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

Prenatal PM2.5 Exposure and Its Association with Low Birth Weight: A Systematic Review and Meta-Analysis

Exposure to PM2.5 while pregnant is associated with negative effects on low birth weight (LBW). This study employed a systematic review and meta-analysis to investigate the impact of PM2.5 exposure during pregnancy on LBW. A search of databases such as Scopus, ScienceDirect, and PubMed identified thirteen appropriate studies. This study used a random-effects model to calculate pooled odds ratios (ORs) and 95% confidence intervals (CIs) for each trimester. The findings revealed a significant relationship between PM2.5 exposure and LBW in both the first and second trimesters (OR 1.05, 95% CI 1.00-1.09, p < 0.001). There was no significant difference between trimesters (p = 0.704). The results emphasize the persistent influence of PM2.5 on fetal development throughout all stages of pregnancy. Reducing air pollution is critical for improving pregnancy outcomes and decreasing the incidence of LBW. Further study is needed to improve exposure assessments and investigate the underlying biological pathways.

Maternal physical activity, sitting, and risk of non-cardiac birth defects

BACKGROUND

The relationship between maternal physical activity (PA)/sitting and birth defects is largely unexplored. We examined whether pre-pregnancy PA/sitting were associated with having a pregnancy affected by a birth defect.

METHODS

We used data from two United States population-based case-control studies: 2008-2011 deliveries from the National Birth Defects Prevention Study (NBDPS; 9 states) and 2014-2018 deliveries from the Birth Defects Study To Evaluate Pregnancy exposureS (BD-STEPS; 7 states). Cases with one of 12 non-cardiac birth defects (n = 3798) were identified through population-based registries. Controls (n = 2682) were live-born infants without major birth defects randomly sampled using vital/hospital records. Mothers self-reported pre-pregnancy PA/sitting. Unconditional logistic regression models estimated associations between PA/sitting categories and the 12 birth defects.

RESULTS

Mothers engaging in pre-pregnancy PA was associated with a reduced odds of five (spina bifida, cleft palate, anorectal atresia, hypospadias, transverse limb deficiency) and a higher odds of two (anencephaly, gastroschisis) birth defects. Mothers spending less time sitting in pre-pregnancy was associated with a reduced odds of two (anorectal atresia, hypospadias) and a higher odds of one (cleft lip with or without cleft palate) birth defect.

CONCLUSIONS

Reasonable next steps include replication of these findings, improved exposure assessment, and elucidation of biologic mechanisms.

IMPACT

Using data from two population-based case-control studies, we found that mothers engaging in different types of physical activity in the 3 months before pregnancy had an infant with a reduced odds of five and a higher odds of two birth defects. Mothers spending less time sitting in the 3 months before pregnancy had an infant with a reduced odds of two and a higher odds of one birth defect. Clarification and confirmation from additional studies are needed using more precise exposure measures, distinguishing occupational from leisure-time physical activity, and elucidation of mechanisms supporting these associations.

Incidence of cleft lip and palate, and epidemiology of perinatal deaths related to cleft lip and palate in Hunan Province, China, 2016-2020

This study aimed to analyze the epidemiological characteristics of cleft lip and/or palate (CL/P) and CL/P-related perinatal deaths, provide some information for intervention programs to reduce the incidence of CL/P and provide clues for future researchers. Data were obtained from the Birth Defects Surveillance System in Hunan Province, China, 2016-2020. Incidences of CL/P [number of cases per 1000 fetuses (births and deaths at 28 weeks of gestation and beyond)] with 95% confidence intervals (CI) were calculated by residence, gender, maternal age, year, and major types [cleft lip only (CL), cleft palate only (CP), and cleft lip with palate (CLP)]. Crude odds ratios (ORs) were calculated to examine the association of each maternal characteristic with CL/P. Pearson chi-square tests (χ²) were used to examine the association of each maternal characteristic with CL/P-related perinatal deaths. A total of 847,755 fetuses were registered, and 14,459 birth defects were identified, including 685 CL/P (accounted for 4.74% of all birth defects). CL, CP, and CLP accounted for 24.67% (169 cases), 36.79% (252 cases), and 38.54% (264 cases) of all CL/P, respectively. The incidence of CL/P was 0.81‰ (95%CI 0.75-0.87). The incidence of CL was 0.20‰ (95%CI 0.17-0.23) (169 cases), of CP was 0.30‰ (95%CI 0.26-0.33) (252 cases), and of CLP was 0.31‰ (95%CI 0.27-0.35) (264 cases). CL was more common in males than females (0.24‰ vs. 0.15‰, OR = 1.62, 95%CI 1.18-2.22). CP was more common in urban than rural (0.36‰ vs. 0.25‰, OR = 1.43, 95%CI 1.12-1.83), and less common in males than females (0.22‰ vs. 0.38‰, OR = 0.59, 95%CI 0.46-0.75). CLP was more common in males than females (0.35‰ vs. 0.26‰, OR = 1.36, 95%CI 1.06-1.74). Compared to mothers 25-29 years old, mothers < 20 years old were risk factors for CLP (OR = 3.62, 95%CI 2.07-6.33) and CL/P (OR = 1.80, 95%CI 1.13-2.86), and mothers ≥ 35 years old was a risk factor for CLP (OR = 1.43, 95%CI 1.01-2.02). CL/P-related perinatal deaths accounted for 24.96% (171/685) of all CL/P, of which 90.64% (155/171) were terminations of pregnancy. Rural residents, low income, low maternal age, and early prenatal diagnosis are risk factors for perinatal death. In conclusion, we found that CP was more common in urban areas and females, CL and CLP were more common in males, and CL/P was more common in mothers < 20 or ≥ 35 years old. In addition, most CL/P-related perinatal deaths were terminations of pregnancy. CL/P-related perinatal deaths were more common in rural areas, and the proportion of CL/P-related perinatal deaths decreased with the increase in maternal age, parity, and per-capita annual income. Several mechanisms have been proposed to explain these phenomena. Our study is the first systematic research on CL/P and CL/P-related perinatal deaths based on birth defects surveillance. It is significant for intervention programs to prevent CL/P and CL/P-related perinatal deaths. As well, more epidemiological characteristics of CL/P (such as the location of CL/P) and approaches to reduce CL/P-related perinatal deaths need to be studied in the future.

Effects of maternal urban particulate matter SRM 1648a exposure on birth outcomes and offspring growth in mice

The association between exposure to particulate matter (PM) during pregnancy and abnormal birth outcomes is still inconclusive. This study aims to provide more evidence for this public health concern by investigating birth outcomes and the growth of offspring in mice exposed to PM during pregnancy. C57BL/6 J pregnant mice were exposed to PM via nasal drip at three doses or solvent control. The dam weight gain was recorded during pregnancy. The number of pups, pup weight, and placental weight were recorded at embryonic day 18.5 (E18.5) necropsy. For mice that gave birth naturally, we calculated the gestation length and measured the body weight of offspring once a week from the 1st to the 6th week after birth. The results showed that there were no significant differences in maternal body weight gain, conception rate, pregnancy duration, and litter size among different groups. There were no significant differences in fetal weight, placental weight, and fetal/placental weight ratio at E18.5. Weight gain in offspring was reduced after birth. The average body weight of offspring in the high-dose group was significantly lower than that in the control group at weeks 5 in female pups. There were no significant differences in the body weight of male offspring among groups from 1st to the 6th. Together, our study indicated that maternal exposure to PM did not significantly impact birth outcomes of C57BL/6 J mice but affected growth trajectories in offspring after birth in a dose- and fetal sex-dependent manner.

The short-term effects of air pollution exposure on preterm births in Chongqing, China: 2015-2020

Accumulating evidence suggested that the risk of preterm births (PTBs) following prenatal exposure to air pollution was inconclusive. The aim of this study is to investigate the relationship between air pollution exposure in the days before delivery and PTB and assess the threshold effect of short-term prenatal exposure to air pollution on PTB. This study collected data including meteorological factors, air pollutants, and information in Birth Certificate System from 9 districts during 2015-2020 in Chongqing, China. Generalized additive models (GAMs) with the distributed lag non-linear models were conducted to assess the acute impact of air pollutants on the daily counts of PTB, after controlling for potential confounding factors. We observed that PM2.5 was related to increased occurrence of PTB on lag 0-3 and lag 10-21 days, with the strongest on the first day (RR = 1.017, 95%CI: 1.000-1.034) and then decreasing. The thresholds of PM2.5 for lag 1-7 and 1-30 days were 100 μg/m3 and 50 μg/m3, respectively. The lag effect of PM10 on PTB was very similar to that of PM2.5. In addition, the lagged and cumulative exposure of SO2 and NO2 was also associated with the increased risk of PTB. The lag relative risk and cumulative relative risk of CO exposure were the strongest, with a maximum RR at lag 0 (RR = 1.044, 95%CI: 1.018, 1.069). Importantly, the exposure-response curve of CO showed that RR increased rapidly when the concentration exceeded 1000 μg/m3. This study indicated significant associations between air pollution and PTB. The relative risk decreases with day lag, while the cumulative effect increases. Thus, pregnant women should understand the risk of air pollution and try to avoid high concentration exposure.

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.

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.