Prenatal Exposure to Ambient Air Pollution, Gestational Weight Gain, and Offspring Birth Weight

Abstract

Background: Insufficient or excessive gestational weight gain (GWG) impacts the progression and outcomes of pregnancy with consequences on mothers and their offspring over the life course. Environmental factors, such as ambient air pollution, have been associated with weight change in animal models and non-pregnant populations. However, association of ambient air pollution with GWG and subsequent birth outcomes is not well investigated. We investigated associations of particulate matter with a diameter of less than 2.5 micrometers (PM2.5) with GWG and infant birth weight. Methods: The present study was conducted among a subset of participants from the Omega Study, a prospective pregnancy cohort. Exposure to PM2.5 was predicted for participants based on their residential address using a national spatiotemporal model. Separate multivariable linear regression models, adjusted for relevant confounders, were used to estimate associations of trimester-specific and monthly (corresponding to months in pregnancy) PM2.5 exposures with early (<20 weeks gestation), late (≥20 weeks gestation), and total GWG, as well as associations of trimester-specific and monthly PM2.5 exposures with infant birth weight. To examine whether pre-pregnancy BMI (ppBMI) and infant sex modified the associations, stratified models and interaction terms were used. Results: Average age of the participants was 32.87 years, and average PM2.5 exposure during the first, second, and third trimester were 5.10 μg/m3, 20.23 μg/m3, and 14.68 μg/m3, respectively. There was no evidence of an overall association between trimester-specific and monthly PM2.5 exposure and early, late, or total GWG. However, higher third trimester PM2.5 exposure was associated with higher late (0.40 kg per 5 μg/m3 PM2.5 exposure; 95% CI: 0.12, 0.67) and total (0.35 kg per 5 μg/m3 PM2.5 exposure; 95% CI: 0.01, 0.70) GWG among participants with normal ppBMI. Similar associations were not observed among the overweight/obese group for third trimester PM2.5 exposure and late (0.09 kg; 95% CI: -0.32, 0.49) and total (-0.06 kg; 95%CI: -0.57, 0.46) GWG (p-value for interaction > 0.05). Higher second month PM2.5 exposure was associated with lower early (-0.70 kg; 95% CI: -1.22, -0.18), late (-0.84 kg; 95% CI: -1.54, -0.14), and total (-1.70 kg; 95% CI: -2.57, -0.82) GWG among participants with overweight/obese ppBMI. However, among participants with normal ppBMI, there was no evidence of an association between second month PM2.5 exposure and early (0.10 kg; 95% CI: -0.28, 0.48), late (-0.16 kg; 95% CI: -0.67, 0.35), and total (-0.01 kg; 95% CI: -0.66, 0.64) GWG. Terms for interaction were significant for second month PM2.5 exposure and early and total GWG (p-values = 0.01 and p-value < 0.01, respectively). Higher third trimester PM2.5 exposure was associated with higher birth weight (102.75 g per 5 μg/m3 PM2.5 exposure; 95% CI: 70.65, 134.85), though higher fourth month PM2.5 exposure was associated with lower birth weight (-66.34 g per 5 μg/m3 PM2.5 exposure; 95% CI: -126.61, -6.08). Interactions of PM2.5 with ppBMI or infant sex on birth weight were not statistically significant. Conclusions: Associations of PM2.5 with GWG vary by exposure window and ppBMI while associations of PM2.5 with birth weight potentially vary by exposure window. Future studies that examine these associations among diverse populations and studies that evaluate underlying biological mechanisms are needed.