Mother-level random effect in the association between PM2.5 and fetal growth: A population-based pregnancy cohort

Prenatal PM2.5 exposure increases the risk of adverse pregnancy outcomes: evidence from meta-analysis of cohort studies

Adverse pregnancy outcomes (APOs) are a significant cause of fetal death. A wide range of maternal psychological, social, and environmental factors may contribute to these outcomes. Mounting epidemiological studies have indicated that PM2.5 may result in these unfavorable consequences. Previously published meta-analyses have been updated and extended. Cohort studies were searched from three databases (up to July 24, 2023), and their quality was assessed by Newcastle-Ottawa Scale (NOS). Publication bias was examined by Egger's test and funnel plot. Despite a large number of studies showing similar results, the inconsistencies between these findings require careful generalization before concluding. This meta-analysis included 67 cohort studies from 20 countries, and the findings revealed that maternal PM2.5 exposure and five APOs were correlated significantly throughout pregnancy: preterm birth (PTB) (RR = 1.05; 95% CI: 1.03, 1.07); low birth weight (LBW) (RR = 1.02; 95% CI: 1.01, 1.04); small for gestational age (SGA) (RR = 1.03; 95% CI: 1.01, 1.04); stillbirth (RR = 1.24; 95% CI: 1.06, 1.45); and change in birthweight (weight change = -6.82 g; 95% CI: -11.39, -2.25). A positive association was found between APOs and PM2.5 exposure in this meta-analysis, and the degree of increased risk of APOs varied due to different gestation periods. Therefore, it is necessary to protect pregnant women at specific times.

Association between ambient particulate matter and preterm birth stratified by temperature: A population-based pregnancy cohort study

A growing body of literature reports associations between exposure to particulate matter with aerodynamic diameters ≤2.5 μm (PM2.5) and 2.5-10 μm (PM10-2.5) during pregnancy and preterm birth (PTB). However, the role of ambient temperature in PM-PTB associations was rarely investigated. In Israel, we used Maccabi Healthcare Services data to establish a population-based cohort of 381,265 singleton births reaching 24-42 weeks' gestation and birth weight of 500-5000 g (2004-2015). Daily PM and ambient temperature predictions from a satellite-based spatiotemporal model, at a 1 × 1 km spatial resolution, were linked to the date of birth and maternal residence. Mixed effects Cox regression models, adjusted for covariates, with a random intercept at the mother level were used to assess associations between mean exposure during pregnancy and PTB. We found that exposure to PM2.5 was positively associated with PTB when the average exposure during pregnancy was either low (first quintile) or high (fifth quintile), compared to exposure in the 2nd-4th quintiles, with hazard ratios (HRs) 1.18 (95% confidence interval [CI], 1.13-1.24) and 1.07 (95% CI, 1.02-1.12), respectively. The results revealed effect modification of temperature. For mothers exposed to low (below median) average temperature during pregnancy, HRs of PTB were 0.93 (95% CI, 0.87-1.00) and 1.21 (95% CI, 1.14-1.29) for the first and fifth PM2.5 quintiles, respectively, when compared to the 2nd-4th quintiles. However, a reverse trend was indicated for high-temperature pregnancies, where the corresponding HRs were 1.48 (95% CI, 1.39-1.58) and 0.92, (95% CI, 0.96-0.98). In conclusion, consideration of climatic factors can provide new insights into the risk of PTB as a result of exposure to PM2.5 during pregnancy.

Maternal exposure to particulate matter early in pregnancy and congenital anomalies in offspring: Analysis of concentration-response relationships in a population-based cohort with follow-up throughout childhood

Studies have suggested an association between particulate matter (PM) air pollution and certain congenital anomalies (CAs). However, most studies assumed a linear concentration-response relation and were based on anomalies that were ascertained at birth or up to 1 year of age. We investigated associations between exposures to PM during the first trimester of pregnancy and CAs in 9 organ systems using birth and childhood follow-up data from a leading health care provider in Israel. We conducted a retrospective population-based cohort study among 396,334 births, 2004-2015. Daily PM data at a 1 × 1 km spatial grid were obtained from a satellite-derived prediction models and were linked to the mothers' residential addresses at birth. Adjusted odds ratios (ORs) were estimated with logistic regression models using exposure levels as either continuous or categorical variables. We captured 57,638 isolated CAs with estimated prevalence of 96 and 136 anomalies per 1000 births in the first year of life and by age 6 years, respectively. Analysis of continuous PM with diameter < 2.5 μm (PM_2.5) indicated a supra-linear relation with anomalies in the circulatory, respiratory, digestive, genital and integument systems (79 % of CAs). The slope of the concentration-response function was positive and steepest for PM_2.5 lower than the median concentration (21.5 μg/m³) and had a less steep or negative slope at higher levels. Similar trends were observed for PM_2.5 quartiles. For example, for cardiac anomalies, the ORs were 1.09 (95 % confidence interval: 1.02, 1.15), 1.04 (0.98, 1.10) and 1.00 (0.94, 1.07) for births in the second, third and fourth quartiles, respectively, when compared to the first quartile. In sum, this study adds new evidence for adverse effects of air pollution on neonatal health even with low-level air pollution. Information on late diagnosis of children with anomalies is important in evaluating the burden of disease.

Decreased birth weight after prenatal exposure to wildfires on the eastern coast of Korea in 2000

OBJECTIVES

In April 2000, a series of wildfires occurred simultaneously in five adjacent small cities located on the eastern coast of Korea. These wildfires burned approximately 23,794 hectares of forestland over several days. We investigated the effects of prenatal exposure to the by-products generated by wildfire disasters on birth weight.

METHODS

Birth weight data were obtained for 1999-2001 from the birth registration database of the Korean National Statistical Office and matched with the zip code and exposed/unexposed pregnancy week for days of the wildfires. Generalized linear models were then used to assess the associations between birth weight and exposure to wildfires after adjusting for fetal sex, gestational age, parity, maternal age, maternal education, paternal education, and average exposed atmospheric temperature.

RESULTS

Compared with unexposed pregnancies before and after the wildfires, mean birth weight decreased by 41.4 g (95% confidence interval [CI], -72.4 to -10.4) after wildfire exposure during the first trimester, 23.2 g (95% CI, -59.3 to 13.0) for exposure during the second trimester, and 27.0 g (95% CI, -63.8 to 9.8) during the third trimester. In the adjusted model for infants exposed in utero during any trimester, the mean birth weight decreased by 32.5 g (95% CI, -53.2 to -11.7).

CONCLUSIONS

We observed a 1% reduction in birth weight after wildfire exposure. Thus, exposure to by-products generated during a wildfire disaster during pregnancy may slow fetal growth and cause developmental delays.

Association of ambient air pollution exposure with low birth weight

Increasing evidence has shown that exposure to air pollution is linked to adverse birth outcomes, but the results are not consistent. This study was performed on a subset of participants from the UK Biobank between 2006 and 2010. The land use regression (LUR) model was constructed to calculate the concentrations of particulate matter (PM2.5, PM2.5-10 and PM10), nitrogen oxides (NOx), and nitrogen dioxide (NO2). Binary logistic/multivariate linear regression models were applied to explore the potential linear relationships between air pollution exposure and newborn low birth weight (LBW) or BW. The Cochran-Armitage trend test was used to explore the possible association between the air pollution level and LBW. A restricted cubic spline (RCS) transformation of exposure variables was applied to visualize the relation of air pollutants to BW. Exposure to air pollutants, especially PM2.5 and PM10, was positively associated with LBW, and the odds ratios (ORs) and 95% confidence intervals (CIs) for each 10-μg/m3 increase in PM2.5 and PM10 were 1.25 ([1.03, 1.51], P = 0.025) and 1.12 ([1.02, 1.24], P = 0.021), respectively. A negative correlation was observed between the BW and PM2.5 (-0.05 [-0.08, -0.02], P = 0.001), PM10 (-0.03 [-0.05, -0.02], P < 0.001), PM2.5-10 (-0.04 [-0.07, -0.01], P < 0.001) and NOx (0.00 [0.00, 0.00], P = 0.021). Additionally, the BW changed dramatically up to a specific point (PM2.5 for 10.74 μg/m3, Pnonlinearity = 0.004; PM10 for 16.06 μg/m3, Pnonlinearity = 0.004; NO2 for 25.58 μg/m3, Pnonlinearity <0.001; and NOx for 39.88 μg/m3, Pnonlinearity <0.001), subsequently becoming relatively stable. PM2.5 and PM10 exposure were positively associated with LBW, and a negative correlation was observed between PM2.5, PM2.5-10, PM10 and NOx and BW.