The associations of particulate matters with fetal growth in utero and birth weight: A birth cohort study in Beijing, China

Association between ambient air pollution exposure and pregnancy outcomes in women treated with assisted reproductive technology: an updated systematic review and meta-analysis

BACKGROUND

Ambient air pollution has been recognized as a potential threat to reproductive system function. However, studies investigating the relationship between air pollutants and pregnancy outcomes, particularly in the context of assisted reproductive technology (ART), has yielded inconsistent findings.

METHODS

This study conducted an updated comprehensive search to identify observational studies published before October 14, 2023, that examined the associations between air pollution exposure and pregnancy outcomes among women undergoing ART. Meta-analysis using random effects models were employed to calculate pooled risk estimates of clinical pregnancy, biochemical pregnancy, and live birth.

RESULTS

A total of 20 studies were included in the systematic review and meta-analysis, with 12 studies included in the quantitative synthesis. The results revealed that exposure to carbon monoxide (CO) (RR = 0.949, 95% CI: 0.900, 0.999; I2 = 73%) and nitrogen dioxide (NO2) (RR = 0.976, 95% CI: 0.961, 0.992; I2 = 10%) during the period from ovarian stimulation to oocyte retrieval was associated with lower clinical pregnancy rates. Similarly, exposure to CO (RR = 0.985, 95% CI: 0.975, 0.996; I2 = 0%) and NO2 (RR = 0.978, 95% CI: 0.961, 0.996; I2 = 27%) during this period reduced biochemical pregnancy rates.

CONCLUSIONS

Our study highlights the potential association between air quality and ART outcomes, underscoring the need for improvements in air quality to enhance reproductive success.

The joint effects of prenatal exposure to PM2.5 constituents and reduced fetal growth on children's accelerated growth in the first 3 years: a birth cohort study

BACKGROUND

Prenatal fine particulate matter (PM2.5) constituents exposure and reduced fetal growth may be risk factors for accelerated growth in early childhood, an important indicator for lifelong health.

OBJECTIVE

The study investigated whether the joint effects are present between PM2.5 constituents and reduced fetal growth.

METHODS

The study was embedded in a birth cohort in China, including 5424 mother-child pairs. Prenatal PM2.5 and its constituents' [organic carbon (OC), elementary carbon (EC), ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-)] concentrations were estimated based on maternal residential addresses. Fetal growth was evaluated by fetal growth trajectory in utero and preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA). Children's accelerated growth was defined as body mass index (BMI) Z-score change of >0.67 between birth and 3 years. Generalized logistic regression was used to analyze the effects of prenatal PM2.5 constituents exposure and fetal growth on children's accelerated growth. Joint effect was tested on multiplicative scale and additive scale with the relative excess risk due to interaction (RERI).

RESULTS

Children with lower fetal growth trajectory, PTB, LBW, and SGA had increased odds of children's accelerated growth, with odds ratios (ORs) ranging from 1.704 to 11.605. Compared with lower exposure (≤median), higher exposure (>median) of PM2.5, OC, and SO42- were significantly associated with increased odds of children's accelerated growth, varying in ORs from 1.163 to 1.478. Prenatal exposure to OC had joint effects with lower fetal growth on children's accelerated growth. We observed that the interaction was statistically significant on an additive scale in OC and lower fetal growth trajectory (RERI: 0.497, 95% CI: 0.033,0.962).

IMPACT

Fine particulate matter (PM2.5) is a huge threat to human health worldwide, causing 6.7 million death globally in 2019. According to the theory of DOHaD, prenatal PM2.5 exposure could influence early childhood growth, which is important for lifelong health. We found that prenatal exposure to PM2.5, OC, and SO42- was associated with higher risk of accelerated childhood growth in the first 3 years. More importantly, reduced fetal growth moderated these associations. Our findings highlight the need for policies and interventions on PM2.5 constituents to improve lifelong health, especially for those vulnerable populations with reduced fetal growth.

Prenatal exposure to ambient air pollution and risk of fetal overgrowth: Systematic review of cohort studies

OBJECTIVES

Fetal overgrowth has detrimental effects on both the mother and the fetus. The global issue of ambient air pollution has been found to contribute to fetal overgrowth through various pathways. This study aimed to identify the association between prenatal exposure to ambient air pollution and the risk of fetal overgrowth.

METHODS

We identified articles between January 2013 and February 2024 by searching the Web of Sciences(WoS), PubMed, Proquest, Scopus, and Google Scholar databases. Quality assessment was performed using the Newcastle Ottawa scale. This review was provided based on the PRISMA guideline and registered with PROSPERO, "CRD42023488936".

RESULTS

The search generated 1719 studies, of which 22 cohort studies were included involving 3,480,041 participants. Results on the effects of air pollutants on fetal overgrowth are inconsistent because they vary in population and geographic region. But in general, the results indicate that prenatal exposure to air pollutants, specifically PM2.5, NO2, and SO2, is linked to a higher likelihood of fetal overgrowth(macrosomia and large for gestational age). Nevertheless, the relationship between CO and O3 pollution and fetal overgrowth remains uncertain. Furthermore, PM10 has a limited effect on fetal overgrowth. It is essential to consider the time that reproductive-age women are exposed to air pollution. Exposure to air pollutants before conception and throughout pregnancy has a substantial impact on the fetus's vulnerability to overgrowth.

CONCLUSIONS

Fetal overgrowth has implications for the health of both mother and fetus. fetal overgrowth can cause cardiovascular diseases, obesity, type 2 diabetes, and other diseases in adulthood, so it is considered an important issue for the health of the future generation. Contrary to popular belief that air pollution leads to intrauterine growth restriction and low birth weight, this study highlights that one of the adverse consequences of air pollution is macrosomia or LGA during pregnancy. Therefore governments must focus on implementing initiatives that aim to reduce pregnant women's exposure to ambient air pollution to ensure the health of future generations.

Gestational exposure to PM2.5 disrupts fetal development by suppressing placental trophoblast syncytialization via progranulin/mTOR signaling

Recent epidemiological and animal studies have indicated that ambient fine particulate matter (PM2.5) exposure during pregnancy is closely associated with intrauterine growth restriction (IUGR). However, the underlying mechanisms remain to be revealed. In this study, we found that gestational exposure to PM2.5 significantly decreased fetal weight and crown-rump length in mice, accompanied by insufficient placental trophoblast syncytialization and increased expression of progranulin (PGRN) in mice placenta. Administering PGRN neutralizing antibody to pregnant mice alleviated growth restriction and insufficient placental trophoblast syncytialization caused by PM2.5, accompanied with suppressed activation of the mTOR signaling pathway. Furthermore, in vitro experiments using human placental BeWo cells showed that 10 μg·mL-1 PM2.5 activated PGRN/mTOR signaling and suppressed forskolin-induced cell fusion, which was blocked by knockdown of PGRN. Taken together, our results demonstrated that PM2.5 exposure during pregnancy inhibited placental trophoblast syncytialization by activating PGRN/mTOR signaling, leading to abnormal placental development and IUGR. This study reveals a novel mechanism underlying the developmental toxicity of PM2.5 exposure during pregnancy.

The adverse impact of maternal ozone exposure on fetal growth in utero and the interaction with residential greenness

This study aimed to investigate the effect of maternal ozone exposure on fetal growth during pregnancy, as well as the combined effect and interaction of ozone and residential greenness. We included a total of 14990 singleton pregnancies from the Fujian Birth Cohort Study. During pregnancy, fetal growth parameters including estimated fetal weight (EFW), femur length (FL), head circumference (HC), and abdominal circumference (AC). To investigate the associations between ozone exposure and the above-mentioned outcomes, generalized estimating equation approach and generalized linear regression were used, as appropriate. In the adjusted models, we observed that the Z scores of EFW (-0.031 (-0.048, -0.014)), FL (-0.021 (-0.038, -0.004)), and AC (-0.025 (-0.042, -0.007)) decreased with per interquartile range (IQR) increase of ozone concentration. Compared to participants with low ozone exposure and high NDVI, those with high ozone exposure and low NDVI experienced the largest decrease in Z scores for EFW (-0.049 (-0.079, -0.02)), FL (-0.034 (-0.063, -0.004)), HC (-0.034 (-0.065, -0.004)), and AC (-0.041 (-0.072, -0.01)), respectively. Interestingly, we discovered the effect modification of NDVI on the relationship between ozone exposure and fetal growth restriction (P for interaction < 0.05). This study established a negative relationship of maternal ozone exposure and fetal growth. Of importance, this study discovered the joint effect and interaction between ozone and residential greenness exposure.

Prenatal ambient air pollution exposure and child weight trajectories from the 3rd trimester of pregnancy to 2 years of age: a cohort study

BACKGROUND

Prenatal air pollution exposure may increase risk for childhood obesity. However, few studies have evaluated in utero growth measures and infant weight trajectories. This study will evaluate the associations of prenatal exposure to ambient air pollutants with weight trajectories from the 3rd trimester through age 2 years.

METHODS

We studied 490 pregnant women who were recruited from the Maternal and Development Risks from Environmental and Social Stressors (MADRES) cohort, which comprises a low-income, primarily Hispanic population in Los Angeles, California. Nitrogen dioxide (NO2), particulate matter < 10 µm (PM10), particulate matter < 2.5 µm (PM2.5), and ozone (O3) concentrations during pregnancy were estimated from regulatory air monitoring stations. Fetal weight was estimated from maternal ultrasound records. Infant/child weight measurements were extracted from medical records or measured during follow-up visits. Piecewise spline models were used to assess the effect of air pollutants on weight, overall growth, and growth during each period.

RESULTS

The mean (SD) prenatal exposure concentrations for NO2, PM2.5, PM10, and O3 were 16.4 (2.9) ppb, 12.0 (1.1) μg/m3, 28.5 (4.7) μg/m3, and 26.2 (2.9) ppb, respectively. Comparing an increase in prenatal average air pollutants from the 10th to the 90th percentile, the growth rate from the 3rd trimester to age 3 months was significantly increased (1.55% [95%CI 1.20%, 1.99%] for PM2.5 and 1.64% [95%CI 1.27%, 2.13%] for NO2), the growth rate from age 6 months to age 2 years was significantly decreased (0.90% [95%CI 0.82%, 1.00%] for NO2), and the attained weight at age 2 years was significantly lower (- 7.50% [95% CI - 13.57%, - 1.02%] for PM10 and - 7.00% [95% CI - 11.86%, - 1.88%] for NO2).

CONCLUSIONS

Prenatal ambient air pollution was associated with variable changes in growth rate and attained weight from the 3rd trimester to age 2 years. These results suggest continued public health benefits of reducing ambient air pollution levels, particularly in marginalized populations.

Philadelphia Towards Racial and Environmental Equity (Philly TREEs): how a medical school can advance health equity through urban forestry in Philadelphia, PA, USA

Inequity in access to urban greenspaces might contribute to health disparities in the USA via multiple pathways. Academic medical centres can promote health equity in their surrounding communities by partnering with community organisations to improve greenspace access in urban environments. Academic medical centres are also uniquely positioned to advance health-equity leadership among the next generation of doctors through medical-education initiatives; of particular importance is that medical professionals are involved in advocating for the expansion of greenspace access due to its direct relationship with human health and wellness. Furthermore, by focusing educational, research, and service endeavours on addressing the most important health issues within their communities, institutions could allocate some of their resources towards community greening as a form of preventive health investment. This Personal View describes our medical-student-led pilot project Philadelphia Towards Racial and Environmental Equity (Philly TREEs) at the Perelman School of Medicine (University of Pennsylvania, Philadelphia, PA, USA), which aims to improve tree equity and community wellness in Philadelphia. We highlight this project to show how academic medical institutions can help cities to achieve urban tree-canopy goals in an equitable way through community partnership and address disparities in the environment and in health.

Prenatal exposure to PM2.5 and its constituents with children's BMI Z-score in the first three years: A birth cohort study

BACKGROUND

Limited studies evaluated the effect of prenatal exposure to fine particulate matter (PM2.5) on childhood growth and no consensus reached yet. No study explored the effect of prenatal exposure to PM2.5 and its constituents on childhood growth in a region with high PM2.5 levels (>50 μg/m3). The present study aimed to examine the association of prenatal exposure to PM2.5 and its constituents with children's BMI Z-score in the first three years.

METHODS

The present study was based on a birth cohort in Beijing, China, involving 15,745 mothers with their children who were followed to three years old. We estimated prenatal PM2.5 and its constituents [organic carbon (OC), elemental carbon (EC), sulfate (SO42-), nitrate (NO3-), and ammonium (NH4+)] concentrations based on residential addresses at birth. Height (or length) and weight of children were repeatedly measured, and body mass index (BMI) Z-score was calculated at one, two, and three years old. Generalized linear regression and generalized estimating equation were used to examine the associations between prenatal exposure to PM2.5 and its constituents with BMI Z-score in the first three years.

RESULTS

Prenatal exposure to PM2.5 and its constituents was generally associated with higher BMI Z-score of children aged one, two, and three years. One IQR increase of PM2.5, OC, EC, NO3-, NH4+, and SO42- (21.30 μg/m3, 11.52 μg/m3, 2.40 μg/m3, 8.28 μg/m3, 2.42 μg/m3, and 8.80 μg/m3, respectively) was associated with 0.13 (95%CI: 0.10, 0.16), 0.24 (95%CI: 0.19, 0.29), 0.12 (95%CI: 0.09, 0.16), 0.13 (95%CI: 0.09, 0.17), 0.11 (95%CI: 0.08, 0.13), and 0.24 (95%CI: 0.19, 0.30) increase in BMI Z-score from one to three years old, respectively.

CONCLUSION

The study suggested that prenatal exposure to PM2.5 and its constituents was associated with higher BMI Z-score of children in the first three years. Public health policy for controlling harmful PM2.5 constituents should be developed to promote child health.

Individual and joint effect of indoor air pollution index and ambient particulate matter on fetal growth: a prospective cohort study

BACKGROUND

Limited studies have examined the effect of prenatal exposure to particulate matter with diameter of <2.5 µm (PM2.5) and <1 μm (PM1) on fetal growth using ultrasound measurements with inconsistent results. No study has evaluated the joint effect of the indoor air pollution index and ambient particulate matter on fetal growth.

METHODS

We conducted a prospective birth cohort study in Beijing, China in 2018, including 4319 pregnant women. We estimated prenatal PM2.5 and PM1 exposure using a machine-learning method and calculated the indoor air pollution index based on individual interviews. Gender- and gestational age-adjusted Z-score of the abdominal circumference (AC), head circumference (HC), femur length (FL) and estimated fetal weight (EFW) was calculated and then undergrowth was defined. A generalized estimating equation was used to evaluate the individual and joint effect of indoor air pollution index, PM2.5 and PM1 on fetal Z-score and undergrowth parameters.

RESULTS

One unit increase in the indoor air pollution index was associated with -0.044 (95% CI: -0.087, -0.001) and -0.050 (95% CI: -0.094, -0.006) decrease in the AC and HC Z-scores, respectively. PM1 and PM2.5 were associated with decreased AC, HC, FL and EFW Z-scores, and higher risk of undergrowth. Compared with exposure to lower PM1 (≤ median) and no indoor air pollution, those exposed to higher PM1 (> median) and indoor air pollution had decreased EFW Z-scores (β = -0.152, 95% CI: -0.230, -0.073) and higher risk of EFW undergrowth (RR = 1.651, 95% CI: 1.106, 2.464). Indoor air pollution and ambient PM2.5 exposure had a similar joint effect on the Z-scores and undergrowth parameters of fetal growth.

CONCLUSIONS

This study suggested that indoor air pollution and ambient PM exposure had individual and joint negative effects on fetal growth.

Effect of levothyroxine treatment on fetal growth among women with mild subclinical hypothyroidism and thyroid peroxidase antibody negative: a cohort study

BACKGROUND

Some clinicians used levothyroxine (LT4) treatment for mild subclinical hypothyroidism (SCH) pregnant women (2.5 < thyroid-stimulating hormone (TSH) ≤ the pregnancy-specific reference range with normal free thyroxine (FT4) level) with thyroid peroxidase antibody negative (TPOAb^-), although the recent clinical guideline did not recommend it. It is unknown whether LT4 treatment for pregnant women with mild SCH and TPOAb^- have impact on fetal growth. Therefore, the aim of the study was to investigate the effect of LT4 treatment on fetal growth and birth weight among mild SCH pregnant women with TPOAb^-.

METHODS

This was a birth cohort study including 14,609 pregnant women between 2016 and 2019 in Tongzhou Maternal and Child Health Hospital of Beijing, China. Pregnant women were divided into 3 groups as follows: Euthyroid (n = 14,285, 0.03 ≤ TSH ≤ 2.5mIU/L, normal FT4), TPOAb^-; Untreated mild SCH with TPOAb^- (n = 248, 2.5 < TSH ≤ 2.9mIU/L, normal FT4, without LT4 treatment); Treated mild SCH with TPOAb^- (n = 76, 2.5 < TSH ≤ 2.9mIU/L, normal FT4, with LT4 treatment). The main outcome measures were Z-scores of fetal growth indicators (abdominal circumference (AC), biparietal diameter (BPD), femur length (FL), head circumference (HC), estimated fetal weight (EFW)), fetal growth restriction (FGR) and birth weight.

RESULTS

There was no difference in fetal growth indicators and birth weight between the untreated mild SCH women with TPOAb^- and the euthyroid pregnant women. But the HC Z-score was lower in the LT4 treated mild SCH women with TPOAb^-, compared with the euthyroid pregnant women (β = -0.223, 95%CI: -0.422, -0.023). The LT4 treated mild SCH women with TPOAb^- had lower fetal HC Z-score (β = -0.236, 95%CI: -0.457, -0.015), compared with the untreated mild SCH women with TPOAb^-.

CONCLUSIONS

We observed that LT4 treatment for mild SCH with TPOAb^- was associated with decreased fetal HC, which was not observed for untreated mild SCH women with TPOAb^-. The adverse effect of LT4 treatment for mild SCH with TPOAb^- provided new evidence for the recent clinical guideline.

Association of air pollution exposure during gestational and the first year of life with physical growth in preschoolers

This study explored the association of exposure to air pollutants during gestational and the first year of life with physical growth in preschoolers. The linear and logistic regression models were used to estimate the associations between air pollution and childhood growth. After adjusting for confounders, z-scores of body mass index (zBMI, and 95% confidence intervals, 95%CI) increased by 1.164(1.054,1.285), 1.136(1.050,1.228) and 1.165(1.041,1.303), associated with per interquartile range (IQR) increase in NO₂ (nitrogen dioxide), PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters ≤2.5 μm and 10 μm) during gestational, respectively. The odds ratios (and 95%CI) of childhood overweight/obesity associated with per IQR increase in NO₂, PM_2.5 and PM₁₀ during gestational were 1.425(1.168,1.737), 1.255(1.087,1.450) and 1.332(1.104,1.605). Positive associations were found between air pollution during the first year of life and zBMI or overweight/obesity. Our findings suggest exposure to air pollution were associated with childhood growth, and improving air quality is beneficial for childhood growth.

The effect of exposure to traffic related air pollutants in pregnancy on birth anthropometry: a cohort study in a heavily polluted low-middle income country

BACKGROUND

Ambient air pollution has been recognized as one of the most important environmental health threats. Exposure in early life may affect pregnancy outcomes and the health of the offspring. The main objective of our study was to assess the association between prenatal exposure to traffic related air pollutants during pregnancy on birth weight and length. Second, to evaluate the association between prenatal exposure to traffic related air pollutants and the risk of low birth weight (LBW).

METHODS

Three hundred forty mother-infant pairs were included in this prospective cohort study performed in Jakarta, March 2016-September 2020. Exposure to outdoor PM_2.5, soot, NO_x, and NO₂ was assessed by land use regression (LUR) models at individual level. Multiple linear regression models were built to evaluate the association between air pollutants with birth weight (BW) and birth length (BL). Logistic regression was used to assess the risk of low birth weight (LBW) associated with all air pollutants.

RESULTS

The average PM_2.5 concentration was almost eight times higher than the current WHO guideline and the NO₂ level was three times higher. Soot and NO_x were significantly associated with reduced birth length. Birth length was reduced by - 3.83 mm (95% CI -6.91; - 0.75) for every IQR (0.74 × 10^- 5 per m) increase of soot, and reduced by - 2.82 mm (95% CI -5.33;-0.30) for every IQR (4.68 μg/m³) increase of NO_x. Outdoor air pollutants were not significantly associated with reduced birth weight nor the risk of LBW.

CONCLUSION

Exposure to soot and NO_x during pregnancy was associated with reduced birth length. Associations between exposure to all air pollutants with birth weight and the risk of LBW were less convincing.

Maternal atmospheric particulate matter exposure and risk of adverse pregnancy outcomes: A meta-analysis of cohort studies

Ambient air particulate exposure not only capable of elevating the risks of adverse pregnancy outcomes, but also has profound implications for human health, but the results are discrepant. This meta-analysis aimed to provide higher grade evidence on the impacts of air particulate on specific pregnancy outcomes. A total of 81 eligible cohort studies were included in this meta-analysis, of which the outcomes included preterm birth (PTB), moderate PTB, very PTB, extreme PTB, term low birth weight (TLBW), term birth weight (TBW), stillbirth (SB) and small for gestational age (SGA). The results showed that every 10 μg/m³ increase of PM_2.5 exposure associated with 2.7%-9.3% increase of PTB risk in entire pregnancy, 2nd and 3rd trimesters; 10.5%-19.3% increase of very PTB risk in entire pregnancy, 1st and 2nd trimesters; 8.3% and 10.1% increase of TLBW and SGA risk in entire pregnancy; 25.6% and 10.1% increase of SB in entire pregnancy and 3rd trimester; and -13.274 g and -4.916 g reduce of TBW during entire pregnancy and 2nd trimester, respectively. Every 10 μg/m³ increase of PM₁₀ exposure associated with 12.1% and 2.6% increase of PTB risk in entire pregnancy and 3rd trimester; 48.9% and 5.0% increase of moderate PTB risk in entire pregnancy and 2nd trimester; 14.4% and 10.3% increase of very PTB risk in 1st and 3rd trimesters; 2.9% increase of extremely PTB risk in 2nd trimester; 1.5%-3.8% and 2.9%-3.7% increase of TLBW and SGA risk in entire pregnancy, 1st and 2nd trimesters; 7.0% increase of SB risk in 3rd trimesters; and -4.537 g and -5.263 g reduce of TBW in 1st and 2nd trimesters, respectively. High mean annual PM concentrations were associated with more extreme adverse pregnancy outcomes (PTBs, SGA and SB), while low mean annual PM concentrations were associated with decreased TBW and increased risk of TLBW.

Susceptible windows of exposure to fine particulate matter and fetal growth trajectories in the Spanish INMA (INfancia y Medio Ambiente) birth cohort

While prior studies report associations between fine particulate matter (PM2.5) exposure and fetal growth, few have explored temporally refined susceptible windows of exposure. We included 2328 women from the Spanish INMA Project from 2003 to 2008. Longitudinal growth curves were constructed for each fetus using ultrasounds from 12, 20, and 34 gestational weeks. Z-scores representing growth trajectories of biparietal diameter, femur length, abdominal circumference (AC), and estimated fetal weight (EFW) during early (0-12 weeks), mid- (12-20 weeks), and late (20-34 weeks) pregnancy were calculated. A spatio-temporal random forest model with back-extrapolation provided weekly PM2.5 exposure estimates for each woman during her pregnancy. Distributed lag non-linear models were implemented within the Bayesian hierarchical framework to identify susceptible windows of exposure for each outcome and cumulative effects [βcum, 95% credible interval (CrI)] were aggregated across adjacent weeks. For comparison, general linear models evaluated associations between PM2.5 averaged across multi-week periods (i.e., weeks 1-11, 12-19, and 20-33) and fetal growth, mutually adjusted for exposure during each period. Results are presented as %change in z-scores per 5 μg/m3 in PM2.5, adjusted for covariates. Weeks 1-6 [βcum = -0.77%, 95%CrI (-1.07%, -0.47%)] were identified as a susceptible window of exposure for reduced late pregnancy EFW while weeks 29-33 were positively associated with this outcome [βcum = 0.42%, 95%CrI (0.20%, 0.64%)]. A similar pattern was observed for AC in late pregnancy. In linear regression models, PM2.5 exposure averaged across weeks 1-11 was associated with reduced late pregnancy EFW and AC; but, positive associations between PM2.5 and EFW or AC trajectories in late pregnancy were not observed. PM2.5 exposures during specific weeks may affect fetal growth differentially across pregnancy and such associations may be missed by averaging exposure across multi-week periods, highlighting the importance of temporally refined exposure estimates when studying the associations of air pollution with fetal growth.

Identifying pre-conception and pre-natal periods in which ambient air pollution exposure affects fetal growth in the predominately Hispanic MADRES cohort

BACKGROUND

It is well documented that persons of color experience disproportionate exposure to environmental contaminants, including air pollution, and have poorer pregnancy outcomes. This study assessed the critical windows of exposure to ambient air pollution on in utero fetal growth among structurally marginalized populations in urban Los Angeles.

METHODS

Participants (N = 281) from the larger ongoing MADRES pregnancy cohort study were included in this analysis. Fetal growth outcomes were measured on average at 32 [Formula: see text] 2 weeks of gestation by a certified sonographer and included estimated fetal weight, abdominal circumference, head circumference, biparietal diameter and femur length. Daily ambient air pollutant concentrations were estimated for four pollutants (particulate matter less than 2.5 µm (PM_2.5) and less than 10 µm (PM₁₀) in aerodynamic diameter, nitrogen dioxide (NO₂), and 8-h maximum ozone (O₃)) at participant residences using inverse-distance squared spatial interpolation from ambient monitoring data. Weekly gestational averages were calculated from 12 weeks prior to conception to 32 weeks of gestation (44 total weeks), and their associations with growth outcomes were modeled using adjusted distributed lag models (DLMs).

RESULTS

Participants were on average 29 years [Formula: see text] 6 old and predominately Hispanic (82%). We identified a significant sensitive window of PM_2.5 exposure (per IQR increase of 6 [Formula: see text]³) between gestational weeks 4-16 for lower estimated fetal weight [Formula: see text] _averaged4-16 = -8.7 g; 95% CI -16.7, -0.8). Exposure to PM_2.5 during gestational weeks 1-23 was also significantly associated with smaller fetal abdominal circumference ([Formula: see text] _averaged1-23 = -0.6 mm; 95% CI -1.1, -0.2). Additionally, prenatal exposure to PM₁₀ (per IQR increase of 13 [Formula: see text]³) between weeks 6-15 of pregnancy was significantly associated with smaller fetal abdominal circumference ([Formula: see text] _{averaged6-15 =} -0.4 mm; 95% CI -0.8, -0.1).

DISCUSSION

These results suggest that exposure to particulate matter in early to mid-pregnancy, but not preconception or late pregnancy, may have critical implications on fetal growth.

Overview of particulate air pollution and human health in China: Evidence, challenges, and opportunities

Ambient particulate matter (PM) pollution in China continues to be a major public health challenge. With the release of the new WHO air quality guidelines in 2021, there is an urgent need for China to contemplate a revision of air quality standards (AQS). In the recent decade, there has been an increase in epidemiological studies on PM in China. A comprehensive evaluation of such epidemiological evidence among the Chinese population is central for revision of the AQS in China and in other developing countries with similar air pollution problems. We thus conducted a systematic review on the epidemiological literature of PM published in the recent decade. In summary, we identified the following: (1) short-term and long-term PM exposure increase mortality and morbidity risk without a discernible threshold, suggesting the necessity for continuous improvement in air quality; (2) the magnitude of long-term associations with mortality observed in China are comparable with those in developed countries, whereas the magnitude of short-term associations are appreciably smaller; (3) governmental clean air policies and personalized mitigation measures are potentially effective in protecting public and individual health, but need to be validated using mortality or morbidity outcomes; (4) particles of smaller size range and those originating from fossil fuel combustion appear to show larger relative health risks; and (5) molecular epidemiological studies provide evidence for the biological plausibility and mechanisms underlying the hazardous effects of PM. This updated review may serve as an epidemiological basis for China’s AQS revision and proposes several perspectives in designing future health studies.

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Acute effects of PM are smaller in China compared with developed countries

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Health effects caused by PM depend on particle composition, source, and size

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There are no thresholds for the health effects of PM

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Mechanistic studies support the biological plausibility of PM’s health effects

The associations of prenatal exposure to PM2.5 and its constituents with fetal growth: A prospective birth cohort in Beijing, China

BACKGROUND

Limited studies investigated the association of prenatal exposure to PM2.5 and fetal growth measured by ultrasound with inconsistent results. No study evaluated the effect of PM2.5 constituents on fetal growth in utero. We aimed to investigated whether prenatal exposure to PM2.5 and its constituents was associated with fetal growth measured by ultrasound.

METHODS

A total of 4319 eligible pregnant women in Peking University Birth Cohort in Tongzhou (PKUBC-T) were included in the study. Based on mothers' residential addresses, we estimated prenatal PM2.5 concentrations with a satellite-based spatiotemporal model and PM2.5 constituents concentrations with a modified Community Multiscale Air Quality model. Fetal growth parameters of abdominal circumference (AC), head circumference (HC), and femur length (FL) were measured by ultrasound and then estimated fetal weight (EFW) was calculated. We calculated sex and gestational age-specific fetal growth Z-score and then defined the corresponding fetal undergrowth. Generalized estimating equation was used to investigate the association of PM2.5 and its constituents with fetal growth Z-score and fetal undergrowth.

RESULTS

Prenatal exposure to PM2.5, OC, EC, SO42-, NH4+, or NO3- was consistently associated with decreased Z-scores of fetal growth parameters (AC, HC, FL, EFW). One IQR increase of PM2.5, OC, EC, SO42-, NH4+, or NO3- was associated with -0.183 [95% confident interval (CI): -0.225, -0.141], -0.144 (95%CI: -0.181, -0.107), -0.123 (95%CI: -0.160, -0.085), -0.035 (95%CI: -0.055, -0.015), -0.095 (95%CI: -0.126, -0.064), and -0.124 (95%CI: -0.159, -0.088) decrease in EFW Z-score, respectively. Prenatal exposure to PM2.5, OC, EC, SO42-, NH4+, or NO3- was also associated with higher risk of fetal AC, HC, FL or EFW undergrowth.

CONCLUSION

The study identified that prenatal exposure to PM2.5 or its constituents was associated with impaired fetal growth. The findings provided evidence that control measures for PM2.5 constituents should be implemented for further promoting fetal growth.

Early pregnancy PM2.5 exposure and its inorganic constituents affect fetal growth by interrupting maternal thyroid function

Early pregnancy is crucial for fetal growth. Maternal thyroid hormone is critical for fetal growth and can be disturbed under exogenous exposure. However, it's uncertain whether exposure to PM_2.5 and inorganic constituents during early pregnancy can affect TH and fetal growth. We focused on the associations of early-pregnancy PM_2.5 and inorganic constituents with fetal growth and maternal THs. PM_2.5 concentration was estimated using a satellite-based spatiotemporal model. Fetal biparietal diameter (BPD), head circumference (HC), femur length (FL), and humerus length (HL) were measured by ultrasonography at median 15.6, 22.2, and 33.1 gestational weeks. Levels of 28 PM_2.5 constituents were measured in a sub-group of 329 pregnancies. Maternal serum free thyroxine (fT4), free triiodothyronine, and thyroid-stimulating hormone levels were measured at 14 weeks of gestation. Mixed-effect models and multiple linear regression were applied to evaluate the associations of PM_2.5 and its constituents with fetal growth measures. Mediation analysis was used to examine the mediating role of the THs. Results showed that each 10 μg/m³ increase in PM_2.5 was associated with 0.20 mm reductions in BPD (95%CI: 0.33, -0.01), 0.27 mm decreases in FL (95%CI: 0.40, -0.13), and 0.36 decreases in HL (95%CI: 0.49, -0.23). Per 10 μg/m³ increment in PM_2.5 was correlated with 5.82% decreases in the fT4 level (95% CI: 8.61%, -2.96%). FT4 accounted for 14.3% of PM_2.5 exposure-induced change in BPD at first follow-up. Al (β = -2.91, 95%CI: 5.17, -0.66), Si (β = -1.20, 95%CI: 2.22, -0.19), K (β = -3.09, 95%CI: 5.41, -0.77), Mn (β = -47.20, 95%CI: 83.68, -10.79) and Zn (β = -3.02, 95%CI: 5.55, -0.49) were associated with decreased fetal BPD, especially in first follow-up. Zn (β = -38.12%, 95% CI: 58.52%, -8.61%) was also associated with decreased fT4 levels. Overall, early pregnancy exposure to PM_2.5 and its constituents was associated with fetal growth restriction and decreased maternal fT4 levels might mediate the effect of PM_2.5.

Health Outcomes in Children Associated with Prenatal and Early-Life Exposures to Air Pollution: A Narrative Review

(1) Background: The developmental origins of health and disease (DOHaD) hypothesis links adverse fetal exposures with developmental mal-adaptations and morbidity later in life. Short- and long-term exposures to air pollutants are known contributors to health outcomes; however, the potential for developmental health effects of air pollution exposures during gestation or early-childhood have yet to be reviewed and synthesized from a DOHaD lens. The objective of this study is to summarize the literature on cardiovascular and metabolic, respiratory, allergic, and neuropsychological health outcomes, from prenatal development through early childhood, associated with early-life exposures to outdoor air pollutants, including traffic-related and wildfire-generated air pollutants. (2) Methods: We conducted a search using PubMed and the references of articles previously known to the authors. We selected papers that investigated health outcomes during fetal or childhood development in association with early-life ambient or source-specific air pollution exposure. (3) Results: The current literature reports that prenatal and early-childhood exposures to ambient and traffic-related air pollutants are associated with a range of adverse outcomes in early life, including cardiovascular and metabolic, respiratory and allergic, and neurodevelopmental outcomes. Very few studies have investigated associations between wildfire-related air pollution exposure and health outcomes during prenatal, postnatal, or childhood development. (4) Conclusion: Evidence from January 2000 to January 2022 supports a role for prenatal and early-childhood air pollution exposures adversely affecting health outcomes during development. Future studies are needed to identify both detrimental air pollutants from the exposure mixture and critical exposure time periods, investigate emerging exposure sources such as wildfire, and develop feasible interventional tools.

Associations among prenatal PM2.5, birth weight, and renal function

BACKGROUND

Low birth weight has long-term health effects, including neurodevelopmental delays, cardiovascular diseases, and type 2 diabetes, through epigenetic changes and modifications. Numerous studies have identified that PM2.5 is associated with low birth weight. However, the association between PM2.5 and renal function, as well as the mediated effect of renal function on the association between prenatal PM2.5 and birth weight are still under-recognized.

METHODS

A total of 8969 singleton live births born in 2015-2019 were included in this study. The inverse distance weighting method was applied to interpolate and calculate the average exposure to PM2.5 during pregnancy for each pregnant woman. The multiple linear regression model was used to shed light on the associations among prenatal PM2.5, birth weight, and renal function. In addition, the mediation analysis was performed to figure out the mediated effect of renal function on the association between prenatal PM2.5 and birth weight, and the proportion of mediated effect = (indirect effect/total effect) × 100%.

RESULTS

Per 10 μg/m3 increment of prenatal PM2.5 was associated with 8.98 g (95% CI: -16.94 to -1.02) decrease of birth weight, 0.49 (95% CI: -0.73 to -0.26) ml/min/1.73 m2 decrease of glomerular filtration rate (GFR), 0.03 (95% CI: 0.01-0.05) mmol/L increase of blood urea nitrogen (BUN), and 2.29 (95% CI: 0.86-3.72) μmol/L increase of uric acid (UA) after adjusting for the sociodemographic covariates, disease-related covariates and meteorological factors. Besides, the mediated effects of GFR and BUN on the association between prenatal PM2.5 and birth weight were 5.02% and 14.96%, but there was no significant mediated effect being identified in UA.

CONCLUSION

Prenatal PM2.5 is related to reduced birth weight and impaired renal function. Renal function plays a partial role in the association between prenatal PM2.5 and birth weight. Appropriate guidelines should be formulated by the concerned authorities, and adequate efforts should be made to mitigate the detrimental health effects of PM2.5.

Associations of Ambient Fine Particulate Matter and Its Chemical Constituents with Birth Weight for Gestational Age in China: A Nationwide Survey

This study examined the associations of fine particulate matter (PM_2.5) and its chemical constituents with risks of small for gestational age (SGA) and large for gestational age (LGA). Based on the China Labor and Delivery Survey, we included 70,206 birth records from 24 provinces in China. Concentrations of PM_2.5 mass and six main constituents were estimated using satellite-based models. Logistic regression analysis was used to examine the associations, adjusted for sociodemographic characteristics and time trends. We found that an interquartile range increase in PM_2.5 exposure during pregnancy was associated with 16% (95% confidence interval [CI]: 3-30%) and 11% (95% CI: 1-22%) higher risk of SGA and LGA, respectively. Elevated risk of SGA was associated with exposure to black carbon [odds ratio (OR) = 1.15, 95% CI: 1.00-1.32], ammonium (OR = 1.12, 95% CI: 1.01-1.25), and sulfate (OR = 1.12, 95% CI: 1.04-1.21); while increased risk of LGA was associated with exposure to black carbon (OR = 1.13, 95% CI: 1.02-1.26), ammonium (OR = 1.13, 95% CI: 1.03-1.24), sulfate (OR = 1.08, 95% CI: 1.01-1.15), and nitrate (OR = 1.14, 95% CI: 1.03-1.27). Our findings provide evidence that PM_2.5 exposure was associated with increased risks of SGA and LGA, and constituents related to emissions from anthropogenic sources may play important roles in these associations.

Identifying Sensitive Windows of Exposure to NO2 and Fetal Growth Trajectories in a Spanish Birth Cohort

BACKGROUND

We previously identified associations between trimester-specific NO2 exposures and reduced fetal growth in the Spanish INfancia y Medio Ambiente (INMA) project. Here, we use temporally refined exposure estimates to explore the impact of narrow (weekly) windows of exposure on fetal growth.

METHODS

We included 1,685 women from INMA with serial ultrasounds at 12, 20, and 34 gestational weeks. We measured biparietal diameter (BPD), femur length, and abdominal circumference (AC) and from them calculated estimated fetal weight (EFW). We calculated z-scores describing trajectories of each parameter during early (0-12 weeks), mid (12-20 weeks), and late (20-34 weeks) pregnancy, based on longitudinal growth curves from mixed-effects models. We estimated weekly NO2 exposures at each woman's residence using land-use regression models. We applied distributed lag nonlinear models to identify sensitive windows of exposure. We present effect estimates as the percentage change in fetal growth per 10 μg/m3 increase in NO2 exposure, and we calculated cumulative effect estimates by aggregating estimates across adjacent lags.

RESULTS

We identified weeks 5-12 as a sensitive window for NO2 exposure on late EFW (cumulative β = -3.0%; 95% CI = -4.1%, -1.9%). We identified weeks 6-19 as a sensitive window for late growth in BPD (cumulative β = -2.0%; 95% CI = -2.7%, -1.4%) and weeks 8-13 for AC (cumulative β = -0.68%; 95% CI = -0.97%, -0.40%). We found suggestive evidence that third trimester NO2 exposure is associated with increased AC, BPD, and EFW growth in late pregnancy.

CONCLUSIONS

Our findings are consistent with the hypothesis that NO2 exposure is associated with alterations in growth of EFW, BPD, and AC dependent on the specific timing of exposure during gestation.

Prenatal exposure to air pollution and the risk of macrosomia: Identifying windows of susceptibility

This study explores the effects of prenatal exposure to air pollution on the risk of macrosomia and its window of susceptibility. We conducted a retrospective cohort study utilizing records of birth certificates for all full-term live newborns born in Xi'an city, China from January 1, 2015, to December 31, 2018.Weekly- and trimester-specific exposures of PM2.5, PM10, NO2, and O3 during pregnancy were calculated by inverse distance weighting (IDW) based on their residences. Cox proportional hazard model and distributed lag models (DLMs) were performed to estimate the effects of air pollution exposure during pregnancy on macrosomia risk and its window of susceptibility. In total, 318,323 full-term newborns were identified, including 24,996 (7.8%) cases of macrosomia. An IQR increase in PM2.5 exposure (45.46 μg/m3) from the 33rd until the 37th weeks of gestation was positively associated with an elevated risk of macrosomia, with the strongest effect in the 37th weeks (HR = 1.007, 95%CI: 1.002-1.013). The window of susceptibility for NO2 exposure on macrosomia risk was in the 29th-35th gestational weeks, with the strongest effect in the 34th weeks (IQR = 21.96 μg/m3, HR = 1.006, 95%CI:1.000-1.013). For prenatal exposure to O3, 5th-24th weeks of gestation was identified as susceptible windows for elevated risk of macrosomia, with the strongest associations observed in the 15th weeks (IQR = 80.53 μg/m3, HR = 1.022, 95%CI: 1.011-1.033). However, we did not observe any associations between weekly exposure of PM10 and macrosomia. Our findings imply that the windows of susceptibility to PM2.5 and NO2 exposure on macrosomia are mainly in late pregnancy, whereas the windows of susceptibility to O3 exposure are in early and middle pregnancy.

Individual and joint effects of prenatal green spaces, PM2.5 and PM1 exposure on BMI Z-score of children aged two years: A birth cohort study

BACKGROUND

Few studies examined the association of prenatal exposure to green spaces with children's body mass index (BMI) Z-score, and no study evaluated the joint effect of prenatal green spaces and PM_2.5 or PM₁ exposure on children's BMI Z-score. We aimed to assess the individual and joint effects of prenatal green spaces, PM_2.5, and PM₁ exposure on BMI Z-score of children aged two years.

METHODS

The study was based on a birth cohort in Beijing, China, in which 13,253 mothers (LMP from 2014 to 2017) and their children were included. We estimated prenatal green spaces exposure by calculating average normalized difference vegetation index with 500 m buffers (NDVI-500), prenatal PM_2.5 and PM₁ exposure based on maternal residential addresses. Weight and height of children were measured at 2 years old. We calculated children's BMI Z-score based on the WHO Standards. Generalized linear regression was used to examine the individual and joint effects of prenatal NDVI-500, PM_2.5 and PM₁ exposure on children's BMI Z-score.

RESULTS

A 0.1 increase in prenatal NDVI-500 exposure, a 10 μg/m³ decrease in PM_2.5, a 10 μg/m³ decrease in PM₁ were associated with 0.185 [95% confidence interval (95%CI): 0.155, 0.216], 0.034 (95%CI: 0.015, 0.052) and 0.041 (95%CI: 0.020, 0.061) increase of children's BMI Z-score, respectively. Compared with those exposed to low-level NDVI-500 (not greater than median) and high-level PM_2.5 (greater than median), the BMI Z-score was higher in children whose mother exposed to high-level of NDVI-500 and low-level PM_2.5 [β:0.172 (95%CI: 0.131, 0.214), P_interaction = 0.003]. Compared with those exposed to low-level NDVI-500 and high-level PM₁, the BMI Z-score was higher in children whose mother exposed to high-level of NDVI-500 and low-level PM₁ [β:0.169 (95%CI: 0.127, 0.210), P_interaction<0.001]. In the trimester-specific analysis, NDVI-500 and PM exposure during the second trimester have a consistent individual effect, together with a joint effect, on child growth.

CONCLUSION

The study suggested the beneficial effect of prenatal exposure to green spaces on child growth and its interaction with PM_2.5 and PM₁, especially in the second trimester. The findings call for developing public health policy to improve green infrastructure and control PM_2.5 and PM₁ concentrations, in order to promote child growth.

The association between biomass fuel use for cooking and linear growth in young children in Bhaktapur, Nepal

BACKGROUND

There are still many people in the world who prepare their meals on open fires or stoves using solid fuels from biomass, especially in low-and middle-income countries. Although biomass cooking fuels have been associated with adverse health impacts and diseases, the association with child linear growth remains unclear.

OBJECTIVES

In a cohort design, we aimed to describe the association between the use of biomass cooking fuels and linear growth in children aged 18-23 months living in the urban and peri-urban community of Bhaktapur, situated in the Kathmandu valley in Nepal.

METHODS

Caretakers of 600 marginally stunted children aged 6-11 months were interviewed about their source of cooking fuel and other socio-demographic characteristics at enrolment into a randomized controlled trial. Children's body length was measured when children were 18-23 months old. In linear regression models, we estimated the association between the use of biomass fuel and length-for-age Z-scores (LAZ), adjusted for relevant confounders. We repeated these analyses in pre-defined sub-groups and different percentiles of LAZ using quantile regression models.

RESULTS

Among study participants, 101 (18%) used biomass as cooking fuel. The association between biomass fuel and LAZ was not statistically significant in the full sample (adjusted regression coefficient: -0.14, 95% CI: -0.28, 0.00). The association was stronger in some of the sub-groups and in the lower tail of the LAZ distribution (those who are stunted), but neither reached statistical significance.

DISCUSSION

Children from households in poor, urban neighborhoods in Nepal which used biomass fuel for cooking were on average slightly shorter than other children, although the association only approached statistical significance. As this was an observational study, residual confounding cannot be excluded. Further studies are needed to confirm these associations, in particular those seen in certain sub-groups.

Maternal exposure to ambient PM2.5 and term birth weight: A systematic review and meta-analysis of effect estimates

Effect estimates of prenatal exposure to ambient PM_2.5 on change in grams (β) of birth weight among term births (≥37 weeks of gestation; term birth weight, TBW) vary widely across studies. We present the first systematic review and meta-analysis of evidence regarding these associations. Sixty-two studies met the eligibility criteria for this review, and 31 studies were included in the meta-analysis. Random-effects meta-analysis was used to assess the quantitative relationships. Subgroup analyses were performed to gain insight into heterogeneity derived from exposure assessment methods (grouped by land use regression [LUR]-models, aerosol optical depth [AOD]-based models, interpolation/dispersion/Bayesian models, and data from monitoring stations), study regions, and concentrations of PM_2.5 exposure. The overall pooled estimate involving 23,925,941 newborns showed that TBW was negatively associated with PM_2.5 exposure (per 10 μg/m³ increment) during the entire pregnancy (β = -16.54 g), but with high heterogeneity (I² = 95.6%). The effect estimate in the LUR-models subgroup (β = -16.77 g) was the closest to the overall estimate and with less heterogeneity (I² = 18.3%) than in the other subgroups of AOD-based models (β = -41.58 g; I² = 95.6%), interpolation/dispersion models (β = -10.78 g; I² = 86.6%), and data from monitoring stations (β = -11.53 g; I² = 97.3%). Even PM_2.5 exposure levels of lower than 10 μg/m³ (the WHO air quality guideline value) had adverse effects on TBW. The LUR-models subgroup was the only subgroup that obtained similar significant of negative associations during the three trimesters as the overall trimester-specific analyses. In conclusion, TBW was negatively associated with maternal PM_2.5 exposures during the entire pregnancy and each trimester. More studies based on relatively standardized exposure assessment methods need to be conducted to further understand the precise susceptible exposure time windows and potential mechanisms.

Exposure to PM2.5 during Pregnancy and Fetal Growth in Eastern Massachusetts, USA

BACKGROUND

Prior studies have examined the association between fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] and fetal growth with either limited spatial or temporal resolution.

OBJECTIVES

In this study, we examined the association between PM2.5 exposure during pregnancy and fetal growth measures (ultrasound parameters and birth weight) in a pregnancy cohort using spatiotemporally resolved PM2.5 in Eastern Massachusetts, USA.

METHODS

We used ultrasound measures of biparietal diameter (BPD), head circumference, femur length, and abdominal circumference (AC), in addition to birth weight, from 9,446 pregnancies that were delivered at the Beth Israel Deaconess Medical Center from 2011-2016. We used linear mixed-effects models to examine the associations of PM2.5 in two exposure windows (the first 16 wk of pregnancy and the cumulative exposure up until the assessment of fetal growth) with anatomic scans (ultrasound measures at<24 wk), growth scans (ultrasound measures at≥24wk), and birth weight. All models were adjusted for sociodemographic characteristics, long-term trends, and temperature.

RESULTS

Higher PM2.5 exposure in the first 16 wk was associated with smaller fetal growth measures, where associations were particularly strong for BPD, AC, and birth weight. For example, a 5-μg/m3 increase in PM2.5 was associated with a lower mean BPD z-score of -0.19 (95% CI: -0.31, -0.06) before 24 wk, a lower mean AC z-score of -0.15 (95% CI: -0.28, -0.01) after 24 wk, and a lower mean birth weight z-score of -0.11 (95% CI: -0.20, -0.01). Analyses examining the associations with cumulative PM2.5 exposure up until the assessment of fetal growth produced attenuated associations.

CONCLUSIONS

Higher gestational exposure to PM2.5 was associated with smaller fetal growth measures at levels below the current national standards. https://doi.org/10.1289/EHP9824.

Weekly-specific ambient fine particular matter exposures before and during pregnancy were associated with risks of small for gestational age and large for gestational age: results from Project ELEFANT

BACKGROUND

Investigations on the potential effects of ambient fine particulate matter (PM2.5) on large for gestational age (LGA) are limited. Furthermore, no study has explored weekly-specific susceptible exposure windows for small for gestational age (SGA) and LGA. This study evaluated the associations of exposure to ambient PM2.5 over the preconception and entire-pregnancy periods with risks of SGA and LGA, as well as explored critical weekly-specific exposure windows.

METHODS

10 916 singleton pregnant women with 24-42 completed gestational weeks from the Project Environmental and LifEstyle FActors iN metabolic health throughout life-course Trajectories between 2014 and 2016 were included in this study. Distributed lag models (DLMs) incorporated in Cox proportional-hazards models were applied to explore the associations of maternal exposure to weekly ambient PM2.5 throughout 12 weeks before pregnancy and pregnancy periods with risks of SGA and LGA after controlling for potential confounders.

RESULTS

For a 10-μg/m3 increase in maternal exposure to PM2.5, positive associations with SGA were observed during the 1st to 9th preconceptional weeks and the 1st to 2nd gestational weeks (P<0.05), with the strongest association in the 5th preconceptional week [hazard ratio (HR), 1.06; 95% confidential interval (CI), 1.03-1.09]. For LGA, positive associations were observed during the 1st to 12th preconceptional weeks and the 1st to 5th gestational weeks (P<0.05), with the strongest association in the 7th preconceptional week (HR, 1.10; 95% CI, 1.08-1.12).

CONCLUSIONS

Exposure to high-level ambient PM2.5 is associated with increased risks of both SGA and LGA, and the most susceptible exposure windows are the preconception and early-pregnancy periods.

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.

The association of prenatal exposure to particulate matter with infant growth: A birth cohort study in Beijing, China

Limited studies examined the associations of prenatal exposure to particulate matter (PM) and children's growth with inconsistent results, and no study focused on PM₁. We matched a birth cohort (10,547 children) with daily PM₁ and PM_2.5 concentrations by maternal home addresses. Air pollution concentrations were predicted by satellite remote sensing data, meteorological factors, and land use information. The weight and length of children in the birth cohort were measured at approximately one year old. We calculated the Z-score of weight for length (WFL) and body mass index (BMI) and then defined overweight and obesity (OWOB) based on WHO Standards. Generalized linear regression and modified Poisson regression were used to identify the association of prenatal exposure to PM₁ or PM_2.5 with anthropometric measurements and risk of OWOB. We also determined the mediation effect of preterm birth on the associations. Results showed that a 10 μg/m³ increase in prenatal exposure to PM₁ and PM_2.5 was significantly associated with a 0.105 [95% confidence interval (CI): 0.067, 0.144] and 0.063 (95% CI: 0.029, 0.097) increase in WFL Z-score for one-year-old children. Similar associations were found for BMI Z-score. A 10 μg/m³ increase in prenatal PM₁ and PM_2.5 exposure was significantly associated with 1.012 (95%CI: 1.003, 1.021) and 1.010 (95%CI: 1.002, 1.018) times higher risk of OWOB. . Preterm birth mediated 7.5% [direct effect (DE) = 0.106, P < 0.001; indirect effect (IE) = 0.009, P < 0.001)] and 9.9% (DE = 0.064, P < 0.001; IE = 0.007, P < 0.001) of the association between prenatal PM₁ and PM_2.5 exposure and WFL Z-score of the children. The association of prenatal PM₁ and PM_2.5 exposure with BMI Z-score of children was also mediated by preterm birth by 6.6% (DE = 0.111, P < 0.001; IE = 0.008, P < 0.001) and 9.1% (DE = 0.064, P < 0.001; IE = 0.006, P < 0.001). These results remained robust in the sensitivity analyses. In conclusion, prenatal exposure to PM₁ and PM_2.5 increased WFL, BMI Z-scores and higher risk of OWOB for one-year-old children. The associations were partially mediated by preterm birth. These findings call for the urgent action on air pollution regulation to protect early-life health among children.

Associations of adverse pregnancy outcomes with high ambient air pollution exposure: Results from the Project ELEFANT

BACKGROUND

Investigations on the potential effects of high air pollution exposure before pregnancy on adverse pregnancy outcomes are limited, and it is unknown whether air quality standards looser than that set by World Health Organization (WHO) still can provide sufficient protection pregnant women from adverse pregnancy outcomes.

OBJECTIVES

To evaluate the potential effects of high ambient air pollution around pregnancy on preterm birth (PTB) and low birth weight (LBW), and assess the risk of PTB and LBW associated with air pollutants with reference to different air quality standards of WHO and China.

METHODS

Our study leveraged 10,960 pregnant women from the Project ELEFANT. Daily average particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO) and ozone (O₃) concentrations were collected based on Chinese Air Quality Reanalysis datasets. Hazard ratios (HR) of PTB and LBW were estimated for maternal PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃ exposures and related proportions of days with daily average air pollution concentrations exceeding air quality standards of WHO and China around pregnancy using Cox proportional hazards regression models with adjustment for potential confounders.

RESULTS

Ambient PM_2.5, PM₁₀, NO₂, SO₂ and CO exposure during the before pregnancy and pregnancy period were both significantly and positively associated with increased risk of PTB, PTB subtypes and LBW. A 10% increase in proportion of days with daily average PM_2.5 exceeding 25 μg/m³ over the entire pregnancy was most apparently associated with risk of PTB (HR, 12.66; 95% CI, 8.20-19.53) and LBW (HR, 17.42; 95% CI, 6.88-44.10) among all PM_2.5 proportion variables based on different air quality standards.

CONCLUSION

Air quality standards of WHO are necessary to be implemented to control for risks of adverse pregnancy outcomes associated with ambient air pollution in areas with high air pollution levels.

Association between residential greenness and glycosylated hemoglobin in pregnant women: Findings from the baseline data of Yuexiu birth cohort

BACKGROUND

Previous studies have indicated that residential greenness can affect human health, but limited studies have examined the association between residential greenness and glucose homeostasis during pregnancy. We aimed to investigate the associations of residential greenness with plasma glucose, glycosylated hemoglobin (HbA1c) and gestational diabetes mellitus (GDM).

METHODS

We recruited a total of 587 pregnant women aged 20-45 years in Guangzhou, China. We extracted normalized difference vegetation index with different buffers (NDVI-250m, 500m and 1000m) from remote satellite data based on maternal residential addresses. We measured plasma glucose levels and HbA1c during 20-28 weeks' gestation, and GDM was diagnosed with a 75-g oral glucose tolerance test. We collected the information of relevant covariates by face-to-face interviews and questionnaires. We used generalized linear regression to examine the associations of residential greenness with quantitative and categorized outcomes.

RESULTS

In the final analyses, 123 (21.0%) of the pregnant women were diagnosed as GDM at 20-28 weeks gestation. With a 0.1 unit increase in NDVI-250m, the percent of HbA1c changed by -0.05% [95% confidence interval (CI): -0.08, -0.02]. The results of HbA1c were consistent when using different resolution of NDVI [NDVI-500m: 0.03, 95%CI: -0.05, -0.01; NDVI-1000m: 0.05, 95%CI: -0.08, -0.02]. We observed non-significant associations of glucose levels and the risk of GDM in relation to NDVI with different resolutions when adjusted for confounding. The results remained robust in sensitivity analyses.

CONCLUSION

The present study in Guangzhou, China was the first to identify negative association of NDVI with HbA1c in pregnant women, but we did not observe its association with plasma glucose levels or the risk of GDM. The results support that building sufficient green infrastructure could be considered in urban design and planning to promote maternal health.

Prenatal exposure to air pollutants and early childhood growth trajectories: A population-based prospective birth cohort study

BACKGROUND

Air pollution exposure during pregnancy has been documented to be associated with impaired fetal growth and adverse birth outcomes, but the evidence regarding the effects of air pollution on early childhood growth is still limited.

OBJECTIVE

We aimed to explore the associations of exposure to air pollutants during pregnancy with childhood growth trajectories from birth to age of 6 years.

METHODS

A prospective cohort study based on the administrative registration system was conducted covering 62,540 births in Wuhan, China between January 1, 2011 and December 31, 2013 and followed for 6 years. Inverse distance weighted method was used to estimate the concentrations of air pollutants exposure for pregnant women. Group-based trajectory models (GBTM) were used to identify growth patterns of children: slow growth, normal growth, and rapid growth. Multinomial logistic regression models were used to examine the associations between prenatal exposure to air pollutants and childhood growth trajectories with adjustment for maternal age, educational status, pre-pregnancy BMI, residential areas, gestational diabetes, birth type, gender of infant, and breastfeeding duration.

RESULTS

The mean (SD) of prenatal exposure concentrations for PM₁₀, SO₂, NO₂, CO, and O₃ were 107.9 (30.4), 32.8(12.6), 55.8(13.1), 1081.2(293.1), and 81.6(31.0) μg/m³ respectively. Compared with normal growth trajectory, increased PM₁₀ and CO exposure were significantly associated with higher risk of slow growth trajectory but lower risk of rapid growth trajectory. An increase in prenatal exposure to NO₂ significantly increased both the risk of slow growth trajectory and rapid growth trajectory. Increased prenatal SO₂ exposure was significantly associated with rapid growth trajectory and was not associated with low growth trajectory. With O₃ exposure levels increased, risk to be rapid growth trajectory decreased. Prenatal air pollutants exposure had a greater impact on childhood growth of children who were girls, and those mothers lived in rural areas and were normal weight before pregnancy.

CONCLUSIONS

High levels of air pollutants exposure during pregnancy were associated with the risk of being in a trajectory with the deviation of BMI gain from birth to 6 years old. These findings suggest that efforts to identify children at risk of growth deviation in early childhood should pay attention to environmental exposure during pregnancy for their mothers.

Prenatal exposure to airborne particulate matter of 1 μm or less and fetal growth: A birth cohort study in Beijing, China

BACKGROUND

The association of airborne particulate matter of 1 μm or less (PM₁) with fetal growth hasn't been studied. We aimed to investigate the association of PM₁ with fetal growth parameters measured via ultrasonography and birth weight.

METHODS

The birth cohort included 18,669 pregnant women who were pregnant between 2014 and 2017 in Tongzhou Maternal and Child Health Hospital of Beijing, China. The predicted PM₁ concentration was matched with the residential addresses of each woman. The fetal abdominal circumference (AC), head circumference (HC), femur length (FL) and estimated fetal weight (EFW) were evaluated via ultrasonography, while birth weight was measured at birth. The fetal parameters and birth weight were standardized as gestational-age- and gender-adjusted Z-score. We defined undergrowth of fetal parameters, low birth weight (LBW) and small-for-gestational-age (SGA) as categorized outcomes. Generalized estimating equations and generalized linear regression were used to examine the associations of PM₁ with quantitative and categorized outcomes, respectively.

RESULTS

A 10 μg/m³ increase in PM₁ was associated with decrement in the Z-scores of AC [-0.027, 95% confidence intervals (CI): -0.047~ -0.07]EFW (-0.055, 95%CI: -0.075~-0.035). These results remained robust after adjusting nitrogen dioxide and sulphur dioxide. We didn't observe significant results regarding the analyses of undergrowth of all fetal parameters and the analyses of birth weight outcomes.

CONCLUSION

This study identified the negative associations between PM₁ and fetal parameters in utero. The findings provided robust evidence that strategies for reducing PM₁ exposure can prevent early-life health.

The mediation effect of maternal glucose on the association between ambient air pollution and birth weight in Foshan, China

Maternal blood glucose level is associated with fetal growth, therefore, its role in the associations between air pollution and birth weight deserves investigation. We examined the mediation effect of maternal blood glucose on the associations between maternal air pollution exposure and birth weight. A total of 10,904 pregnant women in Foshan, China during 2015-2019 were recruited. Oral glucose tolerance test (OGTT) was administered to each participant after late trimester 2. Air pollution data at the monitoring stations in residential districts was used to estimate exposures of each participant during trimester 1 and trimester 2. Mixed-effects linear models were used to estimate the associations between air pollution and birth weight. After controlling for ten covariates, the direct effect of PM_2.5 and SO₂ (each 10 μg/m³ increment) on birth weight was -15.7 g (95% CI: -29.4, -4.8 g) and -83.6 g (95% CI: -134.8, -33.0 g) during trimester 1. The indirect effect of PM_2.5 and SO₂ (each 10 μg/m³ increment) on birth weight by increasing maternal fasting glucose level was 6.6 g (95% CI: 4.6, 9.1 g) and 22.0 g (95% CI: 4.1, 44.0 g) during trimester 1. Our findings suggest that air pollution might affect the birth weight through direct and indirect pathway, and the indirect effect might be mediated by maternal blood glucose.

Maternal exposure to air pollution and the risk of low birth weight: A meta-analysis of cohort studies

Previous studies have evaluated the relationship between prenatal air pollution exposure and low birth weight, but the results are inconsistent. The purpose of this meta-analysis is to quantitatively analyze the relationship between maternal air pollutant exposure and low birth weight (LBW). PubMed and Web of Science databases were searched to obtain the studies on the relationship between the prenatal exposure of air pollutants and LBW that published as of June 2020. The pooled effects of air pollutant exposure and LBW were calculated using random-effect model (for studies with significant heterogeneity) or fixed-effect model (for studies without significant heterogeneity). Totally, 54 studies were included in this meta-analysis. The pooled effect of PM_2.5, PM₁₀, NO₂, CO, SO₂, and O₃ exposure on LBW were 1.081 (95% CI: 1.043, 1.120), 1.053 (95% CI: 1.030, 1.076), 1.030 (95% CI: 1.008, 1.053), 1.007 (95% CI: 1.001, 1.014), 1.125 (95% CI: 1.017, 1.244), and 1.045 (95% CI: 1.005, 1.086), respectively. NO₂ (per 10 ppb increase) and CO (per 100 ppb increase) exposure in the first trimester were positively correlated with LBW, of which the pooled effect was 1.022 (95% CI: 1.009, 1. 035) and 1.008 (95% CI: 1.004, 1.012), respectively. PM_2.5 (per 10 μg/m³ increase) exposure in the third trimester significantly affected the LBW, of which the pooled effect was 1.053 (95% CI: 1.010, 1.097). In addition, PM₁₀ (per 10 μg/m³ increase) exposure in the second trimester also significantly affected the LBW, with the pooled effect of 1.011 (95% CI: 1.005, 1.017). Prenatal exposure of the major air pollutants during the entire pregnancy could increase the risk of LBW, while the susceptible window of the pollutants varied.

Ambient air pollution exposed during preantral-antral follicle transition stage was sensitive to associate with clinical pregnancy for women receiving IVF

Maternal exposure to air pollution is associated with poor reproductive outcomes in in vitro fertilization (IVF). However, the susceptible time windows are still not been known clearly. In the present study, we linked the air pollution data with the information of 9001 women receiving 10,467 transfer cycles from August 2014 to August 2019 in The Second Hospital of Hebei Medical University, Shijiazhuang City, China. Maternal exposure was presented as individual average daily concentrations of PM_2.5, PM₁₀, NO₂, SO₂, CO, and O_3, which were predicted by spatiotemporal kriging model based on residential addresses. Exposure windows were divided to five periods according to the process of follicular and embryonic development in IVF. Generalized estimating equation model was used to evaluate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for association between clinical pregnancy and interquartile range increased average daily concentrations of pollutants during each exposure period. The increased PM_2.5 (adjusted OR = 0.95, 95% CI: 0.90, 0.99), PM₁₀ (adjusted OR = 0.93, 95% CI: 0.89, 0.98), NO₂ (adjusted OR = 0.89, 95% CI: 0.85, 0.94), SO₂ (OR = 0.94, 95% CI: 0.90, 0.98), CO (adjusted OR = 0.93, 95% CI: 0.89, 0.97) whereas decreased O₃ (OR = 1.08, 95% CI: 1.02, 1.14) during the duration from preantral follicles to antral follicles were the strongest association with decreased probability of clinical pregnancy among the five periods. Especially, women aged 20-29 years old were more susceptible in preantral-antral follicle transition stage. Women aged 36-47 years old were more vulnerable during post-oocyte retrieve period. Our results suggested air pollution exposure during preantral-antral follicle transition stage was a note-worthy challenge to conceive among females receiving IVF.