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.

Superfertility and subfertility in patients with recurrent pregnancy loss: A comparative analysis of clinical characteristics and etiology based on differences in fertile ability

This study aimed to elucidate the etiologies of and risk factors for recurrent pregnancy loss (RPL) according to fertile ability, focusing on the differences between superfertile and subfertile patients. This retrospective observational study included 828 women with RPL between July 2017 and February 2020. Patients were divided into three groups based on time to pregnancy (TTP): superfertile (SUP) (TTP ≤3 months for all previous pregnancies), subfertile (SUB) (previous TTP ≥12 months and use of assisted reproductive technology [ART]), and Normal (N) (TTP >3 or <12 months without ART). All patients were assessed for uterine anatomy, antiphospholipid antibodies (APAs), thyroid function, and thrombophilia. Of the 828 patients, 22%, 44%, and 34% were assigned to the SUP, SUB, and N groups, respectively. The mean ages were 33.9, 38.2, and 35.9 years in the SUP, SUB, and N groups, respectively, revealing a significant difference (P < 0.001). The anti-CL β2GPI antibody positivity rate was significantly higher in the SUP group (4.6%) than in the N group (0.8%; P = 0.016). The prevalence of APA positivity was lowest in the N group. Overall, the clinical characteristics and etiologies of RPL associated with superfertility and subfertility were strikingly similar, with comparable positivity rates after adjusting for maternal age. Further investigation including chromosomal analysis of products of conception is needed to elucidate the clinical impact of differences in fertility on patients with RPL.

Time to live birth: towards a common agreement

The major purpose of a couple at the first infertility appointment is to get a healthy baby as soon as possible. From diagnosis and decision on which assisted reproduction technique (ART) and controlled ovarian stimulation, to the selection of which embryo to transfer, the dedicated team of physicians and embryologists puts all efforts to shorten the time to pregnancy and live birth. Time seems thus central in assisted reproduction, and we can conveniently use it as a measure of treatment efficiency. How can we measure time to live birth? What timelines do we need to consider to evaluate efficiency? In this paper, we will discuss the importance of "Time" as a fundamental parameter for measuring ART success.

Congenital heart disease and the risk of impaired fertility: A Danish nationwide cohort study using time to pregnancy

BACKGROUND

The number of women with congenital heart disease (CHD) becoming pregnant are increasing. Although menstrual irregularities appear to occur more often in these patients, knowledge on their fertility is limited. In this nationwide cohort study, we evaluated the risk of impaired fertility in women with CHD compared with unaffected women using time to pregnancy (TTP).

METHODS

The Danish National Birth Cohort (DNBC) of pregnant women constituted the study population. Information on TTP and use of medically assisted reproduction (MAR) treatment was reported at a first trimester interview. Women with CHD were identified by linkage to the Danish National Patient Registry. TTP was divided into three categories; 0-5 months, 6-12 months (i.e. subfertile), and > 12 months or use of MAR treatment (i.e. infertile). Relative risk ratios (RRR) for subfertility and infertility with 95% confidence intervals were estimated using multinomial logistic regression.

RESULTS

Among 93,832 pregnancies in 84,922 women, CHD was diagnosed in 333 women (0.4%), contributing with 360 pregnancies. The CHD was of simple complexity in 291 women (87.4%). No association was found between CHD and longer TTP (RRR of 1.02 (95% CI: 0.75-1.40) for subfertility, and RRR of 0.86 (95% CI: 0.61-1.20) for infertility). Similar was observed when comparing women with simple CHD and unaffected women. The number of women with complex CHD was too low for evaluation.

CONCLUSIONS

Women with CHD had no increased risk of impaired fertility, assessed by TTP, when compared with unaffected women. Separate analysis of women with complex CHD was hampered by low numbers.

Time to pregnancy and perinatal outcomes in a cohort of spontaneous pregnancies

BACKGROUND

Obstetric and perinatal outcomes depend not only on care during pregnancy, as there is an increasing evidence of their relationship with preexisting conditions. Woman's age and time to pregnancy (TTP) have been related to the prognosis in reproductive success, but TTP could influence fetal well-being and newborn. According to the World Health Organization, 48 million couples have subfertility globally.

METHODS

We analyzed the relationship between TTP and obstetric (premature labor, preeclampsia…), labor (type of delivery, postpartum hemorrhage…), and neonatal outcomes (low birth weight…) in a cohort of 190 spontaneous gestations. Subfertility is a disease defined by the failure to achieve a pregnancy after 12 months of regular unprotected sexual intercourse.

RESULTS

TTP was >12 months in 23.1 % (95 % CI = 17.57-29.55), however, no correlation was found with the perinatal outcomes (p = 0.24). We observed that 45.2 % of subfertile women had obstetric complications, 13.2 % labor complications, and 34.2 % neonatal complications, whereas non-subfertile women had 29.4 %, 21.0 %, and 21.0 %, respectively. Half of pregnancies have at least one adverse outcome, and obstetric complications were the most frequent.

CONCLUSION

Subfertility condition may appear in up to a fifth of our couples. Subfertility may behave as a mild risk factor for adverse perinatal outcomes. Obstetric or perinatal complication may be expected in up to half of the cases. Subfertile women ≥ 35 years of age have a 3-fold increase in their risk of having an obstetric complication when compared to non-subfertile women of the same age.

The associations between low abundance of Mycoplasma hominis and female fecundability: a pregnancy-planning cohort study

Objective

To explore the impact of pre-pregnancy vaginal Mycoplasma hominis (M. hominis) colonization of low abundance on female fecundability.

Methods

In total, 89 females participating in a pre-pregnancy health examination program were included, and their pregnancy outcomes were followed up for 1 year. Vaginal swabs were collected, 16S rRNA genes were sequenced, and M. hominis colonization was confirmed by qPCR. Cox models were used to estimate the fecundability odds ratio (FOR) for women with M. hominis.

Results

The prevalence of M. hominis was 22.47% (20/89), and the abundance was relatively low (the cycle thresholds of the qPCR were all more than 25). In terms of the vaginal microbiome, the Simpson index of the positive group was significantly lower than that of the negative group (P = 0.003), which means that the microbiome diversity appeared to increase with M. hominis positivity. The relative abundance of M. hominis was negatively correlated with Lactobacillus crispatus (rho = − 0.24, P = 0.024), but positively correlated with Gardnerella vaginalis, Atopobium vaginae and Prevotella bivia (P all < 0.05). The cumulative one-year pregnancy rate for the M. hominis positive group was lower than that in the negative group (58.96% vs 66.76%, log-rank test: P = 0.029). After controlling for potential confounders, the risk of pregnancy in the M. hominis positive group was reduced by 38% when compared with the positive group (FOR = 0.62, 95% CI: 0.42–0.93).

Conclusion

The vaginal colonization of M. hominis at a low level in pre-pregnant women is negatively correlated with female fecundability.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02545-7.

Association between halitosis and female fecundability in China: a prospective cohort study

Background

Periodontal diseases and poor oral hygiene are potentially associated with decreased female fecundability. Fecundability refers to the probability of conception during a given period measured in months or menstrual cycles. This study aims to examine whether halitosis is associated with female fecundability in a large sample of Chinese women who planned to be pregnant.

Methods

In 2012, a total of 6319 couples came for preconception care in eight districts in Shanghai, China and were followed by telephone contact. Three thousand nine hundred fifteen women who continued trying to be pregnant for up to 24 months remained for final statistical analyses. Halitosis was self-reported at the preconception care visit. Time to pregnancy (TTP) was reported in months and was censored at 24 months. Fecundability ratio (FR) was defined as the ratio of probability of conception among those with and without halitosis. FR and 95% confidence interval (CI) were estimated using the discrete-time Cox model.

Results

80.1 and 86.1% of women had self-reported clinically confirmed pregnancy within 12 and 24 months, respectively. Halitosis was reported in 8.7% of the women. After controlling for potential confounders, halitosis was associated with a reduced probability of spontaneous conception (for an observation period of 12 months: adjusted FR 0.82, 95% CI 0.72–0.94; for an observation period of 24 months: adjusted FR 0.84, 95% CI 0.74–0.96).

Conclusions

Halitosis is associated with reduced fecundability in Chinese women.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04315-1.

Measuring success in IVF is a complex multidisciplinary task: time for a consensus?

The goal of an IVF cycle is the birth of at least one baby per intention to treat. However, IVF cannot confer competence on an embryo, but only can provide each couple with a safe treatment to meet a predetermined chance of success. This commentary highlights how clinical, financial and patient-centred perspectives should be included in the definition of success in IVF. The primary outcome, which is the cumulative live birth delivery rate per intention to treat, must always be complemented by analyses of risks, costs and time invested, as well as by measures of patient satisfaction. Finally, it is essential, whenever clinical conditions exist, to limit treatment discontinuation after failed attempts. Constant monitoring of the data is pivotal and must be adjusted for patient characteristics and compared with national and international registers. The authors aimed to review all these aspects and highlight the points that are still open for discussion. Is it time for a consensus?

Association between exposure to airborne particulate matter less than 2.5 μm and human fecundity in China

BACKGROUND

Whether exposure to airborne particulate matter less than 2.5 μm (PM_2.5) could impact human fecundity is unclear. We aimed to evaluate the potential impact of PM_2.5 exposure on time to pregnancy (TTP) and the prevalence of infertility in the general Chinese population.

METHOD

We collected reproductive information, sociodemographic characteristics, and lifestyle data of 10,211 couples at risk of pregnancy from a large-scale community-based fertility survey in China. Then, we estimated each participant's 1-year, 3-year, and 5-year average PM_2.5 exposure levels based on remote sensing information. After adjusting for demographic, lifestyle, and environmental co-variables, discrete-time Cox regression models were used to estimate the fecundability odds ratio (FOR) per 10 μg/m³ change of PM_2.5. We also estimated the odds ratio (OR) of infertility per 10 μg/m³ change of PM_2.5, using logistic regression models.

FINDINGS

Among the 10,211 couples, 6,875 (67%) had conceived spontaneously, with a median TTP of 5 months (interquartile range: 2-10 months). The median PM_2.5 exposure was 56.8 μg/m³, with a wide range of 9.2-93.5 μg/m³. In Cox regression models, each increase of 10 μg/m³ in the 1-year average PM_2.5 exposure was associated with a significant decrease in fecundity by 11% (FOR: 0.89; 95% confidence interval [CI]: 0.86-0.92). In logistic regression models, it was also associated with an 20% increased likelihood of infertility (OR: 1.20; 95% CI: 1.13-1.27).

CONCLUSION

PM_2.5 exposure was associated with reduced human fecundity, presented by a longer TTP and higher odds of infertility, which might explain the increased infertility rates in areas with heavy PM_2.5 pollution.

Long-term outcome of patients undergoing in-vitro fertilisation in France: The outcome study

The Outcome study examines the fate of 4083 patients beginning IVF in 41 IVF centres, between January 2010 and December 2013. Cumulative live birth rate per patient (CLBR), the best reflection of IVF efficacy, is rarely presented in publications as it requires long-term follow-up, including all successive cycles, and pregnancies outcome. Analysis of international publications shows an average CLBR of 41.6 % and a drop-out rate of 49.5 %, both greatly varying by country and IVF centres. Because of the frequency with which patients change centre (8%), the Outcome study distinguishes patients with a past history of IVF in another centre (CLBR=47.2 %) and patients undergoing their first true cycle (CLBR=56.4 %). Survival techniques by Competing Risk, intended to take account of drop-out and lost to follow-up, assessed the overall CLBR as being 65.4 %. Differences in performance between centres are considerable for both CLBR (32-64%) and Performance Index, taking account of the number of cycles required to achieve a pregnancy (2-5). Multiple variance logistic regression analysis shows that the indicators influencing performance are age, parity, number of oocytes, smoking habit and overweight. These indicators are independent each other and are influencing performance in a high significant way. After adjusting for these indicators, the differences between centres are reduced but remain large and very significant. No centre appears to have specific expertise in the management of patients with adverse indicators. The Outcome study therefore confirms that the large differences in performance between centres are not explained by a difference in the treated population.

Association of income and education with fecundability in a North American preconception cohort

PURPOSE

The purpose of this study is to evaluate socioeconomic determinants of fecundability.

METHODS

Among 8654 female pregnancy planners from Pregnancy Study Online, a North American prospective cohort study (2013-2019), we examined associations between socioeconomic status and fecundability (the per-cycle probability of conception). Information on income and education was collected via baseline questionnaires. Bimonthly follow-up questionnaires were used to ascertain pregnancy status. We estimated fecundability ratios (FRs) and 95% confidence intervals (CIs) using proportional probabilities regression, controlling for potential confounders.

RESULTS

Relative to an annual household income of greater than or equal to $150,000, adjusted FRs were 0.91 (95% CI: 0.83-1.01) for less than $50,000, 0.99 (95% CI: 0.92-1.07) for $50,000-$99,000, and 1.09 (95% CI: 1.01-1.18) for $100,000-$149,000. FRs for less than 12, 13-15, and 16 years of education, relative to greater than or equal to 17 years, were 0.90 (95% CI: 0.76-1.08), 0.84 (95% CI: 0.78-0.91), and 0.89 (95% CI: 0.84-0.95), respectively. Slightly stronger associations for income and education were seen among older women.

CONCLUSIONS

Lower levels of education and income were associated with modestly reduced fecundability. These results demonstrate the presence of socioeconomic disparities in fecundability.

The association between iodine intake and semen quality among fertile men in China

BACKGROUND

Iodine intake is essential in the production of thyroid hormone but very few foods are rich in it. Iodine deficiency or excess iodine level may both lead to thyroid disorders, which further affects human fertility function. The objective of this study is to investigate the relationship between iodine intake and seminal parameters among fertile men in China.

METHODS

A total of 1098 couples were recruited by trained physicians at different family planning service stations in 2015. Semen and iodine samples were obtained from male respondents. A questionnaire survey inquired about demographic information from couples. The main outcome variables of semen quality were semen volume, semen concentration, semen motility, and sperm count, and time to pregnancy. Urinary iodine concentration (UIC) was used to measure iodine levels for male respondents. Ordinary least squared regressions and logistic regressions were performed to estimate the association between iodine intake level and semen quality parameters.

RESULTS

Male respondents with deficient or excess iodine levels had a 5% higher semen volume relative to those with optimal iodine intake (p < 0.1). Suboptimal iodine intake was negatively associated with semen concentration and semen counts (p < 0.01). Longer time of pregnancy was observed in iodine deficiency and excess group than those in the optimal group (p < 0.01).

CONCLUSION

In general, iodine deficiency and excess were both associated with decreasing semen quality parameters in male respondents.

Pregnancy, time to pregnancy and obstetric outcomes among female childhood cancer survivors: results of the DCOG LATER-VEVO study

Purpose

To evaluate pregnancy rates, time to pregnancy (TTP) and obstetric outcomes in female childhood cancer survivors (CCSs) and to identify specific diagnosis- and treatment-related factors associated with these outcomes.

Methods

The study is part of the DCOG LATER-VEVO study, a nationwide multicenter cohort study evaluating fertility among long-term Dutch female CCSs. Data were collected by questionnaire. The current study included 1095 CCSs and 812 controls, consisting of sisters of CCSs and a random sample of women from the general population.

Results

Among the subgroup of women who ever had the desire to become pregnant, the chance of becoming pregnant was significantly lower for CCSs than controls (OR 0.5, 95%CI 0.4–0.8). Moreover, TTP was 1.1 times longer for CCSs compared to controls (p = 0.09) and was significantly longer in survivors of CNS and renal tumours. Overall, no differences were found between CCSs and controls regarding the probability of ever having had a miscarriage, still birth, or induced abortion. However, CCSs had a significantly increased risk of delivering preterm (OR 2.2, 95%CI 1.3–3.7) and delivering via caesarean section (OR 1.8, 95%CI 1.2–2.6). Treatment with lower abdominal/pelvic radiotherapy was strongly associated with several adverse obstetric outcomes.

Conclusion

CCSs are less likely to have ever been pregnant. Among those who do become pregnant, certain subgroups of CCSs are at increased risk of longer TTP. Moreover, as pregnant CCSs, especially those treated with lower abdominal/pelvic radiotherapy, are more likely to develop various adverse obstetric outcomes, appropriate obstetric care is highly advocated.

Electronic supplementary material

The online version of this article (10.1007/s00432-020-03193-y) contains supplementary material, which is available to authorized users.

Daily perceived stress and time to pregnancy: A prospective cohort study of women trying to conceive

BACKGROUND

Prior studies among women with impaired fecundity have consistently demonstrated a positive association between daily perceived stress and the ability to conceive. However, the effects of daily stress on time to pregnancy (TTP) among women with proven fertility is not known.

MATERIALS AND METHODS

One hundred and forty-three women ages 18-35, in a relationship of proven fertility, who desired to conceive were included in the analysis. Daily diaries recording perceived stress (scale 0-10) were completed for up to 7 menstrual cycles or until pregnancy. Cox proportional hazards regression models were used to estimate the association between time-varying perceived stress tertiles (high [>4.1-7.2], moderate [>2.7-4.1], and low [0.1-2.7]) and adjusted fecundability odds ratio (aFOR), 95% confidence intervals (CI), after taking into account age, parity, education, time-varying caffeine and alcohol intake, fertility awareness tracking, and cycle intent to conceive.

RESULTS

Among the 111 participants who completed daily diaries, 90 (81.1%) conceived. Women reporting high or moderate stress, versus low stress, had no difference in probability of achieving pregnancy (aFOR: 1.11 [95% CI: 0.58, 2.14]; and aFOR: 1.37 [0.71, 2.67]), respectively. Additional adjustment for intercourse frequency during narrow fertile window, or narrowing exposure focus to pre-ovulatory or pre-implantation stress did not appreciably alter the estimates.

CONCLUSION

Daily perceived stress was not adversely associated with TTP among women with proven fertility. While a growing body of evidence supports adverse effects of more severe stressful life events on female reproductive function, moderate psychological stress, commonly referred to as eustress, among relatively healthy women with proven fertility does not appear to adversely impact TTP.

Mining leachate contamination and subfecundity among women living near the USA-Mexico border

The contamination of the Sonora River with 40,000 m³ of toxic leachate released from a copper mine on August 6, 2014, was considered the worst environmental disaster of the mining industry in Mexico, exceeding safety levels in the concentrations of heavy metals and arsenic. To explore the potential association of the toxic release with subfecundity, by comparing time to pregnancy (TTP) of women with different levels of exposure at municipalities located along the Sonora River watershed, just 35 km south of the Arizona-Mexico border. Data from 235 pregnancies were included in a retrospective cohort study. Exposure was measured whether pregnancy occurred before or after the disaster and included a non-exposed community outside the watershed. Pregnancies were also compared between communities according to the concentration-level gradient of water pollutants found in the river. Fecundability odds ratios (fORs) were calculated using discrete time analogue of Cox's proportional hazard models. Multiple analysis included all pregnancies with TTP of no more than 12 months, only first-time pregnancy, or excluding women with TTP = 1. The probability for pregnancy decreased after the disaster (fOR 0.55, 95% CI 0.31, 0.97), when the residency was located mid-or-downstream the watershed (fOR 0.37, 95% CI 0.15, 0.91), when reported chicken consumption, when mining was the father's occupation, and when surface water was reported to be used for crop irrigation and for animal consumption. There was a decrease in fecundity on women exposed to the contaminated river. There is a need for more studies to prove these findings and to broaden the knowledge of other possible adverse health effects associated with this environmental disaster.

A systematic review: Impact of endocrine disrupting chemicals exposure on fecundity as measured by time to pregnancy

BACKGROUND

Emerging scientific evidence suggests that exposure to environmental pollutants is associated with negative effects on fecundity as measured by time to pregnancy (TTP).

OBJECTIVES

To conduct a systematic review of the literature on the association between selected endocrine disrupting chemicals (EDCs), and fecundity as measured by TTP in humans. Compounds included in this review are: brominated flame retardants (BFRs) such as hexabromocyclododecane, tetrabromobiphenol A and polybrominated diphenyl ethers; organophosphates flame retardants (OPFRs); and phthalates.

METHODS

Scopus, MEDLINE via Ebscohost and EMBASE databases were searched for articles exploring the relationships between selected EDCs and fecundity as measured by time to pregnancy. We assessed the quality of included studies and evidence for causality was graded using the criteria developed by the World Cancer Research Fund.

RESULTS

14 studies of 191 full-text articles assessed for eligibility were included for qualitative synthesis. Five studies examined BFRs and 10 studies examined phthalates. Among the fourteen, one study assessed both BFRs and phthalates. There were no studies which investigated fecundity as measured by TTP on HBCD, TBBPA, or OPFRs. We recorded plausible fecundity outcomes as measured by TTP related to some of these EDCs. BFRs or phthalates increased TTP. However, results were inconsistent.

CONCLUSION

We recorded mostly weak associations between exposure to selected EDCs and fecundity. However, evidence was considered limited to conclude a causal relationship due to inconsistency of results. The health risks posed by these chemicals in exposed populations are only beginning to be recognized and prospective measurement of the environmental effects of the chemicals in large cohort studies are urgently needed to confirm these relationships and inform policies aimed at exposure prevention.

Exposure to tetrachloroethylene-contaminated drinking water and time to pregnancy

BACKGROUND

The synthetic solvent tetrachloroethylene (PCE), commonly used in dry cleaning operations, is a human neurotoxicant and carcinogen. However, its effect on reproduction is poorly understood, as prior studies have been limited to small occupational cohorts. We examined the association between PCE exposure from contamination of the public drinking water supply and time-to-pregnancy (TTP) in a cohort of mothers from Cape Cod, Massachusetts.

METHODS

The Cape Cod Family Health Study is a retrospective cohort study designed to examine the reproductive and developmental health effects of exposure to PCE-contaminated drinking water. Our analysis included 1565 women who reported 3826 planned pregnancies from 1949 to 1990. Women completed self-administered questionnaires that ascertained TTP for each of her pregnancies, regardless of the outcome, as well as residential history and demographic information. We utilized EPANET water distribution system modeling software and a leaching and transport model to assess PCE exposure for each pregnancy. We used log-binomial regression models to estimate relative risks (RR) and 95% confidence intervals (CI), adjusting for potential confounders. We performed a probabilistic bias analysis to examine the effect of outcome misclassification on our results.

RESULTS

Any cumulative PCE exposure before pregnancy was associated with a 15% reduction in risk of TTP > 12 months (RR = 0.85, 95% CI: 0.70, 1.03). However, women with the highest average monthly PCE exposure around the time of the pregnancy attempt (≥ 2.5 g) had increased risk of TTP > 12 months (RR = 1.36, 95% CI: 1.06, 1.76).

CONCLUSIONS

We found little evidence for long-term, cumulative adverse effects of PCE exposure on TTP, but high levels of PCE exposure around the time of the pregnancy attempt were associated with longer TTP. These associations may be underestimated due to the exclusion of unsuccessful pregnancy attempts from our study population, and may be biased by outcome and exposure misclassification given the long-term recall of TTP and use of a leaching and transport model to estimate PCE exposure.

The impact of maternal lifestyle factors on periconception outcomes: a systematic review of observational studies

The main risk factors for important reproductive health issues such as subfertility and perinatal mortality largely originate in the periconception period. To evaluate associations between modifiable maternal lifestyle factors and periconception outcomes, a systematic search was conducted for relevant studies published from 1990 to February 2017 on Embase, Medline, Web of Science, Cochrane database, PubMed and Google Scholar. The initial search identified 6166 articles, of which 49 studies were eligible for inclusion. Fecundity (the capacity to have a live birth) showed significant inverse associations with smoking, alcohol use and poor diet. Studies regarding time to pregnancy showed a decline in fecundity ratios (the monthly conception rate among exposed relative to unexposed couples) with increasing body mass index (BMI). Furthermore, risk of first-trimester miscarriage was found to be increased in smokers, alcohol and caffeine consumers, and with increasing BMI. Vitamin supplement use showed a decrease in this risk. This review demonstrates that maternal modifiable lifestyle factors affect periconception outcomes. If couples planning a pregnancy are more aware and supported to adopt healthy lifestyles during the periconceptional 'window of opportunity', short-term reproductive health as well as health in later life and even of future generations can be further improved.

Associations of female exposure to bisphenol A with fecundability: Evidence from a preconception cohort study

BACKGROUND

Human exposure to bisphenol A (BPA) is common. The reproductive toxicity of BPA has been well characterized. However, the impact of BPA exposure on fecundability in healthy women is less clear, and evidence from eastern countries is lacking.

OBJECTIVES

We aimed to prospectively assess the associations of BPA with female fecundability, as measured by time to pregnancy (TTP).

METHODS

From 2013 to 2015, we included 700 Chinese couples attempting pregnancy in two preconception care clinics and followed for 12 months or until a pregnancy occurred. The concentrations of BPA were determined in preconception urine samples of female partners. Cox's proportional models for discrete survival time were used to estimate fecundability odds ratios (FORs). Odds ratios (ORs) for infertility (TTP > 12 months) were estimated using logistic regression models.

RESULTS

After adjusting for potential confounders, each ln-unit increase in urinary concentrations of BPA was associated with a 13% reduction in fecundability (FOR = 0.87; 95% CI: 0.78, 0.98) and a 23% increase in odds of infertility (OR = 1.23; 95% CI: 1.00, 1.50). Women in the highest quartile of urinary BPA had a 30% reduction in fecundability (FOR = 0.70, 95% CI: 0.51, 0.96) and a 64% increase in odds of infertility when compared to those in the lowest quartile (OR = 1.64, 95% CI: 0.90, 2.98). The associations of urinary BPA concentrations with fecundability (FOR = 0.80, 95% CI: 0.67, 0.95) and infertility (OR = 1.43, 95% CI: 1.05, 1.93) were strengthened among women over 30 years of age.

CONCLUSIONS

Our results suggest that preconception concentrations of BPA in female urine were associated with decreased fecundability, particularly among women at older ages. These findings should be confirmed in future human studies.

The impact of FSH receptor polymorphism on time-to-pregnancy: a cross-sectional single-centre study

Background

Single nucleotide polymorphism of the follicle-stimulating hormone (FSH) receptor (FSHR) is an important marker of ovarian function. However, its role in female fecundity remains debatable. The aim of the study to assess the relationship of FSHR polymorphism of Serine/Serine, Asparagine/Asparagine and Asparagine/Serine variants directly against the time-to-pregnancy (TTP) in women.

Methods

Data were collected from 291 consecutive selected post-partum Caucasians using this criterion: ethnicity, age between 21 and 34-year-old new mothers and, 0–3 days after delivery of newborns in the Klaipeda University Hospital, Lithuania. Questionnaires on factors associated with conception were given to patients, and blood samples were collected for genomic DNA extractions as well as for analysis of follicle-stimulating hormone receptor gene polymorphism. Odds ratios (OR) and 95% confidence intervals (CI) for time-to-pregnancy were estimated by multivariate logistic regression. Women with unplanned pregnancies and those who received assisted reproductive technologies were not included in the study.

Results

After adjustment for other possible factors, increased risk for time-to-pregnancy of 12 or more months was associated with: Serine/Serine polymorphism variant (OR = 1.38, 95% CI 1.56–2.71, p = 0.007), age of 30 or more years (OR = 1.95, 95% CI 1.25–2.71, p = 0.015), gynaecological diseases in the past (OR = 2.21, 95% CI 1.12–5.74, p = 0.027), prior contraception use (OR = 1.87, 95% CI 1.14–3.64, p = 0.016), and fertility problems in the past (OR = 1.57, 95% CI 1.16–4.76, p = 0.019).

Conclusion

The results suggest a possible relationship of FSH receptor gene Serine/Serine variant for the lower possibility of conception during the first 12 months of planned conception.

Exposure to residential road traffic noise prior to conception and time to pregnancy

OBJECTIVES

To examine the association between residential road traffic noise and fecundity estimated by time to pregnancy (TTP).

DESIGN

We identified 65,201 mothers from the Danish National Birth Cohort with self-reported information on TTP collected through computer assisted telephone interviews. Road traffic noise was modelled at all historical addresses and expressed as time-weighted means for periods corresponding to individual TTP. Associations were analyzed using logistic regression for analyses of dichotomous outcomes and ordinal logistic regression for TTP in four categories, adjusting for maternal age at conception, disposable household income, education and air pollution (NO_x).

RESULTS

Ordinal logistic regression showed a 10dB increase in road traffic noise to be associated with a 8% increased risk of 6-12month TTP (95% CI:1.03; 1.12) whereas we found no statistically significant associations for ≥12months TTP (OR=1.04, 95% CI: 0.99; 1.09) when compared to 0-2months TTP. Similarly, when exploring TTP as a binary outcome we found a 10dB higher road traffic noise to be associated with a 5% higher risk of TTP of 6months or more (95% CI: 1.01; 1.08) as compared with <6months TTP, whereas when the cut-point was 12months TTP no association was found.

CONCLUSION

Road traffic noise was associated with an increased risk of 6-12month TTP, but not with risk of longer TTP, indicating that noise may have a small impact on sub-fecundity.

The study of waiting time to first pregnancy in the south of Iran: A parametric frailty model approach

BACKGROUND

Time to first pregnancy (TTFP) has never been studied in an Iranian setting. Lifestyle, occupational and environmental factors have been suggested to affect the female reproduction.

OBJECTIVE

This study was conducted to measure TTFP in the south of Iran and survey the effects of several similar factors on TTFP by frailty models.

MATERIALS AND METHODS

The data on TTFP were available for 882 women who were randomly selected from the rural population (the south of Iran). Only the first and the planned pregnancies of every woman were included. The data were collected retrospectively by using self-administered questionnaires. Frailty and shared frailty models were used to determine which factors had the highest impact on TTFP.

RESULTS

The median TTFP was 6.4 months and several factors were surveyed. However, only the age of marriage, height, maternal education and regularity of menstruation prior to conception were selected in the multivariable models.

CONCLUSION

Among the several factors which were included in the study, the result of frailty model showed that the height, age of marriage and regular menstruation seemed more notable predictors of TTFP.

Maternal exposure to extremely low frequency magnetic fields: Association with time to pregnancy and foetal growth

BACKGROUND

Data on reproductive and developmental effects of extremely low frequency magnetic fields (ELF MFs) are inconclusive. This study tested the hypothesis that maternal exposure to ELF MFs is associated with increased time to pregnancy (TTP), reduced birthweight or small for gestational age (SGA).

METHODS

The study cohort consisted of 373 mothers who gave birth between 1990 and 1994 in Kuopio University Hospital, Finland. To increase prevalence of high ELF MF exposure, women living in buildings near known ELF MF sources were included. Maternal exposure to ELF MF before and during pregnancy was assessed with short term measurements in residences and questionnaires. Associations between ELF MF exposure and TTP, low birth weight and SGA were analysed by logistic regression (or linear regression for continuous variables), adjusting for factors known to be associated with the selected pregnancy outcomes, such as maternal smoking, alcohol consumption and socioeconomic status.

RESULTS

The MF exposure of the mothers was slightly higher than in Finnish residences in general, but very high exposures (>0.4μT) were rare. No consistent association of ELF MF with TTP, birth weight or SGA was found.

CONCLUSIONS

ELF MF exposure is not likely to be associated with TTP or prenatal growth at residential exposure levels that were observable in this study.

Serum perfluoroalkyl acids and time to pregnancy in nulliparous women

BACKGROUND

Previous studies on the exposure to perfluoroalkyl acids (PFAAs) and female fertility have provided conflicting results. We aimed to investigate the association between several PFAAs and time to pregnancy among nulliparous women.

METHODS

From 2008 to 2013, we included 1372 women from the Aarhus Birth Cohort, Aarhus University Hospital, Denmark, who provided data on time to pregnancy and a blood sample before 20 gestational weeks. We measured the levels of 16 PFAAs in maternal serum and report data for seven compounds with quantifiable values in at least 50% of samples. Fecundability ratios according to PFAA levels (quartiles or continuous levels) were estimated by discrete-time survival analyses, adjusted for potential confounders. We further investigated the association between PFAAs and infertility (time to pregnancy>12 months or infertility treatment prior to the studied pregnancy) by multivariable logistic regression.

RESULTS

Median levels of perfluorooctane sulfonate and perfluorooctanoate were 8.3 and 2.0 ng/mL. Overall, no obvious associations were found between any PFAAs and fecundability or infertility. Adjusted fecundability ratios (95% confidence intervals) were 1.09 (0.92-1.29) for perfluorooctane sulfonate and 1.10 (0.93-1.30) for perfluorooctanoate (highest versus lowest quartile).

CONCLUSIONS

We found no evidence of an association between present serum levels of PFAAs and longer time to pregnancy or infertility in nulliparous women. This study further adds to the sparse knowledge on PFAAs besides perfluorooctane sulfonate and perfluorooctanoate.

Time to next pregnancy in spontaneous pregnancies versus treatment cycles in fertile patients with recurrent pregnancy loss

BACKGROUND

The current standard of care for management of patients with recurrent pregnancy loss is expectant management. However, the emotional impact of pregnancy losses and the urgency to conceive often leads couples to consider a variety of fertility treatments. The objective of this study is to report the time to next pregnancy and subsequent live birth and miscarriage rates in fertile patients with recurrent pregnancy loss (RPL) who choose to attempt spontaneous conception compared to those that opt to pursue fertility treatment.

METHODS

Retrospective cohort study of one hundred and fifty-eight fertile RPL patients treated at a university-based fertility center. Patients were followed for a minimum of 6 months. Patients were encouraged to attempt spontaneous conception, but allowed to initiate fertility treatments (ovarian stimulation, insemination, IVF or PGS) according to their preferences. Main outcome measures were time to next pregnancy and pregnancy outcome.

RESULTS

For those patients who achieved a spontaneous conception, 88% conceived within 6 months, with a median time of 2 months and range of 1-10 months. Patients using IUI, IVF and PGS conceived in a median of 3, 4 and 5 months, respectively. The live birth rate and clinical miscarriage rate was not improved with any fertility treatment.

CONCLUSIONS

In the fertile RPL patient population, there does not appear to be a benefit to proceeding directly with fertility treatment. Patients should be encouraged to attempt spontaneous conception for at least 6 months.

Male fertility following occupational exposure to dichlorodiphenyltrichloroethane (DDT)

BACKGROUND

The inconsistent epidemiological results of the endocrine disrupting effects of DDT fuel a harsh debate on its global ban.

OBJECTIVES

We tested the hypothesis that occupational exposure to dichloro-diphenyl-trichloroethane (DDT) causes impairment in male fertility in a cohort of DDT exposed workers, in Sardinia, Italy.

METHODS

We accessed official records on date of marriage and date of birth of the first child to estimate time to pregnancy (TTP) in the spouses of 1223 workers employed in a 1946-1950 anti-malarial campaign. The TTP calculation was censored at the 13th month after date of marriage. We used a modified Cox's proportional hazard model to calculate the fecundability ratio (FR) by job, by cumulative exposure to DDT, and by time window in relation to the anti-malarial operations, adjusting by paternal age at marriage.

RESULTS

Among the spouses of DDT applicators, fecundability did not vary during DDT use (FR=1.22, 95% CI 0.84-1.77) nor in the following decade (FR=1.01, 95% CI 0.67-1.50) with reference to the prior years. A significant increase occurred among the unexposed and the less exposed sub-cohorts, which generated a non-significantly reduced FR among the DDT applicator sub-cohort with reference to the unexposed following exposure.

CONCLUSION

We did not find evidence of an impairment in male fertility following heavy occupational exposure to DDT. However, although fecundability was highest among the spouses of the DDT applicators in the years prior to the anti-malarial campaign, we cannot exclude that DDT exposure prevented an increase parallel to that observed among the unexposed and the less exposed sub-cohorts.