively impact reproductive health. Future research should focus on longitudinal and interventional studies to establish causal relationships and inform effective public health strategies.

Mixed effects of ambient air pollutants on oocyte-related outcomes: A novel insight from women undergoing assisted reproductive technology

Air pollution is widely acknowledged as a significant risk factor for human health, especially reproductive health. Nevertheless, many studies have disregarded the potentially mixed effects of air pollutants on reproductive outcomes. We performed a retrospective cohort study involving 8048 women with 9445 cycles undergoing In Vitro Fertilization (IVF) and Intracytoplasmic Sperm Injection (ICSI) in China, from 2017 to 2021. A land-use random forest model was applied to estimate daily residential exposure to air pollutants, including sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and fine particulate matter (PM2.5). Individual and joint associations between air pollutants and oocyte-related outcomes of ART were evaluated. In 90 days prior to oocyte pick-up to oocyte pick-up (period A), NO2, O3 and CO was negatively associated with total oocyte yield. In the 90 days prior to oocyte pick-up to start of gonadotropin medication (Gn start, period B), there was a negative dose-dependent association of exposure to five air pollutants with total oocyte yield and mature oocyte yield. In Qgcomp analysis, increasing the multiple air pollutants mixtures by one quartile was related to reducing the number of oocyte pick-ups by -2.00 % (95 %CI: -2.78 %, -1.22 %) in period A, -2.62 % (95 %CI: -3.40 %, -1.84 %) in period B, and -0.98 % (95 %CI: -1.75 %, -0.21 %) in period C. During period B, a 1-unit increase in the WQS index of multiple air pollutants exposure was associated with fewer number of total oocyte (-1.27 %, 95 %CI: -2.16 %, -0.36 %) and mature oocyte (-1.42 %, 95 %CI: -2.41 %, -0.43 %). O3 and NO2 were major contributors with adverse effects on the mixed associations. Additionally, period B appears to be the susceptible window. Our study implies that exposure to air pollution adversely affects oocyte-related outcomes, which raises concerns about the potential adverse impact of air pollution on women's reproductive health.

Reduced human fecundity attributable to ambient fine particles in low- and middle-income countries

BACKGROUND

Exposure to ambient fine particulate matter (PM2.5) has been associated with reduced human fecundity. However, the attributable burden has not been estimated for low- and middle-income countries (LMICs), where the exposure-response function between PM2.5 and the infertility rate has been insufficiently studied.

OBJECTIVE

This study examined the associations between long-term exposure to PM2.5 and human fecundity indicators, namely the expected time to pregnancy (TTP) and 12-month infertility rate (IR), and then estimated PM2.5-attributable burden of infertility in LMICs.

METHODS

We analyzed 164,593 eligible women from 100 Demographic and Health Surveys conducted in 49 LMICs between 1999 and 2021. We assessed PM2.5 exposures during the 12 months before a pregnancy attempt using the global satellite-derived PM2.5 estimates produced by Atmospheric Composition Analysis Group (ACAG). First, we created a series of pseudo-populations with balanced covariates, given different levels of PM2.5 exposure, using a matching approach based on the generalized propensity score. For each pseudo-population, we used 2-stage generalized Gamma models to derive TTP or IR from the probability distribution of the questionnaire-based duration time for the pregnancy attempt before the interview. Second, we used spline regressions to generate nonlinear PM2.5 exposure-response functions for each of the two fecundity indicators. Finally, we applied the exposure-response functions to estimate number of infertile couples attributable to PM2.5 exposure in 118 LMICs.

RESULTS

Based on the Gamma models, each 10 µg/m3 increment in PM2.5 exposure was associated with a TTP increase by 1.7 % (95 % confidence interval [CI]: -2.3 %-6.0 %) and an IR increase by 2.3 % (95 %CI: 0.6 %-3.9 %). The nonlinear exposure-response function suggested a robust effect of an increased IR for high-concentration PM2.5 exposure (>75 µg/m3). Based on the PM2.5-IR function, across the 118 LMICs, the number of infertile couples attributable to PM2.5 exposure exceeding 35 µg/m3 (the first-stage interim target recommended by the World Health Organization global air quality guidelines) was 0.66 million (95 %CI: 0.061-1.43), accounting for 2.25 % (95 %CI: 0.20 %-4.84 %) of all couples affected by infertility. Among the 0.66 million, 66.5 % were within the top 10 % high-exposure infertile couples, mainly from South Asia, East Asia, and West Africa.

CONCLUSION

PM2.5 contributes significantly to human infertility in places with high levels of air pollution. PM2.5-pollution control is imperative to protect human fecundity in LMICs.

Association between fine particulate matter and fecundability in Henan, China: A prospective cohort study

OBJECTIVE

To investigate the relationship between ambient fine particulate matter (PM2.5) exposure and fecundability.

METHODS

This study included 751,270 female residents from Henan Province who participated in the National Free Pre-conception Check-up Projects during 2015-2017. Ambient cycle-specific PM2.5 exposure was assessed at the county level for each participant using satellite-based PM2.5 concentration data at 1-km resolution. Cox proportional hazards models with time-varying exposure were used to estimate the association between fecundability and PM2.5 exposure, adjusted for potential individual risk factors.

RESULTS

During the study period, 568,713 participants were pregnant, monthly mean PM2.5 concentrations varied from 25.5 to 114.0 µg/m3 across study areas. For each 10 µg/m3 increase in cycle-specific PM2.5, the hazard ratio for fecundability was 0.951 (95 % confidence interval: 0.950-0.953). The association was more pronounced in women who were older, with urban household registration, history of pregnancy, higher body mass index (BMI), hypertension, without exposure to tobacco, or whose male partners were older, with higher BMI, or hypertension.

CONCLUSION

In this population-based prospective cohort, ambient cycle-specific PM2.5 exposure was associated with reduced fecundability. These findings may support the adverse implications of severe air pollution on reproductive health.

The effects of inhaled pollutants on reproduction in marginalized communities: a contemporary review

Important differences in health that are closely linked with social disadvantage exist within and between countries. According to the World Health Organization, life expectancy and good health continue to increase in many parts of the world, but fail to improve in other parts of the world, indicating that differences in life expectancy and health arise due to the circumstances in which people grow, live, work, and age, and the systems put in place to deal with illness. Marginalized communities experience higher rates of certain diseases and more deaths compared to the general population, indicating a profound disparity in health status. Although several factors place marginalized communities at high risk for poor health outcomes, one important factor is exposure to air pollutants. Marginalized communities and minorities are exposed to higher levels of air pollutants than the majority population. Interestingly, a link exists between air pollutant exposure and adverse reproductive outcomes, suggesting that marginalized communities may have increased reproductive disorders due to increased exposure to air pollutants compared to the general population. This review summarizes different studies showing that marginalized communities have higher exposure to air pollutants, the types of air pollutants present in our environment, and the associations between air pollution and adverse reproductive outcomes, focusing on marginalized communities.

Unhealthy air quality secondary to wildfires is associated with lower blastocyst yield

OBJECTIVE

To study the impact of unhealthy air quality from the 2020 Oregon wildfires on outcomes for patients undergoing in vitro fertilization (IVF) treatment.

DESIGN

A retrospective cohort study.

SETTING

A university-based fertility clinic.

PATIENTS

Subjects were undergoing IVF treatment from the 6 weeks preceding the wildfires through a 10-day exposure period. Cohorts were classified on the basis of whether subjects experienced patient and/or laboratory exposure to unhealthy air quality. Patient exposure was defined as at least 4 days of ovarian stimulation overlapping with the exposure, and laboratory exposure was defined as at least 2 days of IVF treatment and embryogenesis overlapping with the exposure. The unexposed cohort consisted of remaining subjects without defined exposure, with cycles in the 6 weeks preceding the wildfires. As some subjects had dual exposure and appeared in both patient and laboratory exposure cohorts, each cohort was separately compared with the unexposed control cohort.

INTERVENTION

A 10-day period of unhealthy air quality caused by smoke plumes from a wildfire event.

MAIN OUTCOME MEASURES

The primary outcome was the blastulation rate. Secondary outcomes included fertilization rate, number of blastocysts obtained, and cycles with no blastocysts frozen or transferred.

RESULTS

Sixty-nine subjects underwent ovarian stimulation and IVF treatment during the 6 weeks preceding the wildfires through the 10-day period of unhealthy air quality. Of these, 15 patients were in the laboratory exposure cohort, 16 were in the patient exposure cohort, and 44 were unexposed. Six subjects appeared in both laboratory and patient exposure cohorts. Although neither exposure cohort had significantly decreased blastulation rate compared with the unexposed, the median number of blastocysts obtained was significantly lower in the laboratory exposure cohort than the unexposed group (2 [range 0-14] vs. 4.5 [range 0-21], respectively). The laboratory exposure cohort had significantly more cycles with no blastocysts obtained (3/15 [20%] vs. 1/44 [2%]). There were no significant differences in IVF treatment outcomes between patient exposure and unexposed cohorts. These findings persisted after controlling for age. There were no significant differences in pregnancy outcomes observed after embryo transfer between the exposure group and the unexposed group.

CONCLUSION

For a cohort of patients undergoing IVF treatment, an acute episode of outside wildfire smoke exposure during fertilization and embryogenesis was associated with decreased blastocyst yield.

Short-Term Nitrogen Dioxide Exposure and Emergency Hospital Admissions for Asthma in Children: A Case-Crossover Analysis in England

Background

There is an increasing body of evidence associating short-term ambient nitrogen dioxide (NO2) exposure with asthma-related hospital admissions in children. However, most studies have relied on temporally resolved exposure information, potentially ignoring the spatial variability of NO2. We aimed to investigate how daily NO2 estimates from a highly resolved spatio-temporal model are associated with the risk of emergency hospital admission for asthma in children in England.

Methods

We conducted a time-stratified case-crossover study including 111,766 emergency hospital admissions for asthma in children (aged 0-14 years) between 1st January 2011 and 31st December 2015 in England. Daily NO2 levels were predicted at the patients' place of residence using spatio-temporal models by combining land use data and chemical transport model estimates. Conditional logistic regression models were used to obtain the odds ratios (OR) and confidence intervals (CI) after adjusting for temperature, relative humidity, bank holidays, and influenza rates. The effect modifications by age, sex, season, area-level income deprivation, and region were explored in stratified analyses.

Results

For each 10 µg/m³ increase in NO2 exposure, we observed an 8% increase in asthma-related emergency admissions using a five-day moving NO2 average (mean lag 0-4) (OR 1.08, 95% CI 1.06-1.10). In the stratified analysis, we found larger effect sizes for male (OR 1.10, 95% CI 1.07-1.12) and during the cold season (OR 1.10, 95% CI 1.08-1.12). The effect estimates varied slightly by age group, area-level income deprivation, and region.

Significance

Short-term exposure to NO2 was significantly associated with an increased risk of asthma emergency admissions among children in England. Future guidance and policies need to consider reflecting certain proven modifications, such as using season-specific countermeasures for air pollution control, to protect the at-risk population.

Research progress on mitochondrial damage and repairing in oocytes: A review

Oocytes are the female germ cells, which are susceptible to stress stimuli. The development of oocytes in the ovary is affected by many environmental and metabolic factors, food toxins, aging, and pathological factors. Mitochondria are the main target organelles of these factors, and the damage to mitochondrial structure and function can affect the production of ATP, the regulation of redox reactions, and apoptosis in oocytes. Mitochondrial damage is closely related to the decrease in oocyte quality and is the main factor leading to female infertility. Antioxidant foods or drugs have been used to prevent mitochondrial damage from some stressors or to repair damaged mitochondria, thereby improving oocyte development and female reproductive outcomes. In this paper, the damage of mitochondria during oocyte development by the above factors has been reviewed, and the relevant measures to alleviate the damage of mitochondria in oocytes have been discussed. Our findings may provide a theoretical basis and experimental basis for improving female fertility.

Ambient traffic related air pollution in relation to ovarian reserve and oocyte quality in young, healthy oocyte donors

Studies in mice and older, subfertile women have found that air pollution exposure may compromise female reproduction. Our objective was to evaluate the effects of air pollution on ovarian reserve and outcomes of ovarian stimulation among young, healthy females. We included 472 oocyte donors who underwent 781 ovarian stimulation cycles at a fertility clinic in Atlanta, Georgia, USA (2008-2019). Antral follicle count (AFC) was assessed with transvaginal ultrasonography and total and mature oocyte count was assessed following oocyte retrieval. Ovarian sensitivity index (OSI) was calculated as the total number of oocytes divided by total gonadotrophin dose × 1000. Daily ambient exposure to nitric oxide (NOx), carbon monoxide (CO), and particulate matter ≤ 2.5 (PM2.5) was estimated using a fused regional + line-source model for near-surface releases at a 250 m resolution based on residential address. Generalized estimating equations were used to evaluate the associations of an interquartile range (IQR) increase in pollutant exposure with outcomes adjusted for donor characteristics, census-level poverty, and meteorological factors. The median (IQR) age among oocyte donors was 25.0 (5.0) years, and 31% of the donors were racial/ethnic minorities. The median (IQR) exposure to NOx, CO, and PM2.5 in the 3 months prior to stimulation was 37.7 (32.0) ppb, 612 (317) ppb, and 9.8 (2.9) µg/m3, respectively. Ambient air pollution exposure in the 3 months before AFC was not associated with AFC. An IQR increase in PM2.5 in the 3 months before AFC and during stimulation was associated with -7.5% (95% CI -14.1, -0.4) and -6.4% (95% CI -11.0, -1.6) fewer mature oocytes, and a -1.9 (95% CI -3.2, -0.5) and -1.0 (95% CI -1.8, -0.2) lower OSI, respectively. Our results suggest that lowering the current 24-h PM2.5 standard in the US to 25 µg/m3 may still not adequately protect against the reprotoxic effects of short-term PM2.5 exposure.

Air pollution and pregnancy

Increased fossil fuel usage and extreme climate change events have led to global increases in greenhouse gases and particulate matter with 99% of the world's population now breathing polluted air that exceeds the World Health Organization's recommended limits. Pregnant women and neonates with exposure to high levels of air pollutants are at increased risk of adverse health outcomes such as maternal hypertensive disorders, postpartum depression, placental abruption, low birth weight, preterm birth, infant mortality, and adverse lung and respiratory effects. While the exact mechanism by which air pollution exerts adverse health effects is unknown, oxidative stress as well as epigenetic and immune mechanisms are thought to play roles. Comprehensive, global efforts are urgently required to tackle the health challenges posed by air pollution through policies and action for reducing air pollution as well as finding ways to protect the health of vulnerable populations in the face of increasing air pollution.

Air pollution and fecundability in a North American preconception cohort study

BACKGROUND

Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. However, the level of evidence is limited and specific pollutants driving the association are inconsistent across studies.

METHODS

We used data from a web-based preconception cohort study of pregnancy planners enrolled during 2013-2019 (Pregnancy Study Online; PRESTO). Eligible participants self-identified as female, were aged 21-45 years, resided in the United States (U.S.) or Canada, and were trying to conceive without fertility treatments. Participants completed a baseline questionnaire and bi-monthly follow-up questionnaires until conception or 12 months. We analyzed data from 8,747 participants (U.S.: 7,304; Canada: 1,443) who had been trying to conceive for < 12 cycles at enrollment. We estimated residential ambient concentrations of particulate matter < 2.5 µm (PM2.5), nitrogen dioxide (NO2), and ozone (O3) using validated spatiotemporal models specific to each country. We fit country-specific proportional probabilities regression models to estimate the association between annual average, menstrual cycle-specific, and preconception average pollutant concentrations with fecundability, the per-cycle probability of conception. We calculated fecundability ratios (FRs) and 95% confidence intervals (CIs) and adjusted for individual- and neighborhood-level confounders.

RESULTS

In the U.S., the FRs for a 5-µg/m3 increase in annual average, cycle-specific, and preconception average PM2.5 concentrations were 0.94 (95% CI: 0.83, 1.08), 1.00 (95% CI: 0.93, 1.07), and 1.00 (95% CI: 0.93, 1.09), respectively. In Canada, the corresponding FRs were 0.92 (95% CI: 0.74, 1.16), 0.97 (95% CI: 0.87, 1.09), and 0.94 (95% CI: 0.80, 1.09), respectively. Likewise, NO2 and O3 concentrations were not strongly associated with fecundability in either country.

CONCLUSIONS

Neither annual average, menstrual cycle-specific, nor preconception average exposure to ambient PM2.5, NO2, and O3 were appreciably associated with reduced fecundability in this cohort of pregnancy planners.

Elucidating disease-associated mechanisms triggered by pollutants via the epigenetic landscape using large-scale ChIP-Seq data

BACKGROUND

Despite well-documented effects on human health, the action modes of environmental pollutants are incompletely understood. Although transcriptome-based approaches are widely used to predict associations between chemicals and disorders, the molecular cues regulating pollutant-derived gene expression changes remain unclear. Therefore, we developed a data-mining approach, termed "DAR-ChIPEA," to identify transcription factors (TFs) playing pivotal roles in the action modes of pollutants.

METHODS

Large-scale public ChIP-Seq data (human, n = 15,155; mouse, n = 13,156) were used to predict TFs that are enriched in the pollutant-induced differentially accessible genomic regions (DARs) obtained from epigenome analyses (ATAC-Seq). The resultant pollutant-TF matrices were then cross-referenced to a repository of TF-disorder associations to account for pollutant modes of action. We subsequently evaluated the performance of the proposed method using a chemical perturbation data set to compare the outputs of the DAR-ChIPEA and our previously developed differentially expressed gene (DEG)-ChIPEA methods using pollutant-induced DEGs as input. We then adopted the proposed method to predict disease-associated mechanisms triggered by pollutants.

RESULTS

The proposed approach outperformed other methods using the area under the receiver operating characteristic curve score. The mean score of the proposed DAR-ChIPEA was significantly higher than that of our previously described DEG-ChIPEA (0.7287 vs. 0.7060; Q = 5.278 × 10-42; two-tailed Wilcoxon rank-sum test). The proposed approach further predicted TF-driven modes of action upon pollutant exposure, indicating that (1) TFs regulating Th1/2 cell homeostasis are integral in the pathophysiology of tributyltin-induced allergic disorders; (2) fine particulates (PM2.5) inhibit the binding of C/EBPs, Rela, and Spi1 to the genome, thereby perturbing normal blood cell differentiation and leading to immune dysfunction; and (3) lead induces fatty liver by disrupting the normal regulation of lipid metabolism by altering hepatic circadian rhythms.

CONCLUSIONS

Highlighting genome-wide chromatin change upon pollutant exposure to elucidate the epigenetic landscape of pollutant responses outperformed our previously described method that focuses on gene-adjacent domains only. Our approach has the potential to reveal pivotal TFs that mediate deleterious effects of pollutants, thereby facilitating the development of strategies to mitigate damage from environmental pollution.

Toxicity of microplastics and nanoplastics: invisible killers of female fertility and offspring health

Microplastics (MPs) and nanoplastics (NPs) are emergent pollutants, which have sparked widespread concern. They can infiltrate the body via ingestion, inhalation, and cutaneous contact. As such, there is a general worry that MPs/NPs may have an impact on human health in addition to the environmental issues they engender. The threat of MPs/NPs to the liver, gastrointestinal system, and inflammatory levels have been thoroughly documented in the previous research. With the detection of MPs/NPs in fetal compartment and the prevalence of infertility, an increasing number of studies have put an emphasis on their reproductive toxicity in female. Moreover, MPs/NPs have the potential to interact with other contaminants, thus enhancing or diminishing the combined toxicity. This review summarizes the deleterious effects of MPs/NPs and co-exposure with other pollutants on female throughout the reproduction period of various species, spanning from reproductive failure to cross-generational developmental disorders in progenies. Although these impacts may not be directly extrapolated to humans, they do provide a framework for evaluating the potential mechanisms underlying the reproductive toxicity of MPs/NPs.

Association between traffic-related air pollution exposure and fertility-assisted births

Previous studies have suggested that traffic-related air pollution is associated with adverse fertility outcomes, such as reduced fecundability and subfertility. The purpose of this research is to investigate if PM_2.5 exposure prior to conception or traffic-related exposures (traffic density and distance to nearest major roadway) at birth address is associated with fertility-assisted births. We obtained all live and still births from the Massachusetts state birth registry with an estimated conception date between January 2002 through December 2008. All births requiring fertility drugs or assisted reproductive technology were identified as cases. We randomly selected 2000 infants conceived each year to serve as a common control group. PM_2.5 exposure was assessed using 4 km spatial satellite remote sensing, meteorological and land use spatiotemporal models at geocoded birth addresses for the year prior to conception. The mean PM_2.5 level was 9.81 µg m^-3 (standard deviation = 1.70 µg m^-3), with a maximum of 14.27 µg m^-3. We calculated crude and adjusted fertility treatment odds ratios (ORs) and 95% confidence intervals (CI) per interquartile range of 1.72 µg m^-3 increase in PM_2.5 exposure. Our final analyses included 10 748 fertility-assisted births and 12 225 controls. After adjusting for parental age, marital status, race, maternal education, insurance status, parity, and year of birth, average PM_2.5 exposure during the year prior to conception was weakly associated with fertility treatment (OR: 1.01; 95% CI: 0.97, 1.05). Fertility-assisted births were inversely associated with traffic density (highest quartile compared to lowest quartile, OR: 0.92; 95% CI: 0.83, 1.02) and positively associated with distance from major roadway (OR per 100 m: 1.01; 95% CI: 1.00, 1.02) in adjusted analyses. We did not find strong evidence to support an adverse relationship between traffic-related air pollution exposure and fertility-assisted births.

Environmental and occupational factors and higher risk of couple infertility: a systematic review study

Background

Infertility is a global health problem that represents an increasing trend due to new lifestyles following technological advances since individuals are facing more risk factors than before. The present systematic review study aimed to investigate the impact of environmental and occupational factors on reproductive parameters and increased risk of couple infertility.

Main body

Scopus, PubMed, SID, and Web of Science databases were searched for the available observational (i.e., cohort, case-control, and cross-sectional) systematic review, meta-analysis, and clinical trial studies between 2007 and 2019. To this end, keywords such as ‘Environmental exposure’, ‘Occupational exposure’, ‘Environmental pollutants’, ‘Environmental pollution’, ‘Couple infertility’, ‘Sterility’, and ‘Sub-fertility’ were used. The retrieved investigations examined the impact of environmental and occupational risk factors on reproductive indices and increased infertility risk. Totally, 66 out of 9519 papers were evaluated after considering the inclusion and exclusion criteria. The reported risk factors in the reviewed studies were heavy metals, cigarette smoking, and exposure to chemicals through consumer goods, urban life, and proximity to main roads. In addition, occupational factors included heavy physical activity, prolonged sitting, exposure to a hot environment, contact with formaldehyde, pesticides, insecticides, mechanical vibration, and contact with ionizing radiation, all of which affected the reproductive parameters. However, some researchers found no significant associations in this regard.

Short conclusion

In general, individuals with known impairments in reproductive parameters were more exposed to risk factors. Nonetheless, more studies are needed to determine the risk of infertility in the population.

Airway pollution and smoking in reproductive health

Environmental exposure refers to contact with chemical, biological, or physical substances found in air, water, food, or soil that may have a harmful effect on a person's health. Almost all of the global population (99%) breathe air that contains high levels of pollutants. Smoking is one of the most common forms of recreational drug use and is the leading preventable cause of morbidity and mortality worldwide. The small particles from either ambient (outdoor) pollution or cigarette smoke are inhaled to the lungs and quickly absorbed into the bloodstream. These substances can affect virtually every organ in our body and have been associated with various respiratory, cardiovascular, endocrine, and also reproductive morbidities, including decreased fertility, adverse pregnancy outcomes, and offspring long-term morbidity. This review summarizes the latest literature reporting the reproductive consequences of women exposed to ambient (outdoor) air pollution and cigarette smoking.

Using follicular fluid metabolomics to investigate the association between air pollution and oocyte quality

BACKGROUND AND AIM

Our objective was to use metabolomics in a toxicological-relevant target tissue to gain insight into the biological processes that may underlie the negative association between air pollution exposure and oocyte quality.

METHODS

Our study included 125 women undergoing in vitro fertilization at an academic fertility center in Massachusetts, US (2005-2015). A follicular fluid sample was collected during oocyte retrieval and untargeted metabolic profiling was conducted using liquid chromatography with ultra-high-resolution mass spectrometry and two chromatography columns (C18 and HILIC). Daily exposure to nitrogen dioxide (NO2), ozone, fine particulate matter, and black carbon was estimated at the women's residence using spatiotemporal models and averaged over the period of ovarian stimulation (2-weeks). Multivariable linear regression models were used to evaluate the associations between the air pollutants, number of mature oocytes, and metabolic feature intensities. A meet-in-the-middle approach was used to identify overlapping features and metabolic pathways.

RESULTS

Of the air pollutants, NO2 exposure had the largest number of overlapping metabolites (C18: 105; HILIC: 91) and biological pathways (C18: 3; HILIC: 6) with number of mature oocytes. Key pathways of overlap included vitamin D3 metabolism (both columns), bile acid biosynthesis (both columns), C21-steroid hormone metabolism (HILIC), androgen and estrogen metabolism (HILIC), vitamin A metabolism (HILIC), carnitine shuttle (HILIC), and prostaglandin formation (C18). Three overlapping metabolites were confirmed with level-1 or level-2 evidence. For example, hypoxanthine, a metabolite that protects against oxidant-induced cell injury, was positively associated with NO2 exposure and negatively associated with number of mature oocytes. Minimal overlap was observed between the other pollutants and the number of mature oocytes.

CONCLUSIONS

Higher exposure to NO2 during ovarian stimulation was associated with many metabolites and biologic pathways involved in endogenous vitamin metabolism, hormone synthesis, and oxidative stress that may mediate the observed associations with lower oocyte quality.

Effects of Exposure Duration and Exposure Levels of Ambient Air Pollutants on the Risk of Polycystic Ovarian Syndrome: A 2015-2019 Korean Population-Based Cohort Study

Exposure to ambient air pollution is associated with an increased risk of menstrual disorders and infertility. This study examined the relationships between the levels and duration of air pollution exposure and the risk of polycystic ovarian syndrome (PCOS) using Korean population-based cohort data (2015-2019). Real-time data on PM₁₀, PM_2.5, O₃, CO, SO₂, and NO₂ were provided by the Korean Ministry of Environment. The average monthly air pollutant concentration from 1 January 2014 to 31 December 2018 was analyzed. To assess individual-level exposure to air pollutants, a spatial prediction model and an area-averaging approach were used. In total, 237,582 PCOS cases were analyzed. The annual age-adjusted PCOS incidence was 6.70, 8.28, 9.73, 11.58, and 11.97% from 2015-2019, respectively. The PCOS risk increased 1.29-1.32, 1.43-1.52, and 1.32-fold following exposure to the 2-year and 3-year average levels of PM_2.5, O₃, and NO₂, respectively, compared to their 1-year average levels. The PCOS risk increased 1.75-fold (95% confidence interval: 1.66-1.85) in the fourth-quartile for the NO₂ level. Increased SO₂ and CO levels in the second- and third-quartiles were also associated with an increased PCOS risk. Exposure to air pollutants thus increased the risk for PCOS in the Korean population.

Systematic review of climate change effects on reproductive health

Climate change is a major risk factor for overall health, including reproductive health, and well-being. Increasing temperatures, due mostly to increased greenhouse gases trapping excess heat in the atmosphere, result in erratic weather patterns, wildfires, displacement of large communities, and stagnant water resulting in vector-borne diseases that, together, have set the stage for new and devastating health threats across the globe. These conditions disproportionately affect disadvantaged and vulnerable populations, including women, pregnant persons, young children, the elderly, and the disabled. This review reports on the evidence for the adverse impacts of air pollution, wildfires, heat stress, floods, toxic chemicals, and vector-borne diseases on male and female fertility, the developing fetus, and obstetric outcomes. Reproductive health care providers are uniquely positioned and have an unprecedented opportunity to educate patients and policy makers about mitigating the impact of climate change to assure reproductive health in this and future generations.

Ambient Air Pollution Exposure Assessments in Fertility Studies: a Systematic Review and Guide for Reproductive Epidemiologists

Purpose of Review

We reviewed the exposure assessments of ambient air pollution used in studies of fertility, fecundability, and pregnancy loss.

Recent Findings

Comprehensive literature searches were performed in the PUBMED, Web of Science, and Scopus databases. Of 168 total studies, 45 met the eligibility criteria and were included in the review. We find that 69% of fertility and pregnancy loss studies have used one-dimensional proximity models or surface monitor data, while only 35% have used the improved models, such as land-use regression models (4%), dispersion/chemical transport models (11%), or fusion models (20%). No published studies have used personal air monitors.

Summary

While air pollution exposure models have vastly improved over the past decade from a simple, one-dimensional distance or air monitor data to models that incorporate physiochemical properties leading to better predictive accuracy, precision, and increased spatiotemporal variability and resolution, the fertility literature has yet to fully incorporate these new methods. We provide descriptions of each of these air pollution exposure models and assess the strengths and limitations of each model, while summarizing the findings of the literature on ambient air pollution and fertility that apply each method.

Influence of ambient air pollution on successful pregnancy with frozen embryo transfer: A machine learning prediction model

Numerous air pollutants have been reported to influence the outcomes of in vitro fertilization (IVF). However, whether air pollution affects implantation in frozen embryo transfer (FET) process is under debate. We aimed to find the association between ambient air pollution and implantation potential of FET and test the value of adding air pollution data to a random forest model (RFM) predicting intrauterine pregnancy. Using a retrospective study of a 4-year single-center design，we analyzed 3698 cycles of women living in Shanghai who underwent FET between 2015 and 2018. To estimate patients' individual exposure to air pollution, we computed averages of daily concentrations of six air pollutants including PM_2.5, PM₁₀, SO₂, CO, NO₂, and O₃ measured at 9 monitoring stations in Shanghai for the exposure period (one month before FET). Moreover, A predictive model of 15 variables was established using RFM. Air pollutants levels of patients with or without intrauterine pregnancy were compared. Our results indicated that for exposure periods before FET, NO₂ were negatively associated with intrauterine pregnancy (OR: 0.906, CI: 0.816-0.989). AUROC increased from 0.712 to 0.771 as air pollutants features were added. Overall, our findings demonstrate that exposure to NO₂ before transfer has an adverse effect on clinical pregnancy. The performance to predict intrauterine pregnancy will improve with the use of air pollution data in RFM.

Fine particulate matter and polycystic ovarian morphology

BACKGROUND

Polycystic ovary morphology (PCOM) is an ultrasonographic finding that can be present in women with ovulatory disorder and oligomenorrhea due to hypothalamic, pituitary, and ovarian dysfunction. While air pollution has emerged as a possible disrupter of hormone homeostasis, limited research has been conducted on the association between air pollution and PCOM.

METHODS

We conducted a longitudinal cohort study using electronic medical records data of 5,492 women with normal ovaries at the first ultrasound that underwent a repeated pelvic ultrasound examination during the study period (2004-2016) at Boston Medical Center. Machine learning text algorithms classified PCOM by ultrasound. We used geocoded home address to determine the ambient annual average PM2.5 exposures and categorized into tertiles of exposure. We used Cox Proportional Hazards models on complete data (n = 3,994), adjusting for covariates, and additionally stratified by race/ethnicity and body mass index (BMI).

RESULTS

Cumulative exposure to PM2.5 during the study ranged from 4.9 to 17.5 µg/m3 (mean = 10.0 μg/m3). On average, women were 31 years old and 58% were Black/African American. Hazard ratios and 95% confidence intervals (CI) comparing the second and third PM2.5 exposure tertile vs. the reference tertile were 1.12 (0.88, 1.43) and 0.89 (0.62, 1.28), respectively. No appreciable differences were observed across race/ethnicity. Among women with BMI ≥ 30 kg/m2, we observed weak inverse associations with PCOM for the second (HR: 0.93, 95% CI: 0.66, 1.33) and third tertiles (HR: 0.89, 95% CI: 0.50, 1.57).

CONCLUSIONS

In this study of reproductive-aged women, we observed little association between PM2.5 concentrations and PCOM incidence. No dose response relationships were observed nor were estimates appreciably different across race/ethnicity within this clinically sourced cohort.

Concentrated ambient fine particles exposure affects ovarian follicle development in mice

BACKGROUND

Ambient fine particles (PM_2.5) are known to cause various reproductive and developmental diseases. However, the potential mechanisms of PM_2.5 exposure induced female reproductive damage remain unclear.

METHODS

Four weeks old female C57BL/6 J mice were exposed to filtered air (FA, n = 10) or concentrated ambient PM_2.5 (CAP, n = 10) using a versatile aerosol concentration enrichment system. After 9 weeks of the exposure, mice were sacrificed under sevoflurane anesthesia and tissue samples were collected. Immunohistochemical analysis, enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, and RNA-sequencing were performed to analyze the effects of PM_2.5 exposure on follicle development and elucidate its potential mechanisms.

RESULTS

Chronic PM_2.5 exposure resulted in follicular dysplasia. Compared to the FA-exposed group, follicular atresia in the CAP-exposed mice were significantly increased. Further studies confirmed that CAP induced apoptosis in granulosa cells, accompanied by a distortion of hormone homeostasis. In addition, RNA-sequencing data demonstrated that CAP exposure induced the alteration of ovarian gene expressions and was associated with inflammatory response.

CONCLUSIONS

Chronic exposure to CAP can induce follicular atresia, which was associated with hormone modulation and inflammation.

Exposure to environmentally relevant concentrations of ambient fine particulate matter (PM2.5) depletes the ovarian follicle reserve and causes sex-dependent cardiovascular changes in apolipoprotein E null mice

BACKGROUND

Fine particulate matter (PM_2.5) exposure accelerates atherosclerosis and contains known ovotoxic chemicals. However, effects of exposure to PM_2.5 on the finite ovarian follicle pool have hardly been investigated, nor have interactions between ovarian and cardiovascular effects. We hypothesized that subchronic inhalation exposure to human-relevant concentrations of PM_2.5 results in destruction of ovarian follicles via apoptosis induction, as well as accelerated recruitment of primordial follicles into the growing pool. Further, we hypothesized that destruction of ovarian follicles enhances the adverse cardiovascular effects of PM_2.5 in females.

RESULTS

Hyperlipidemic apolipoprotein E (Apoe) null ovary-intact or ovariectomized female mice and testis-intact male mice were exposed to concentrated ambient PM_2.5 or filtered air for 12 weeks, 5 days/week for 4 h/day using a versatile aerosol concentration enrichment system. Primordial, primary, and secondary ovarian follicle numbers were decreased by 45%, 40%, and 17%, respectively, in PM_2.5-exposed ovary-intact mice compared to controls (P < 0.05). The percentage of primary follicles with granulosa cells positive for the mitosis marker Ki67 was increased in the ovaries from PM_2.5-exposed females versus controls (P < 0.05), consistent with increased recruitment of primordial follicles into the growing pool. Exposure to PM_2.5 increased the percentages of primary and secondary follicles with DNA damage, assessed by γH2AX immunostaining (P < 0.05). Exposure to PM_2.5 increased the percentages of apoptotic antral follicles, determined by TUNEL and activated caspase 3 immunostaining (P < 0.05). Removal of the ovaries and PM_2.5-exposure exacerbated the atherosclerotic effects of hyperlipidemia in females (P < 0.05). While there were statistically significant changes in blood pressure and heart rate variability in PM_2.5-compared to Air-exposed gonad-intact males and females and ovariectomized females, the changes were not consistent between exposure years and assessment methods.

CONCLUSIONS

These results demonstrate that subchronic PM_2.5 exposure depletes the ovarian reserve by increasing recruitment of primordial follicles into the growing pool and increasing apoptosis of growing follicles. Further, PM_2.5 exposure and removal of the ovaries each increase atherosclerosis progression in Apoe-/- females. Premature loss of ovarian function is associated with increased risk of osteoporosis, cardiovascular disease and Alzheimer's disease in women. Our results thus support possible links between PM_2.5 exposure and other adverse health outcomes in women.

Air pollution and fecundability: Results from a Danish preconception cohort study

BACKGROUND

Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. Epidemiologic studies have been restricted largely to couples undergoing fertility treatment or have retrospectively ascertained time-to-pregnancy among pregnant women.

OBJECTIVES

We examined the association between residential ambient air pollution and fecundability, the per-cycle probability of conception, in a large preconception cohort of Danish pregnancy planners.

METHODS

During 2007-2018, we used the Internet to recruit and follow women who were trying to conceive without the use of fertility treatment. Participants completed an online baseline questionnaire eliciting socio-demographic characteristics, lifestyle factors, and medical and reproductive histories and follow-up questionnaires every 8 weeks to ascertain pregnancy status. We determined concentrations of ambient nitrogen oxides (NOx ), nitrogen dioxide (NO2 ), carbon monoxide (CO), ozone (O3 ), particulate matter <2.5 µm (PM2.5 ) and <10 µm (PM10 ), and sulphur dioxide (SO2 ) at each participant's residential address. We calculated average exposure during the year before baseline, during each menstrual cycle over follow-up and during the entire pregnancy attempt time. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for potential confounders and co-pollutants. The analysis was restricted to the 10,183 participants who were trying to conceive for <12 cycles at study entry whose addresses could be geocoded.

RESULTS

During 12 months of follow-up, 73% of participants conceived. Higher concentrations of PM2.5 and PM10 were associated with small reductions in fecundability. For example, the FRs for a one interquartile range (IQR) increase in PM2.5 (IQR = 3.2 µg/m3 ) and PM10 (IQR = 5.3 µg/m3 ) during each menstrual cycle were 0.93 (95% CI: 0.87, 0.99) and 0.91 (95% CI: 0.84, 0.99), respectively. Other air pollutants were not appreciably associated with fecundability.

CONCLUSIONS

In this preconception cohort study of Danish women, residential exposures to PM2.5 and PM10 were associated with reduced fecundability.

The impact of fine particulate matter (PM) on various beneficial functions of human endometrial stem cells through its key regulator SERPINB2

Fine particulate matter (PM) has a small diameter but a large surface area; thus, it may have broad toxic effects that subsequently damage many tissues of the human body. Interestingly, many studies have suggested that the recent decline in female fertility could be associated with increased PM exposure. However, the precise mechanisms underlying the negative effects of PM exposure on female fertility are still a matter of debate. A previous study demonstrated that resident stem cell deficiency limits the cyclic regenerative capacity of the endometrium and subsequently increases the pregnancy failure rate. Therefore, we hypothesized that PM exposure induces endometrial tissue damage and subsequently reduces the pregnancy rate by inhibiting various beneficial functions of local endometrial stem cells. Consistent with our hypothesis, we showed for the first time that PM exposure significantly inhibits various beneficial functions of endometrial stem cells, such as their self-renewal, transdifferentiation, and migratory capacities, in vitro and in vivo through the PM target gene SERPINB2, which has recently been shown to be involved in multiple stem cell functions. In addition, the PM-induced inhibitory effects on the beneficial functions of endometrial stem cells were significantly diminished by SERPINB2 depletion. Our findings may facilitate the development of promising therapeutic strategies for improving reproductive outcomes in infertile women.

Airborne pollutants may reduce female fertility through their debilitating effects on the stem cells that maintain the endometrium, the interior lining of the uterus. Recent evidence suggests that toxic byproducts from fossil fuels known as ‘particulate matter’ represent a danger to women’s reproductive health. South Korean researchers led by Ji-Won Jung, Korea Centers for Disease Control and Prevention, and In-Sun Hong, Gachon University, Incheon, have investigated this risk by exposing cultured human endometrial stem cells to diesel-derived particulate matter. These stem cells normally maintain the endometrium, allowing embryonic implantation to take place, but exposure to particulate matter greatly impaired the cells’ regenerative function. Mice exposed to particulate matter exhibited similar impairments of endometrial maintenance. The researchers identified a molecular pathway associated with this response that could guide development of fertility-restoring treatments.

Climate change, women's health, and the role of obstetricians and gynecologists in leadership

Climate change is one of the major global health threats to the world's population. It is brought on by global warming due in large part to increasing levels of greenhouse gases resulting from human activity, including burning fossil fuels (carbon dioxide), animal husbandry (methane from manure), industry emissions (ozone, nitrogen oxides, sulfur dioxide), vehicle/factory exhaust, and chlorofluorocarbon aerosols that trap extra heat in the earth's atmosphere. Resulting extremes of weather give rise to wildfires, air pollution, changes in ecology, and floods. These in turn result in displacement of populations, family disruption, violence, and major impacts on water quality and availability, food security, public health and economic infrastructures, and limited abilities for civil society to maintain citizen safety. Climate change also has direct impacts on human health and well-being. Particularly vulnerable populations are affected, including women, pregnant women, children, the disabled, and the elderly, who comprise the majority of the poor globally. Additionally, the effects of climate change disproportionally affect disadvantaged communities, including low income and communities of color, and lower-income countries that are at highest risk of adverse impacts when disasters occur due to inequitable distribution of resources and their socioeconomic status. The climate crisis is tilting the risk balance unfavorably for women's sexual and reproductive health and rights as well as newborn and child health. Obstetrician/gynecologists have the unique opportunity to raise awareness, educate, and advocate for mitigation strategies to reverse climate change affecting our patients and their families. This article puts climate change in the context of women's reproductive health as a public health issue, a social justice issue, a human rights issue, an economic issue, a political issue, and a gender issue that needs our attention now for the health and well-being of this and future generations. FIGO joins a broad coalition of international researchers and the medical community in stating that the current climate crisis presents an imminent health risk to pregnant people, developing fetuses, and reproductive health, and recognizing that we need society-wide solutions, government policies, and global cooperation to address and reduce contributors, including fossil fuel production, to climate change.

Associations between ambient air pollution and IVF outcomes in a heavily polluted city in China

RESEARCH QUESTION

Is air pollution related to IVF outcomes in a heavily polluted city in China?

DESIGN

A retrospective cohort study of 8628 fresh, autologous IVF cycles was conducted for the first time at the Reproductive Medicine Center of The Third Affiliated Hospital of Zhengzhou University between May 2014 and December 2018 (oocyte retrieval date). The exposure was divided into four periods (gonadotrophin injection to oocyte retrieval [P1], oocyte retrieval to embryo transfer [P2], 1 day after embryo transfer to embryo transfer +14 days [P3] and gonadotrophin injection to embryo transfer +14 days [P4]) and four levels (Q1-Q4 according to their 25th, 50th and 75th percentiles).

RESULTS

An interquartile range increase (Q2 versus Q1) in particulate matter ≤10 µm (PM10) during P3 and P4 and sulphur dioxide (SO₂) during P3 significantly decreased the clinical pregnancy rate (adjusted odds ratio [aOR] 0.81, 95% confidence interval [CI] 0.71-0.92 for PM10 of P3; aOR 0.87, 95% CI 0.76-1.00 for PM10 of P4; aOR 0.82, 95% CI 0.73-0.93 for SO₂ of P3). In addition, PM10 was associated with an increased biochemical pregnancy rate (Q3 versus Q1: aOR 1.55, 95% CI 1.09-2.19 for PM10 of P1) and decreased live birth rate (Q2 versus Q1: aOR 0.88, 95% CI 0.77-0.99 for PM10 of P3). The multivariate regression results were consistent with that of multiple treatments propensity score method (PSM) for SO₂ pollutants in P3 and PM10 pollutants in P4.

CONCLUSION

From the early follicular stage to the pregnancy test period, high concentrations of PM10 and SO₂ may have a negative impact on IVF treatment outcomes in the study area.

The effect of short term exposure to outdoor air pollution on fertility

BACKGROUND

There is evidence to suggest that long term exposure to air pollution could be associated with decreased levels of fertility, although there is controversy as to how short term exposure may compromise fertility in IVF patients and what windows of exposure during the IVF process patients could be most vulnerable.

METHODS

This prospective cohort study aimed to evaluate the impact of acute exposure that air pollution have on reproductive outcomes in different moments of the IVF process. Women undergoing IVF living in Barcelona were recruited. Individual air pollution exposures were modelled at their home address 15 and 3 days before embryo transfer (15D and 3D, respectively), the same day of transfer (D0), and 7 days after (D7). The pollutants modelled were: PM2.5 [particulate matter (PM) ≤2.5 μm], PMcoarse (PM between 2.5 and 10μm), PM10 (PM≤10 μm), PM2.5 abs, and NO2 and NOx. Outcomes were analyzed using multi-level regression models, with adjustment for co-pollutants and confouding factors. Two sensitivity analyses were performed. First, the model was adjusted for subacute exposure (received 15 days before ET). The second analysis was based on the first transfer performed on each patient aiming to exclude patients who failed previous transfers.

RESULTS

One hundred ninety-four women were recruited, contributing with data for 486 embryo transfers. Acute and subacute exposure to PMs showed a tendency in increasing miscarriage rate and reducing clinical pregnancy rate, although results were not statistically significant. The first sensitivity analysis, showed a significant risk of miscarriage for PM2.5 exposure on 3D after adjusting for subacute exposure, and an increased risk of achieving no pregnancy for PM2.5, PMcoarse and PM10 on 3D. The second sensitivity analysis showed a significant risk of miscarriage for PM2.5 exposure on 3D, and a significant risk of achieving no pregnancy for PM2.5, PMcoarse and PM10 particularly on 3D. No association was observed for nitrogen dioxides on reproductive outcomes.

CONCLUSIONS

Exposure to particulate matter has a negative impact on reproductive outcomes in IVF patients. Subacute exposure seems to increase the harmful effect of the acute exposure on miscarriage and pregnancy rates. Nitrogen dioxides do not modify significantly the reproductive success.

Increased Incidence of Dysmenorrhea in Women Exposed to Higher Concentrations of NO, NO2, NOx, CO, and PM2.5: A Nationwide Population-Based Study

Background: Air pollution is speculated to affect the reproductive health of women. However, a longitudinal association between exposure to air pollution and dysmenorrhea has not been identified, which this study aimed to examine this point.

Methods: Two nationwide databases, namely the Taiwan Air Quality Monitoring database and the Taiwan National Health Research Institutes database were linked. Women with a history of dysmenorrhea (International Classification of Disease, Ninth Revision, Clinical Modification code 625.3) before 2000 were excluded. All participants were followed from January 1, 2000 until the diagnosis of dysmenorrhea, withdrawal from National Health Insurance, or December 31, 2013. Furthermore, air pollutants were categorized into quartiles with three cut-off points (25th, 50th, and 75th percentiles). The Cox regression model was used to calculate the hazard ratios of dysmenorrhea.

Results: This study enrolled 296,078 women. The mean concentrations of yearly air pollutants were 28.2 (±12.6) ppb for nitric oxides (NO_x), 8.91 (±7.93) ppb for nitric oxide (NO), 19.3 (±5.49) ppb for nitrogen dioxide (NO₂), 0.54 (±0.18) ppm for carbon monoxide (CO), and 31.8 (±6.80) μg/m³ for PM_2.5. In total, 12,514 individuals developed dysmenorrhea during the 12-year follow-up. Relative to women exposed to Q1 concentrations of NO_x, women exposed to Q4 concentrations exhibited a significantly higher dysmenorrhea risk [adjusted hazard ratio (aHR)= 27.9, 95% confidence interval (CI) = 21.6–31.3]; similarly higher risk was found for exposure to NO (aHR = 16.7, 95% CI = 15.4–18.4) and NO₂ (aHR = 33.1, 95% CI = 30.9–37.4). For CO, the relative dysmenorrhea risk in women with Q4 level exposure was 28.7 (95% CI = 25.4–33.6). For PM_2.5, women at the Q4 exposure level were 27.6 times (95% CI = 23.1–29.1) more likely to develop dysmenorrhea than those at the Q1 exposure level.

Conclusion: Our results showed that women would have higher dysmenorrhea incidences while exposure to high concentrations of NO, NO₂, NO_x, CO, and PM_2.5.

Association of exposure to ambient air pollution with ovarian reserve among women in Shanxi province of north China

Air pollution has been an important risk factor for female reproductive health. However, epidemiological evidence of ambient air pollution on the predictor for ovarian reserve (antral follicle count, AFC) is deficient. We aim to comprehensively evaluate the association of long-term exposure to ambient air pollution with AFC among women of reproductive age in Shanxi of north China. 600 women with spontaneous menstrual cycle, not using controlled ovarian stimulation, were enrolled in the retrospective study. Two distinct periods of antral follicle development were designed as exposure windows. Generalized linear model was employed to estimate the change of AFC associated with exposure of atmospheric pollutants (SO₂, NO₂, PM₁₀, PM_2.5, CO and O₃). Stratification analysis based on age (<30, ≥30 years), university degree (yes, no), years of exposure (2013-2016, 2017-2019) and duration of infertility (<2, 2-5, >5 years) along with two pollutants model were employed to further illustrate the association. We found every 10 μg/m³ increase in SO₂ concentration level during the entire development stage of antral follicle was associated with a -0.01 change in AFC (95% confidence interval: -0.016, -0.002) adjusting for the confounders including age, BMI, parity and infertility diagnosis factors. The significant association of increased SO₂ level with decreased AFC was particularly observed during the early transition from primary follicle to preantral follicle stage by 10 μg/m³ increase in SO₂ exposure level with a -0.01 change (95% CI: -0.015, -0.002) in AFC. The negative association was pronounced among women aged ≥30 years old, and also significant in two pollutants model after adjusting the confounders. No significant associations between other air pollutants and AFC were observed. Our finding suggests that long-term exposure to air pollutant SO₂ is associated with lower AFC, raising our concern that atmospheric SO₂ exposure may have potential adverse impact on women ovarian reserve.

Ambient air pollutant exposure and in vitro fertilization treatment outcomes in Zhengzhou, China

OBJECTIVE

To study the association between ambient air pollutant exposure during the follicular phase and in vitro fertilization (IVF) outcomes.

DESIGN

A single-center retrospective analysis.

SETTING

Henan Province, China.

PATIENTS

Patients (n = 6659) living in Zhengzhou, Henan Province in central China who underwent their first IVF cycle at the First Affiliated Hospital of Zhengzhou University between 2013 and 2019 were included for analysis.

INTERVENTION

None.

MAIN OUTCOME MEASURE

The relationships between PM_2.5, PM₁₀, and AQI (Air Quality Index) with IVF outcomes during the follicular phase (period I, 85 days before oocyte retrieval; period II, gonadotrophin start to oocyte retrieval).

RESULTS

Compared with the bottom tertile, exposure to the top PM_2.5 and PM₁₀ tertiles during period I was associated with decreased clinical pregnancy (PM_2.5: adjusted odds ratio [OR], 0.838%, and 95% confidence interval [CI], 0.723 and 0.971; PM₁₀: adjusted OR, 0.818%, and 95% CI, 0.705 and 0.950), and decreased live birth rate (PM_2.5: adjusted odds ratio [OR], 0.852%, and 95% confidence interval [CI], 0.736 and 0.987; PM₁₀: adjusted OR, 0.850%, and 95% CI, 0.733 and 0.986), and exposure to the top PM_2.5 tertile during period II adversely affected clinical pregnancy and the live birth rate (adjusted OR, 0.824%, and 95% CI, 0.711 and 0.955; adjusted OR, 0.817%, and 95% CI, 0.706 and 0.945). Compared with the bottom PM₁₀ tertile, exposure to the middle PM₁₀ tertile in period II showed decreased clinical pregnancies and live births (adjusted OR, 0.844; 95% CI, 0.729 and 0.978, adjusted OR, 0.846; 95% CI, 0.731 and 0.979). The PM₁₀ level during period II of the follicular phase tend to adversely affect live birth rate, but the tendency did not reach significance (P = 0.051).

CONCLUSION

Exposure to PM_2.5 and PM₁₀ before oocyte retrieval has an adverse effect on IVF outcomes.

CAPSULE

Exposure to PM_2.5 and PM₁₀ before oocyte retrieval has an adverse effect on IVF outcomes.

Elevated levels of nitrous dioxide are associated with lower AMH levels: a real-world analysis

STUDY QUESTION

Are there any associations between environmental pollutants and ovarian reserve, expressed by anti-Mullerian hormone (AMH) serum levels?

SUMMARY ANSWER

In this first real-world approach to demonstrate the relationship between air pollutants and serum AMH levels, adverse associations were observed for nitrogen dioxide (NO2) but not with particulate matter.

WHAT IS KNOWN ALREADY

In recent years, air pollution has emerged as a potential disrupter to the homeostasis of physiological hormones, possibly affecting human reproduction. Although the influence of age and smoking on AMH levels is largely accepted, the relationship between AMH and the environment has not currently been established.

STUDY DESIGN, SIZE, DURATION

A longitudinal, observational, retrospective, real-world study was carried out, including all AMH measurements performed in a single laboratory from January 2007 to October 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum AMH data were connected to patients' age and residential address, to include air pollution data after geo-localisation. The air pollution considered daily particulate matter (PM) and NO2 values.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1463 AMH measurements were collected (mean 1.94 ng/ml, median 0.90 ng/ml). AMH was inversely related to patients' age in women older than 25 years (adjusted R-squared 0.120, P < 0.001), but not in those younger than 25 years (adjusted R-squared 0.068, P = 0.055). AMH levels were inversely related to environmental pollutants, such as PM10 (Rho = -0.088, P = 0.001), PM2.5 (Rho = -0.062, P = 0.021) and NO2 (Rho = -0.111, P < 0.001). After subdividing the dataset into quartiles for PM10 and PM2.5, the influence of age on AMH serum levels was found to be a stronger influence than that exerted by PM (P = 0.833 and P = 0.370, respectively). On the contrary, considering NO2 quartiles, higher AMH levels were observed in third quartile compared to fourth quartile, even after adjustment for age (P = 0.028), indicating a stronger influence of NO2 exposure on AMH serum levels. Considering an AMH cut-off of 0.3 ng/ml, a significant higher frequency of women with severe ovarian reserve reduction in the fourth quartile was shown only for NO2 (P = 0.010).

LIMITATIONS, REASONS FOR CAUTION

Several limitations should be underlined, such as the lack of information about work and life habits of each patient and the retrospective nature of the analysis performed on real-world data.

WIDER IMPLICATIONS OF THE FINDINGS

Although the genetic component is highly predictive for defining the ovarian reserve at birth, potentially modifiable environmental factors could influence the rate of decline in AMH and ovarian reserve during adulthood.

STUDY FUNDINGCOMPETING INTEREST(S)

Authors have neither funding nor competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Winter Air Pollution from Domestic Coal Fired Heating in Ulaanbaatar, Mongolia, Is Strongly Associated with a Major Seasonal Cyclic Decrease in Successful Fecundity

Pollution of the environment is increasing and threatens the health and wellbeing of adults and children around the globe. The impact of air pollution on pulmonary and cardiovascular disease has been well documented, but it also has a deleterious effect on reproductive health. Ulaanbaatar, the capital city of Mongolia, has one of the highest levels of air pollution in the world. During the extreme winters when temperatures routinely fall below -20 °C the level of air pollution can reach 80 times the WHO recommended safe levels. Heating mainly comes from coal, which is burned both in power stations, and in stoves in the traditional Ger housing. We studied the impact of air pollution on conception rates and birth outcomes in Ulaanbaatar using a retrospective analysis of health data collected from the Urguu Maternity hospital in Ulaanbaatar, Mongolia. Daily levels of SO₂, NO₂, PM₁₀, and PM_2.5 were collected from the government Air Quality Monitoring Stations in Ulaanbaatar for the same period as the study. In January, the month of highest pollution, there is a 3.2-fold decrease in conceptions that lead to the successfully delivered infants compared to October. The seasonal variations in conceptions resulting in live births in this study in Ulaanbaatar are shown to be 2.03 ± 0.20 (10-sigma) times greater than those in the Denmark/North America study of Wesselink et al., 2020. The two obvious differences between Ulaanbaatar and Europe/North America are pollution and temperature both of which are extreme in Ulaanbaatar. The extreme low temperature is mitigated by burning coal, which is the main source of domestic heat especially in the ger districts. This drives the level of pollution so the two are inextricably linked. Infants conceived in the months of June-October had the greatest cumulative PM_2.5 pollution exposure over total gestation, yet these were also the pregnancies with the lowest PM_2.5 exposure for the month of conception and three months prior to conception. The delivered-infant conception rate shows a markedly negative association with exposure to PM_2.5 prior to and during the first month of pregnancy. This overall reduction in fecundity of the population of Ulaanbaatar is therefore a preventable health risk. It is of great consequence that the air pollution in Ulaanbaatar affects health over an entire lifespan including reproductive health. This could be remedied with a clean source of heating.