Association between early prenatal exposure to ambient air pollution and birth defects: evidence from newborns in Xi'an, China

Exploring potential causal links between air pollutants and congenital malformations: A two-sample Mendelian Randomization study

Observational studies have suggested an association between air pollutants and congenital malformations; however, conclusions are inconsistent and the causal associations have not been elucidated. In this study, based on publicly available genetic data, a two-sample Mendelian randomization (MR) was applied to explore the associations between particulate matter 2.5 (PM2.5), NOX, NO2 levels and 11 congenital malformations. Inverse variance weighted (IVW), MR-Egger and weighted median were used as analytical methods, with IVW being the main method. A series of sensitivity analyses were used to verify the robustness of the results. For significant associations, multivariable MR (MVMR) was utilized to explore possible mediating effects. The IVW results showed that PM2.5 was associated with congenital malformations of digestive system (OR = 7.72, 95 %CI = 2.33-25.54, P = 8.11E-4) and multiple systems (OR = 8.63, 95 %CI = 1.02-73.43, P = 0.048) risks; NOX was associated with circulatory system (OR = 4.65, 95 %CI = 1.15-18.86, P = 0.031) and cardiac septal defects (OR = 14.09, 95 %CI = 1.62-122.59, P = 0.017) risks; NO2 was correlated with digestive system (OR = 27.12, 95 %CI = 1.81-407.07, P = 0.017) and cardiac septal defects (OR = 22.57, 95 %CI = 2.50-203.45, P = 0.005) risks. Further MVMR analyses suggest that there may be interactions in the effects of these air pollutants on congenital malformations. In conclusion, this study demonstrated a causal association between air pollution and congenital malformations from a genetic perspective.

Lead brownfields and birth defects in North Carolina 2003-2015: A cross-sectional case-control study

BACKGROUND

Brownfields consist of abandoned and disused sites, spanning many former purposes. Brownfields represent a heterogenous yet ubiquitous exposure for many Americans, which may contain hazardous wastes and represent urban blight. Neonates and pregnant individuals are often sensitive to subtle environmental exposures. We evaluate if residential exposure to lead (Pb) brownfields is associated with birth defects.

METHODS

Using North Carolina birth records from 2003 to 2015, we sampled 169,499 births within 10 km of a Pb brownfield with 3255 cardiovascular, central nervous, or external defects identified. Exposure was classified by binary specification of residing within 3 km of a Pb brownfield. We utilized multivariable logistic regression models adjusted for demographic covariates available from birth records and 2010 Census to estimate odds ratios (OR) and 95% confidence intervals (CI). Effect measure modification was assessed by inclusion of interaction terms and stratification for the potential modifiers of race/ethnicity and diabetes status.

RESULTS

We observed positive associations between cardiovascular birth defects and residential proximity to Pb brownfields, OR (95%CI): 1.15 (1.04, 1.26), with suggestive positive associations for central nervous 1.16 (0.91, 1.47) and external defects 1.19 (0.88, 1.59). We did observe evidence of effect measure modification via likelihood ratio tests (LRT) for race/ethnicity for central nervous and external defect groups (LRT p values 0.08 and 0.02). We did observe modification by diabetes status for the cardiovascular group (LRT p value 0.08).

CONCLUSIONS

Our results from this analysis indicate that residential proximity to Pb brownfields is associated with cardiovascular birth defects with suggestive associations for central nervous and external defects. In-depth analyses of individual defects and other contaminants or brownfield site functions may reveal additional novel associations.

Global air pollution exposure and congenital anomalies: an updated systematic review and meta-analysis of epidemiological studies

A systematic review and meta-analysis was conducted to evaluate recent epidemiological evidence on the association of air pollution with congenital anomalies (CAs). Of 11,014 records, 49 were finally included in this meta-analysis. Per 10 μg/m3 increase in air pollutant, PM10 exposure during the 1st month of pregnancy and at the first trimester (T1) was associated with increased overall CAs. Further, exposure to PM10 was associated with congenital heart disease (OR = 1.055, 95% CI: 1.035, 1.074) and patent ductus arteriosus (OR = 1.094, 95% CI: 1.020, 1.168) at T1, with chromosomal anomalies during the entire pregnancy and with nervous system anomalies when exposure occurred 3 months prior to pregnancy, during the 1st, 2nd months of pregnancy and at T1. Besides, a significant association with overall CAs was observed for a combined exposure of PM10 and SO2 during the 1st month of gestation (OR: 1.101, 95% CI: 1.023, 1.180). A combined exposure of PM10 and CO was also associated with tetralogy of Fallot during 3-8 weeks of gestation (OR: 1.016, 95% CI: 1.005, 1.027). No significant associations were observed between PM2.5, NO2, and O3 exposure and CAs.

Environmental Signals

Environmental factors have long been known to play a role in the pathogenesis of congenital heart disease (CHD), but this has not been a major focus of research in the modern era. Studies of human exposures and animal models demonstrate that demographics (age, race, socioeconomic status), diseases (e.g., diabetes, hypertension, obesity, stress, infection, high altitude), recreational and therapeutic drug use, and chemical exposures are associated with an increased risk for CHD. Unfortunately, although studies suggest that exposures to these factors may cause CHD, in most cases, the data are not strong, are inconclusive, or are contradictory. Although most studies concentrate on the effects of maternal exposure, paternal exposure to some agents can also modify this risk. From a mechanistic standpoint, recent delineation of signaling and genetic controls of cardiac development has revealed molecular pathways that may explain the effects of environmental signals on cardiac morphogenesis and may provide further tools to study the effects of environmental stimuli on cardiac development. For example, environmental factors likely regulate cellular signaling pathways, transcriptional and epigenetic regulation, proliferation, and physiologic processes that can control the development of the heart and other organs. However, understanding of the epidemiology and risk of these exposures and the mechanistic basis for any effects on cardiac development remains incomplete. Further studies defining the relationship between environmental exposures and human CHD and the mechanisms involved should reveal strategies to prevent, diagnose, and treat CHD induced by environmental signals.

Association between gestational exposure and risk of orofacial clefts: a systematic review and meta-analysis

BACKGROUND

The occurrence of orofacial Clefts (OFCs) is a congenital disease caused by many factors. According to recent studies, air pollution has a strong correlation with the occurrence of OFCs. However, there are still some controversies about the current research results, and there is no relevant research to review the latest results in recent years.

OBJECTIVE

In this paper, the authors conducted a systematic review and meta-analysis to explore the correlation between ambient air pollution and the occurrence of neonatal OFCs deformity.

METHODS

We searched Pubmed, Web of science, and Embase databases from the establishment of the database to May 2023. We included observational studies on the relationship between prenatal exposure to fine particulate matter 2.5 (PM2.5), fine particulate matter 10 (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and the risk of cleft lip (CL), cleft palate (CP), cleft lip with or without palate (CL/P). the Newcastle-Ottawa quality assessment scale (NOS) was used to evaluate the quality of the literature. Funnel plot and Egger's regression were used to verify the publication bias. Random effect model or fixed effect model was used to estimate the combined relative risk (RR) and 95% confidence interval (95%CI).

RESULTS

A total of eleven studies were included in this study, including four cohort studies and seven case-control studies, including 22,453 cases of OFCs. Ten studies had low risk of bias and only one study had high risk of bias. Three studies reported that PM2.5 was positively correlated with CL and CP, with a combined RR and 95%CI of 1.287(1.174,1.411) and 1.267 (1.105,1.454). Two studies reported a positive correlation between O3 and CL, with a combined RR and 95%CI of 1.132(1.047,1.225). Two studies reported a positive correlation between PM10 and CL, with a combined RR and 95%CI of 1.108 (1.017,1.206). No association was found between SO2, CO, NO2 exposure during pregnancy and the risk of OFCs.

CONCLUSION

The results of this study showed that there was a significant statistical correlation between exposure to PM10, PM2.5, O3 and the risk of OFCs in the second month of pregnancy. Exposure assessment, research methods and mechanisms need to be further explored.

Cumulative effect of PM2.5 components is larger than the effect of PM2.5 mass on child health in India

While studies on ambient fine particulate matter (PM2.5) exposure effect on child health are available, the differential effects, if any, of exposure to PM2.5 species are unexplored in lower and middle-income countries. Using multiple logistic regression, we showed that for every 10 μg m-3 increase in PM2.5 exposure, anaemia, acute respiratory infection, and low birth weight prevalence increase by 10% (95% uncertainty interval, UI: 9-11), 11% (8-13), and 5% (4-6), respectively, among children in India. NO3-, elemental carbon, and NH4+ were more associated with the three health outcomes than other PM2.5 species. We found that the total PM2.5 mass as a surrogate marker for air pollution exposure could substantially underestimate the true composite impact of different components of PM2.5. Our findings provide key indigenous evidence to prioritize control strategies for reducing exposure to more toxic species for greater child health benefits in India.

Association between air pollutants and birth defects in Xiamen, China

Objective

To explore the relationship between common air pollution and common birth defects, and to provide reference for the prevention of birth defects.

Methods

We conducted a case-control study in Xiamen, a city in southeastern China from 2019 to 2020. Logistics regression was used to analyze the relationship between sulfur dioxide(SO₂), fine particulate matter 2.5(PM_2.5), nitrogen dioxide(NO₂), ozone(O₃), carbon monoxide(CO) and the occurrence of common birth defects such as congenital heart disease, facial cleft, and finger deformity.

Results

SO₂ significantly increased the risk of birth defects such as congenital heart disease, cleft lip and/or cleft palate, and ear deformity in the first and second months of pregnancy.

Conclusion

Exposure to common air pollutants increases the risk of birth defects, and SO₂ significantly affects the occurrence of birth defects in the first two months of pregnancy.

Ambient air pollutants in the first trimester of pregnancy and birth defects: an observational study

OBJECTIVES

As current studies on the relationships between air pollutants exposure during the first trimester and birth defects were not fully elucidated, this study aimed to assess the association between selected air pollutants and birth defects.

DESIGN

An observational study.

PARTICIPANTS

We obtained 70 854 singletons with gestational age <20 weeks who were delivered at a large maternal and child healthcare centre in Wuhan, China.

OUTCOME MEASURES

Birth defects data and daily average concentration of ambient particulate matter ≤10 µm diameter (PM₁₀), PM ≤2.5 µm diameter (PM_2.5), sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) were obtained. Logistic regression analysis was applied to assess the association between maternal air pollutants exposure during first trimester and total birth defects, congenital heart defects (CHDs), limb defects and orofacial clefts with adjustments of potential covariates.

RESULTS

There were a total of 1352 birth defect cases included in this study, with a prevalence of 19.08‰. Maternal exposed to high concentrations of PM₁₀, PM_2.5, NO₂ and SO₂ in the first trimester were significantly associated with elevated ORs of birth defects (ORs ranged from 1.13 to 1.23). Additionally, for male fetuses, maternal exposed to high PM_2.5 concentration was associated with an elevated odd of CHDs (OR 1.27, 95% CI 1.06 to 1.52). In the cold season, the ORs of birth defects were significantly increased among women exposed to PM_2.5 (OR 1.64, 95% CI 1.41 to 1.91), NO₂ (OR 1.22, 95% CI 1.08 to 1.38) and SO₂ (OR 1.26, 95% CI 1.07 to 1.47).

CONCLUSIONS

This study showed unfavourable effects of air pollutants exposure during the first trimester on birth defects. Especially, the association between maternal PM_2.5 exposure and CHDs was only observed among male fetuses, and stronger effects of PM_2.5, NO₂ and SO₂ exposure on birth defects were observed in the cold season.

Association between air pollutants and neural tube defects during pregnancy in Lanzhou, China: a time series analysis

Few studies have evaluated the association between air pollutants and neural tube defects (NTDs). Moreover, the existing research ignores the lag effect of air pollution on health and provides inconsistent epidemiological evidence. We aim to estimate the association between air pollution and NTDs during the first trimester of pregnancy and identify specific susceptible windows. Birth data was collected from the Birth Defects Surveillance Network in Lanzhou from September 1, 2014, to December 31, 2019. Air quality and meteorological data were collected from ambient air monitoring stations and China Meteorological Data Network. The log connection function of the Poisson distribution function is used to establish a DLNM model to estimate the exposure-effect relationship and exposure-lag relationship association between air pollutants levels and NTDs. There were 320,787 perinatal infants in Lanzhou from September 1, 2014, to December 31, 2019, and 486 cases of NTDs (1.5‰). The result indicates that exposure to inhalable particles (PM₁₀) at lag 2-4 weeks was significantly associated with the risk of NTDs, with the most significant impact at the lag 2 week (RR=1.048, 95%CI, 1.015-1.084). Exposure to fine particulate matter (PM_2.5) at the lag 2 week was significantly associated with the risk of NTDs, with the most significant impact at the lag 2 week (RR=1.077, 95%CI, 1.004-1.155). Exposure to sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) at lag 3-6weeks was significantly associated with the risk of NTDs, with the most significant impact at the lag 4 week (RR=1.220, 95%CI, 1.105-1.348; RR=1.143, 95%CI, 1.048-1.245). This study provides further evidence that exposure to air pollutants in the first trimester of pregnancy significantly increases the risk of neural tube defects.

Early prenatal exposure to air pollutants and congenital heart disease: a nested case-control study

BACKGROUND

Congenital heart disease (CHD) is one of the most common congenital malformations in humans. Inconsistent results emerged in the existed studies on associations between air pollution and congenital heart disease. The purpose of this study was to evaluate the association of gestational exposure to air pollutants with congenital heart disease, and to explore the critical exposure windows for congenital heart disease.

METHODS

The nested case-control study collected birth records and the following health data in Tianjin Women and Children's Health Center, China. All of the cases of congenital heart disease from 2013 to 2015 were selected matching five healthy controls for each case. Inverse distance weighting was used to estimate individual exposure based on daily air pollution data. Furthermore, the conditional logistic regression with distributed lag non-linear model was performed to identify the association between gestational exposure to air pollution and congenital heart disease.

RESULTS

A total of 8,748 mother-infant pairs were entered into the analysis, of which 1,458 infants suffered from congenital heart disease. For each 10 µg/m³ increase of gestational exposure to PM_2.5, the ORs (95% confidence interval, 95%CI) ranged from 1.008 (1.001-1.016) to 1.013 (1.001-1.024) during the 1^st-2^nd gestation weeks. Similar weak but increased risks of congenital heart disease were associated with O₃ exposure during the 1^st week and SO₂ exposure during 6^th-7^th weeks in the first trimester, while no significant findings for other air pollutants.

CONCLUSIONS

This study highlighted that gestational exposure to PM_2.5, O₃, and SO₂ had lag effects on congenital heart disease. Our results support potential benefits for pregnancy women to the mitigation of air pollution exposure in the early stage, especially when a critical exposure time window of air pollutants may precede heart development.

Time series analysis on association between ambient air pollutants and orofacial clefts during pregnancy in Lanzhou, China

Current studies on air pollutant exposure during pregnancy and orofacial clefts (OFCs) have inconsistent results, and few studies have investigated refined susceptible windows for OFCs. We aim to estimate association between air pollution and OFCs during the first trimester of pregnancy and identify specific susceptible windows. Birth data was obtained from Birth Defects Surveillance Network in Lanzhou from 2014 to 2019. Air pollution data and temperature data were obtained from ambient air monitoring stations and China Meteorological Data Network, respectively. A distribution lag nonlinear model (DLNM) was applied to estimate weekly-exposure-lag-response association between air pollutant levels and OFCs. The study included 320,787 perinatal infants from 2014 to 2019, of which 685 (2.14‰) were OFCs. The results demonstrated that exposure of pregnant women to aerodynamic diameter ≤ 10 μm (PM₁₀) at lag 4-5 weeks was significantly associated with the risk of OFCs, with the greatest impact at the lag 4 week (RR = 1.029, 95% CI = 1.001-1.057). Exposure to sulfur dioxide (SO₂) at lag 2-4 weeks was significantly associated with the risk of OFCs, with the greatest impact at the lag 3 week (RR = 1.096, 95% CI = 1.041-1.177). This study provides further evidence that exposure to air pollution increases the risk of OFCs in the first trimester of pregnancy.

Risk Assessment for Birth Defects in Offspring of Chinese Pregnant Women

Objective: This study aimed to develop a nomogram for the risk assessment of any type of birth defect in offspring using a large birth-defect database in Northwest China. Methods: This study was based on a birth-defect survey, which included 29,204 eligible women who were pregnant between 2010 and 2013 in the Shaanxi province of Northwest China. The participants from central Shaanxi province were assigned to the training group, while the subjects from the south and north of Shaanxi province were assigned to the external validation group. The primary outcome was the occurrence of any type of birth defect in the offspring. A multivariate logistic regression model was used to establish a prediction nomogram, while the discrimination and calibration were evaluated by external validation. Results: The multivariate analyses revealed that household registration, history of miscarriages, family history of birth defects, infection, taking medicine, pesticide exposure, folic acid supplementation, and single/twin pregnancy were significant factors in the occurrence of birth defects. The area under the receiver operating characteristic curve (AUC) in the prediction model was 0.682 (95% CI 0.653 to 0.710) in the training set. The validation set showed moderate discrimination, with an AUC of 0.651 (95% CI 0.614 to 0.689). Additionally, the prediction model had a good calibration (HL χ2 = 8.106, p= 0.323). Conclusions: We developed a nomogram risk model for any type of birth defect in a Chinese population based on important modifying factors in pregnant women. This risk-prediction model could be a tool for clinicians to assess the risk of birth defects and promote health education.

Maternal Exposure to Sulfur Dioxide and Risk of Omphalocele in Liaoning Province, China: A Population-Based Case-Control Study

Evidence of the association between maternal sulfur dioxide (SO₂) exposure and the risk of omphalocele is limited and equivocal. We aimed to assess the aforementioned topic during the first trimester of pregnancy. A population-based case-control study was carried out in infants consisting of 292 cases of omphalocele and 7,950 healthy infant controls. Exposure to SO₂, particulate matter with aerodynamic diameters ≤ 10 μm, and nitrogen dioxide was assessed by averaging the concentration from all stations in the mother's residential city. SO₂ exposure was categorized into three groups, with the lowest tertile defined as the reference category. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using multivariable logistic regression models. Higher SO₂ exposure during the first trimester was significantly associated with omphalocele risk [per standard deviation (42 ug/m³) increment: OR = 1.39, 95% CI = 1.22–1.65]. When focusing on shorter exposure windows, similar positive associations were observed for SO₂ exposure in the first and third months of pregnancy. In addition, compared with the lowest tertile, high SO₂ exposure in the second month of pregnancy increased the risk of omphalocele (OR = 2.80, 95% CI = 1.61–4.97). Maternal exposure to SO₂ during the first trimester may increase the risk of omphalocele in offspring.

Association between maternal exposure to PM10 and risk of anorectal atresia/stenosis in offspring: a population-based case-control study in Liaoning Province, China

The potential association between maternal exposure to PM₁₀ ranging from 3 months prior to conception to the end of the early trimester and the risk of anorectal atresia/stenosis in offspring has not been established. Thus, we determined the association between maternal exposure to PM₁₀ and risk of anorectal atresia/stenosis in offspring in this study. We recruited 713 patients including 480 male and 233 female with anorectal atresia/stenosis and 7950 randomly selected healthy offspring from the Maternal and Child Health Certificate Registry of Liaoning Province and delivered between 1 January 2010 and 31 December 2015. Monthly PM₁₀ concentrations were retrieved from the Environment Protection Bureau of each city in Liaoning Province. We established a multivariable logistic regression model to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Maternal exposure to PM₁₀ was associated with an increased risk for anorectal atresia/stenosis in offspring during the 3 months prior to conception (per 10 μg/m³ increment: OR = 1.15, 95% CI = 1.03-1.20; per SD [27 μg/m³] increment: OR = 1.33, 95% CI = 1.09-1.63) and the first trimester (per 10 μg/m³ increment: OR = 1.08, 95% CI = 1.00-1.17; per SD [28 μg/m³] increment: OR = 1.26, 95% CI = 1.01-1.57). Evaluation of the association with a shorter exposure window (1 month) revealed a positive association between anorectal atresia/stenosis and PM₁₀ from the 3rd month prior to pregnancy to each month of the 1st trimester. Maternal exposure to PM₁₀ 3 months prior to conception and during the 1st trimester was associated with an increased risk of anorectal atresia/stenosis in the offspring. Future perspective cohort studies are needed to confirm our findings.

A cross-sectional study of brownfields and birth defects

BACKGROUND

Brownfields are a multitude of abandoned and disused sites, spanning many former purposes. Brownfields represent a heterogenous yet ubiquitous exposure for many Americans, which may contain hazardous wastes and represent urban blight. Neonates and pregnant individuals are often sensitive to subtle environmental exposures. We evaluate whether residential brownfield exposure is associated with birth defects.

METHODS

Using North Carolina birth records from 2003 to 2015, we sampled 753,195 births with 39,495 defects identified. We examined defect groups and 30 distinct phenotypes. Number of brownfields within 2,000 m of the residential address at birth was summed. We utilized mixed effects multivariable logistic regression models adjusted for demographic and environmental covariates available from birth records, 2010 Census, and EPA's Environmental Quality Index to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

We observed positive associations between cardiovascular and external defect groups (OR [95% CI]: 1.07 [1.02-1.13] and 1.17 [1.01-1.35], respectively) and any brownfield exposure. We also observed positive associations with atrial septal and ventricular septal defects (1.08 [1.01-1.16] and 1.15 [1.03-1.28], respectively), congenital cataracts (1.38 [0.98-1.96]), and an inverse association with gastroschisis (0.74 [0.58-0.94]). Effect estimates for several additional defects were positive, though we observed null associations for most group and individual defects. Additional analyses indicated an exposure-response relationship for several defects across levels of brownfield exposure.

CONCLUSIONS

Our results indicate that residential proximity to brownfields is associated with birth defects, especially cardiovascular and external defects. In-depth analyses of individual defects and specific contaminants or brownfield sites may reveal additional novel associations.

Association between Maternal Exposure to Ambient Air Pollution and the Risk of Preterm Birth: A Birth Cohort Study in Chongqing, China, 2015-2020

Recent study results on the association between maternal exposure to ambient air pollution with preterm birth have been inconsistent. The sensitive window of exposure and influence level of air pollutants varied greatly. We aimed to explore the association between maternal exposure to ambient air pollutants and the risk of preterm birth, and to estimate the sensitive exposure time window. A total of 572,116 mother–newborn pairs, daily concentrations of air pollutants from nearest monitoring stations were used to estimate exposures for each participant during 2015–2020 in Chongqing, China. We applied a generalized additive model and estimated RRs and 95% CIs for preterm birth in each trimester and the entire pregnancy period. In the single-pollutant model, we observed that each 10 μg/m³ increase in PM_2.5 had a statistically significant effect on the third trimester and entire pregnancy, with RR = 1.036 (95% CI: 1.021, 1.051) and RR = 1.101 (95% CI: 1.075, 1.128), respectively. Similarly, for each 10 μg/m³ increase in PM₁₀, there were 2.7% (RR = 1.027, 95% CI: 1.016, 1.038) increase for PTB on the third trimester, and 3.8% (RR = 1.038, 95% CI: 1.020, 1.057) increase during the whole pregnancy. We found that for each 10 mg/m³ CO increases, the relative risk of PTB increased on the first trimester (RR = 1.081, 95% CI: 1.007, 1.162), second trimester (RR = 1.116, 95% CI: 1.035, 1.204), third trimester (RR = 1.167, 95% CI: 1.090, 1.250) and whole pregnancy (RR = 1.098, 95% CI: 1.011, 1.192). No statistically significant RR was found for SO₂ and NO₂ on each trimester of pregnancy. Our study indicates that maternal exposure to high levels of PM_2.5 and PM₁₀ during pregnancy may increase the risk for preterm birth, especially for women at the late stage of pregnancy. Statistically increased risks of preterm birth were associated with CO exposure during each trimester and entire pregnancy. Reducing exposure to ambient air pollutants for pregnant women is clearly necessary to improve the health of infants.

The association between wildfire exposure in pregnancy and foetal gastroschisis: A population-based cohort study

BACKGROUND

Global climate change has led to an increase in the prevalence and severity of wildfires. Pollutants released into air, soil and groundwater from wildfires may impact embryo development leading to gastroschisis.

OBJECTIVE

The objective of this study was to determine the association between wildfire exposure before and during pregnancy and the risk of foetal gastroschisis development.

METHODS

This was a retrospective cohort study using The California Office of Statewide Health Planning and Development Linked Birth File linked to The California Department of Forestry and Fire Protection data between 2007 and 2010. Pregnancies complicated by foetal gastroschisis were identified by neonatal hospital discharge ICD-9 code. Pregnancies were considered exposed to wildfire if the mother's primary residence zip code was within 15 miles to the closest edge of a wildfire. The exposure was further stratified by trimester or if exposed within 30 days prior to pregnancy. Multivariable log-binomial regression analyses were performed to estimate the association between wildfire exposure in each pregnancy epoch and foetal gastroschisis.

RESULTS

Between 2007 and 2010, 844,348 (40%) births were exposed to wildfire in California. Compared with births without wildfire exposure, those with first-trimester exposure were associated with higher rates of gastroschisis, 7.8 vs. 5.7 per 10,000 births (adjusted relative risk [aRR] 1.28, 95% confidence interval [CI] 1.07, 1.54). Furthermore, those with prepregnancy wildfire exposure were also found to have higher rates of gastroschisis, 12.5 vs. 5.7 per 10,000 births, (aRR 2.17, 95% CI 1.42, 3.52). In contrast, second- and third-trimester wildfire exposures were not associated with foetal gastroschisis.

CONCLUSIONS

Wildfire exposure within 30 days before pregnancy was associated with more than two times higher risk of foetal gastroschisis, whereas a 28% higher risk was demonstrated if exposure was in the first trimester.

Associations between air pollution exposure and birth defects: a time series analysis

Air pollution is a serious environmental problem in China. Birth defects are particularly vulnerable to outdoor air pollution. Our study was to evaluate the association between short-term exposure to air pollutants and the risk of birth defects. Daily data including the air pollutants, meteorological characteristics, and birth records were obtained in Hefei, China, during January 2013 to December 2016. The findings showed that PM_2.5, PM₁₀, SO₂, NO₂, and O₃ exposures were positively correlated with the risk of birth defects. Maternal exposure to PM_2.5 and SO₂ during the 4th to 13th gestational weeks was observed to have a significant association with the risk of birth defects, with the maximum effect in the 7th or 8th week for PM_2.5 and the maximum effect in the 7th week for SO₂. The positively significant exposure windows were the 4th to 14th weeks for PM₁₀, the 4th to 12th weeks for NO₂, and the 26th to 35th weeks for O₃, respectively. The strongest associations were observed in the 8th week for PM₁₀, the 7th week for NO₂, and in the 31st or 32nd week for O_3. The findings of this study demonstrate that air pollutants increase the risk of birth defects among women during pregnancy in Hefei, China, which provide evidence for improving the health of pregnant women and neonates in developing countries, and uncovered potential opportunities to reduce or prevent birth defects by proactive measures during pregnancy.

First trimester exposure to ambient gaseous air pollutants and risk of orofacial clefts: a case-control study in Changsha, China

Background

A growing body of studies have investigated the association between air pollution exposure during early pregnancy and the risk of orofacial clefts, but these studies put more emphasis on particulate matter and reported inconsistent results, while research on the independent effects of gaseous air pollutants on orofacial clefts has been quite inadequate, especially in China.

Methods

A case–control study was conducted in Changsha, China from 2015 to 2018. A total of 446 cases and 4460 controls were included in the study. Daily concentrations of CO, NO₂, SO₂, O₃, PM_2.5 and PM₁₀ during the first trimester of pregnancy were assigned to each subject using the nearest monitoring station method. Multivariate logistic regression models were applied to evaluate the associations of monthly average exposure to gaseous air pollutants with orofacial clefts and its subtypes before and after adjusting for particulate matter. Variance inflation factors (VIFs) were used to determine if the effects of gaseous air pollutants could be independent of particulate matter.

Results

Increase in CO, NO₂ and SO₂ significantly increased the risk of cleft lip with or without cleft palate (CL/P) in all months during the first trimester of pregnancy, with aORs ranging from 1.39 to 1.48, from 1.35 to 1.61 and from 1.22 to 1.35, respectively. The risk of cleft palate only (CPO) increased with increasing NO₂ exposure levels in the first trimester of pregnancy, with aORs ranging from 1.60 to 1.66. These effects sustained and even exacerbated after adjusting for particulate matter. No significant effect of O₃ was observed.

Conclusions

Our study suggested that maternal exposure to CO, NO₂, and SO₂ during the first trimester of pregnancy might contribute to the development of orofacial clefts, and the associations were potentially independent of particulate matter.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01876-7.

Meta-analyses of maternal exposure to atmospheric particulate matter and risk of congenital anomalies in offspring

Congenital anomalies are the main causes of infant death and disability. Previous studies have suggested that maternal exposure to particulate matter is related to congenital malformation. However, the conclusions of this study remain controversial. Hence, meta-analyses were performed to assess the relationship between maternal exposure to particulate matter and the risk of congenital anomalies. The Medline, Embase, and Web of Science databases were systemically searched from inception until August 2020 to find articles related to birth defects and particulate matter. The pooled risk estimated for the combination of pollution outcomes was calculated for each study by performing fixed effects or random effects models. The existence of heterogeneity and publication bias in relevant studies was also examined. Thirty studies were included in the analysis. A statistically increased summary risk valuation was found. PM₁₀ exposure was associated with an increased risk of congenital heart disease, neural tube defects, and cleft lip with or without cleft palate (OR per 10 μg/m³ = 1.05, 95% CI, 1.03-1.07; OR per 10 μg/m³ = 1.04, 95% CI, 1.01-1.06; OR per 10 μg/m³ = 1.03, 95% CI, 1.01-1.06). Maternal exposure to particulate matter might be associated with an increased risk of congenital anomalies. Our results indicate the dangers of particulate matter exposure on fetal development and the importance of protection against exposure to such particles during pregnancy. The schematic representation of the association between maternal exposure to PM_2.5/PM₁₀ and congenital anomalies in offspring, and geographic distribution of the included reports in the meta-analyses.

Maternal exposure to sulfur dioxide and the risk of oral clefts in Liaoning Province, China: a population-based case-control study

There is limited and equivocal epidemiological evidence relating to the association between maternal sulfur dioxide (SO₂) exposure and the risk of oral clefts (OCs) in offspring. We performed a population-based case-control study in Liaoning province to evaluate aforementioned relationship during 3 months before conception, the first trimester of pregnancy, and their single months. The study involved 3086 patients with OCs and 7950 controls. Data relating to SO₂ concentration was acquired from air monitoring stations throughout the study period. We used a multivariable logistic regression model to evaluate the association between exposure to SO₂ and the risk of OCs during the exposure windows. Maternal SO₂ exposure was positively related to OCs during the 3 months before conception (odds ratio = 1.38, 95% confidence interval: 1.15-1.65; P for trend < 0.01). Positive relationships were obtained from the first and second months before conception and the first month of pregnancy. Thus, our research reflects a relationship between SO₂ exposure and the risk of OCs. Future studies are now required to verify the association between SO₂ exposure and OCs during pregnancy and indicate the most relevant vulnerable exposure time windows.

The association between ambient air pollution and birth defects in five major ethnic groups in Liuzhou, China

Background

Studies suggest that exposure to ambient air pollution during pregnancy may be associated with increased risks of birth defects (BDs), but conclusions have been inconsistent. This study describes the ethnic distribution of major BDs and examines the relationship between air pollution and BDs among different ethnic groups in Liuzhou city, China.

Methods

Surveillance data of infants born in 114 registered hospitals in Liuzhou in 2019 were analyzed to determine the epidemiology of BDs across five major ethnic groups.

Concentrations of six air pollutants (PM2.5, PM10, SO2, CO, NO2, O3) were obtained from the Liuzhou Environmental Protection Bureau. Logistic regression was used to examine the associations between ambient air pollution exposure and risk of BDs.

Results

Among 32,549 infants, 635 infants had BDs, yielding a prevalence of 19.5 per 1000 perinatal infants. Dong ethnic group had the highest prevalence of BDs (2.59%), followed by Yao (2.57%), Miao (2.35%), Zhuang (2.07%), and Han (1.75%). Relative to the Han ethnic group, infants from Zhuang, Miao, Yao and Dong groups had lower risks of congenital heart disease, polydactyly, and hypospadias. The Zhuang ethnic group had higher risks of severe thalassemia, cleft lip and/or palate, and syndactyls. Overall BDs were positively correlated with air pollutants PM₁₀ (aOR =1.14, 95% CI:1.12 ~ 2.43; aOR =1.51, 95% CI:1.13 ~ 2.03 for per 10μg/mg3 increment) and CO (aOR =1.36, 95% CI:1.14 ~ 2.48; aOR =1.75, 95% CI:1.02 ~ 3.61 for every 1 mg /m3 increment) in second and third month of pregnancy. SO₂ was also significantly associated with BDs in the second month before the pregnancy (aOR = 1.31; 95% CI: 1.20 ~ 3.22) and third month of pregnancy (aOR =1.75; 95% CI:1.02 ~ 3.61). Congenital heart disease, polydactyl, cleft lip and/or palate were also significantly associated with PM₁₀, SO₂ and CO exposures. However, no significant association was found between birth defects and O₃, PM_2.5 and NO₂ exposures (P > 0.05).

Conclusion

This study provides a comprehensive description of ethnic differences in BDs in Southwest China and broadens the evidence of the association between air pollution exposure during gestation and BDs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02687-z.

Maternal exposure to ambient SO2 and risk of polydactyly and syndactyly: a population-based case-control study in Liaoning Province, China

Evidence links exposure to maternal sulfur dioxide (SO₂) and the risk of limb defects have been inconsistent. To investigate associations between SO₂ exposure during preconception and the first trimester and risks of polydactyly and syndactyly. The study population was acquired from the Maternal and Child Health Certificate Registry of Liaoning Province between 2010 to 2015, and consisted of 2605 polydactyly, 595 syndactyly cases, and 7950 controls. Ambient air pollutants levels were retrieved from air quality monitoring stations. We used multivariable logistic regression model to assess the adjusted odds ratios (ORs) and 95% confidence intervals (CIs). We found that exposure to increased SO₂ concentrations was associated with polydactyly during both the 3 months preconception (OR_{Q4 vs. Q1} = 3.76; 95% CI 2.61, 5.42; per 10 μg/m³ increment: OR = 1.07; 95% CI 1.04, 1.10) and the first trimester (OR_{Q4 vs. Q1} = 2.03; 95% CI 1.41, 2.92; per 10 μg/m³ increment: OR = 1.07; 95% CI 1.03, 1.11). However, we only observed increased risk for syndactyly in the analysis of high vs. low quartiles (three months preconception: OR_{Q4 vs. Q1} = 3.72; 95% CI 2.05, 6.75; first trimester: OR_{Q4 vs. Q1} = 1.98; 95% CI 1.11, 3.51). Most results of analyses based on single-month exposure window generally showed similar positive associations. Additionally, these findings were broadly consistent across subgroups and sensitivity analyses. Maternal SO₂ exposure increase the risk of polydactyly and syndactyly.

Maternal exposure to ambient levels of sulfur dioxide and risk of neural tube defects in 14 cities in Liaoning province, China: a population-based case-control study

Epidemiological studies on the association of sulfur dioxide (SO₂) with neural tube defects (NTDs) are lacking. The purpose of this study was to assess the aforementioned association through a population-based case-control study. This study involved 1457 NTDs cases and 7950 randomly selected healthy infants born in 14 cities in Liaoning province between 2010 and 2015. Ambient SO₂ levels were acquired from 75 monitoring stations. The exposure assessment was based on the mean concentration of all stations in mother's residential city. We used logistic regression models to assess the associations. In multivariable models adjusted for the confounding variables selected based on the 10 percent change-in-estimate method, we found that maternal SO₂ exposure was positively associated with an increased risk of NTDs during the first month after conception (per 10 μg/m³ increase: adjusted odds ratio [aOR] = 1.02, 95% confidence interval [CI]: 1.00-1.04; highest versus lowest quartile: aOR = 2.55, 95% CI: 1.97-3.31) and the second month after conception (per 10 μg/m³ increase: aOR = 1.02, 95% CI: 1.00-1.04; highest versus lowest quartile: aOR=2.31, 95% CI: 1.77-3.00). For other exposure windows, positive associations also emerged in high- versus low-exposure analyses, except for the third month before conception; however, we could not further confirm significant findings from the continuous exposure analyses. Our study provides a new evidence that SO₂ exposure may increase the risk of NTDs.

Birth defects and unconventional natural gas developments in Texas, 1999-2011

Unconventional natural gas developments (UNGD) may release air and water pollutants into the environment, potentially increasing the risk of birth defects. We conducted a case-control study evaluating 52,955 cases with birth defects and 642,399 controls born between 1999 and 2011 to investigate the relationship between UNGD exposure and the risk of gastroschisis, congenital heart defects (CHD), neural tube defects (NTDs), and orofacial clefts in Texas. We calculated UNGD densities (number of UNGDs per area) within 1, 3, and 7.5 km of maternal address at birth and categorized exposure by density tertiles. For CHD subtypes with large case numbers, we also performed time-stratified analyses to examine temporal trends. We calculated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for the association with UNGD exposure, accounting for maternal characteristics and neighborhood factors. We also included a bivariable smooth of geocoded maternal location in an additive model to account for unmeasured spatially varying risk factors. Positive associations were observed between the highest tertile of UNGD density within 1 km of maternal address and risk of anencephaly (aOR: 2.44, 95% CI: 1.55, 3.86), spina bifida (aOR: 2.09, 95% CI: 1.47, 2.99), gastroschisis among older mothers (aOR: 3.19, 95% CI: 1.77, 5.73), aortic valve stenosis (aOR: 1.90, 95% CI: 1.33, 2.71), hypoplastic left heart syndrome (aOR: 2.00, 95% CI: 1.39, 2.86), and pulmonary valve atresia or stenosis (aOR: 1.36, 95% CI: 1.10, 1.66). For CHD subtypes, results did not differ substantially by distance from maternal address or when residual confounding was considered, except for atrial septal defects. We did not observe associations with orofacial clefts. Our results suggest that UNGDs were associated with some CHDs and possibly NTDs. In addition, we identified temporal trends and observed presence of spatial residual confounding for some CHDs.

Associations between weekly air pollution exposure and congenital heart disease

BACKGROUND

The topic of congenital heart diseases (CHDs) has attracted more and more attentions. Accumulating evidence suggests that exposure to air pollutants during pregnancy is associated with CHDs, yet the results are inconsistent and study about weekly exposure is few. Our study evaluated the association between weekly air pollution and CHDs in Hefei, China.

MATERIALS AND METHODS

Daily CHDs admission data were obtained from eight hospitals in Hefei from October 2015 to September 2017. Meteorological data and air quality were collected from China Meteorological Data Network. Distributed lag nonlinear model (DLNM) considering both the lag effect of exposure factors and the nonlinear relationship of exposure-reaction was used to assess the effect of weekly air pollutants exposure on CHDs admission.

RESULTS

During the study period, totally 47,046 cases of perinatal infants were recruited, and the incidence of CHDs was 9.71 per thousand. The findings showed PM_2.5, PM₁₀, SO₂ and NO₂ significantly increased the risk of CHDs. Each 10 μg/m³ increase in PM_2.5 during gestational weeks 20-26 increased the risk of CHDs. The susceptibility windows of PM₁₀ (weeks 0-2 and weeks 25-29 of pregnancy), SO₂ (weeks 8-16 and weeks 29-38) and NO₂ (week 40), while the strongest effects of these 4 pollutants on CHDs were observed in week 22 (RR = 1.034, 95% CI: 1.007-1.062), week 0 (RR = 1.081, 95% CI: 1.02-1.146), week 37 (RR = 1.528, 95% CI: 1.085-2.153) and week 40 (RR = 1.171, 95% CI: 1.006-1.364), respectively.

CONCLUSIONS

Air pollutants (SO₂, NO₂, PM₁₀, and PM_2.5) exposure could increase the risk of CHDs, while the most crucial susceptibility windows for the exposure were mainly in the second and third trimesters. Boys seemed to be more sensitive to air pollution. Our study contributes to the knowledge of the association between maternal exposure to air pollution and CHDs, but the associations need to be verified by further studies.

Gestational exposures to outdoor air pollutants in relation to low birth weight: A retrospective observational study

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO₂ were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO₂ in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02-3.58 for increment of interquartile range (18.5 μg/m³); p-value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO₂ during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO₂ exposures could be greater during early periods than during later periods of gestation.

Association between prenatal exposure to ambient particulate matter and risk of hypospadias in offspring: A systematic review and meta-analysis

BACKGROUND

Epidemiological studies on whether prenatal exposure to PM_2.5, PM_2.5-10, and PM₁₀ increases the risk of hypospadias are limited and the results are inconsistent.

OBJECTIVES

We conducted this systematic review and meta-analysis to evaluate these associations.

METHODS

Relevant studies were identified by searching the PubMed and Embase databases up to the end of February 2020. Observational studies that investigated the relationships between prenatal exposure to PM₁₀, PM_2.5, and PM_2.5-10 and the risk of hypospadias in offspring were eligible for the review. The risk of bias was evaluated using the Newcastle-Ottawa scale. Random-effects models were used to estimate pooled relative risks (RRs) and 95% confidence intervals (CIs) for the associations.

RESULTS

Nine studies (two cohort and seven case-control studies) with a total of 2806 hypospadias cases were included. Eight studies were at low risk of bias and only one study was at high risk of bias. Five studies reported the association between per interquartile range increase in PM_2.5 exposure within the first trimester and the risk of hypospadias. The pooled RR was 1.17 (95% CI: 1.00, 1.36). Two studies reported the per interquartile range increase in PM_2.5 exposure during 1 month before pregnancy associated with the risk of hypospadias, with a pooled RR of 1.25 (95% CI: 1.03, 1.51). No association was observed between PM_2.5-10 and PM₁₀ exposure during pregnancy and the risk of hypospadias in offspring.

CONCLUSION

This study suggested a modest association between prenatal PM_2.5 exposure during 1 month before pregnancy or within the first trimester and the risk of hypospadias in offspring. Further large-scale cohort studies are required to verify this association.

Maternal exposure to ambient particulate matter 10 μm or less in diameter before and after pregnancy, and anencephaly risk: A population-based case-control study in China

BACKGROUND

There is no epidemiological evidence on the effects of maternal exposure to ambient particulate matter 10 μm or less in diameter (PM₁₀) and anencephaly risk in offspring.

METHODS

We conducted a population-based case-control study in Liaoning Province, China. The case group consisted of 663 cases with anencephaly and the control group consisted of 7950 healthy infants from the Maternal and Child Health Certificate Registry of Liaoning Province that were born between 2010 and 2015. Daily PM₁₀ concentrations were obtained from 77 monitoring stations located within the study area. A multivariable logistic regression model was established to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Maternal PM₁₀ exposure was significantly associated with an increased risk of anencephaly at three months before conception (highest versus lowest tertile: OR = 1.74, 95% CI: 1.29-2.34; per 10 μg/m³ increment: OR = 1.13, 95% CI: 1.06-1.20) and three months after conception (highest versus lowest tertile: OR = 1.93, 95% CI: 1.44-2.60; per 10 μg/m³ increment: OR = 1.01, 95% CI: 0.95-1.08). The evaluation of shorter exposure windows revealed similar associations for PM₁₀ exposure from the third month before pregnancy to the third month after pregnancy.

CONCLUSIONS

Maternal PM₁₀ exposure is positively associated with anencephaly risk during the critical period of neural system development.

Road impact in a protected area with rich biodiversity: the case of the Sebitoli road in Kibale National Park, Uganda

While road network expansion is crucial for economic development, it can cause a notable disturbance of fauna, especially in protected area in terms of habitat fragmentation, risk of collision, and also indirect threat such as pollution. In this study, we monitored the 4.6-km long tarmac road crossing the Kibale National Park in Uganda, home to a rich variety of wild species including the endangered chimpanzees. We evaluated the effects of collisions and pollution, as well as the impact of the renovation process in terms of disturbance and the mitigation measures deployed. This survey reports the death of 24 wild animals killed by cars, including two chimpanzees. The atmospheric concentrations of O₃, NO₂, SO₂, and BTEX did not exceed recommended limits. More than 5000 plastic bottles were collected along the road within 4 months, and for the first time, the presence of BPA and BPS was detected in the hairs of wild chimpanzees. The road bisecting the Kibale National Park poses a high danger in terms of traffic and an underestimated risk related to plastic pollution. Measures (signpost, speed bumps) should be urgently deployed to decrease the risk posed by the renovated road for emblematic species such as chimpanzees, which are crucial for tourism and economy in Uganda.

Association between maternal exposure to PM10 and polydactyly and syndactyly: A population-based case-control study in Liaoning province, China

BACKGROUND

The number of studies on air pollution with birth defects as the primary outcome has increased dramatically over the past two decades, but the potential role of specific air pollutants in congenital limb anomalies remains unclear.

OBJECTIVES

To evaluate associations between preconception and first-trimester PM₁₀ exposure and polydactyly and syndactyly in a population-based case-control study.

METHODS

Polydactyly cases (n = 2605), syndactyly cases (n = 595), and controls without any birth defects (n = 7950) born between 2010 and 2015 were selected from the Maternal and Child Health Certificate Registry of Liaoning Province. The monthly mean PM₁₀ concentrations were obtained from 75 air monitoring stations, and the exposure assessment was based on the mean concentration of all stations in mother's residential city. A multivariable logistic regression model was constructed to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

RESULTS

PM₁₀ exposure was positively associated with the risks of polydactyly (preconception: aOR_{T3 vs. T1} = 1.95, 95% CI 1.56-2.45, aOR = 1.06, 95% CI 1.01-1.10 [per 10-μg/m³ increment]; first-trimester: aOR_{T3 vs. T1} = 2.51, 95% CI 2.00-3.15) and syndactyly (preconception: aOR_{T3 vs. T1} = 2.86, 95% CI 1.98-4.13, aOR = 1.11, 95% CI 1.03-1.20 [per 10-μg/m³ increment]; first-trimester: aOR_{T3 vs. T1} = 3.10, 95% CI 2.11-4.56). Analyses based on single month exposure windows basically showed similar positive associations. Additionally, these findings were robust in sensitivity analyses and broadly consistent across subgroups.

CONCLUSION

Our study suggest that preconception and first-trimester PM₁₀ exposures are related to increased risks of polydactyly and syndactyly.

Maternal preconception and first trimester exposure to PM10 and the risk of oral clefts in offspring: a population-based, case-control study

BACKGROUND

Current literature describes limited and controversial evidence on the associations between maternal preconception and first trimester exposure to particulate matter with a diameter ≤10 µm (PM₁₀) and the risk of oral cleft (OC).

METHODS

We conducted a case-control study involving 3086 OC cases and 7950 controls, registered in the Maternal and Child Health Certificate Registry in Liaoning Province between 2010 and 2015. PM₁₀ concentrations were obtained from the Environment Protection Bureau. The exposure windows included the 3 months before pregnancy, the first trimester and the individual months. Unconditional logistic regression model was performed to estimate the OR and 95% CI for the association between PM₁₀ exposure and the risk of OC, cleft lip only (CLO), cleft palate only (CPO), and cleft lip and palate (CLP).

RESULTS

Maternal PM₁₀ exposure was positively associated with an increased risk for OC during the 3 months preconception (per 10 µg/m³ increment: OR=1.04, 95% CI 1.01 to 1.07; highest vs lowest quartile: OR=1.23, 95% CI 1.04 to 1.45) and the first trimester (per 10 µg/m³ increment: OR=1.05, 95% CI 1.02 to 1.08; highest vs lowest quartile: OR=1.37, 95% CI 1.15 to 1.64). Analyses based on individual months presented similar positive associations, particularly in the second month of pregnancy (OR=1.77, 95% CI 1.51 to 2.09) for highest versus lowest quartile. In the subtype analysis, stronger associations were observed for CLO, whereas there was negligible evidence for CPO and CLP. Sensitivity analyses using propensity score matching generated similar findings.

CONCLUSIONS

Our study provides evidence that PM₁₀ exposure during the 3 months preconception and the first trimester increases the risk of OC.

Maternal air pollution exposure associated with risk of congenital heart defect in pre-pregnancy overweighted women

OBJECTIVES

Prenatal exposure to air pollutant has been associated with congenital heart defect (CHD). However, no study has investigated this effect in pre-pregnancy overweighted women. This study aimed to evaluate gestational exposure to particulate pollutant (PM_2.5) and gaseous air pollutants (O₃ and NO₂) on the risk of CHD, and explore the potential effect modifiers including maternal age, pre-pregnancy BMI and pregestational diseases.

METHODS

In this birth cohort study, a total of 63,213 pregnant women in Foshan, China were initially recruited and followed from their first hospital visit for pregnancy to delivery during 2015-2019. CHD cases were confirmed by the records in hospital- and population- based birth defect surveillance systems. Air pollutant exposures were estimated by the daily concentrations measured in air monitoring stations in each participant's residential county. Mixed-effects regression models, adjusted for potential confounding factors were applied to estimate the associations between air pollutant and CHD during the first three months of the pregnancy.

RESULTS

A total of 985 (1.6%) newborns were identified as CHD cases. For each 10 μg/m³ increase in ambient O₃ during the 1st month, the OR values for CHD were 1.03 (95% CI: 0.94, 1.13) in pre-pregnancy normal weighted women and 1.24 (95% CI: 1.01, 1.53) in pre-pregnancy overweighted women. For each 10 μg/m³ increase in NO₂ during the 3rd month, the OR values for CHD were 1.09 (95% CI: 1.01, 1.18) in pre-pregnancy normal weighted women and 1.27 (95% CI: 1.07, 1.51) in pre-pregnancy overweighted women. No significant associations were found between PM_2.5 exposure and CHD in our analysis.

CONCLUSIONS

This study demonstrates that gaseous air pollutants (O₃ and NO₂) exposure during the cardiac embryogenesis period is associated with an increased risk of CHD, particularly for pre-pregnancy overweighted women.

The correlation between methylenetetrahydrofolate reductase gene 677C > T polymorphism and fetal congenital defects: A meta-analysis

Objective To investigate the correlation between the methylenetetrahydrofolate reductase (MTHFR) gene 677C> T polymorphism and fetal congenital defects.

Method Original studies relevant to the MTHFR gene 677C>T single nucleotide polymorphism and fetal congenital defects were systematically searched in the electronic databases of Medline, EMBSE and China National Knowledge Infrastructure (CNKI). All relevant publications were screened for inclusion in the present work. The correlation between the MTHFR gene 677C > T single nucleotide polymorphism and the occurrence of fetal congenital defects was expressed as an odds ratio (OR) and its 95% confidence interval (95% CI). Publication bias was assessed by Begg’s funnel plot and Egger’s line regression test.

Results Nineteen case-control studies were ultimately included in the present meta-analysis. The pooled results indicated that the general risk of fetal congenital defects was significantly elevated in subjects with the 677T allele of the MTHFR gene in dominant (OR=1.07,95%CI:1.03-1.12, P<0.05), homozygous (OR=1.17,95%CI:1.06-1.30, P<0.05) and recessive genetic models (OR=1.16,95%CI:1.03-1.31, P<0.05) through the random effect method. However, significant publication bias was identified upon pooling the individual data and evaluating the correlation.

Conclusion According to the present evidence, the MTHFR gene 677C>T single nucleotide polymorphism is correlated with poor pregnancy outcomes, and subjects with the T allele have an increased risk of developing general fetal congenital defects.