Associations of perinatal exposure to PM2.5 with gestational weight gain and offspring birth weight

PM2.5 have been associated with weight change in animal models and non-pregnant populations. Evidence of associations between PM2.5 and gestational weight gain (GWG), an important determinant of course and outcomes of pregnancy, and subsequent birth outcomes is limited. The study was conducted among a subset of participants from the Omega Study, a prospective pregnancy cohort. Exposure to PM2.5 (μg/m3) was ascertained for participants (N = 855) based on their residential address using a validated national spatiotemporal model. Adjusted multivariable linear regression models were used to estimate associations of trimester-specific and pregnancy-month PM2.5 exposures with early (<20 weeks gestation), late (≥20 weeks gestation), and total GWG and infant birth weight. Stratified models and product terms were used to examine whether pre-pregnancy BMI (ppBMI) and infant sex modified the associations. Average monthly PM2.5 exposure during the first, second, and third trimesters were 7.3 μg/m3, 7.9 μg/m3, and 7.7 μg/m3, respectively. Higher third trimester PM2.5 exposure was associated with higher late (0.40 kg per 5 μg/m (McDowell et al., 2018); 95%CI: 0.12, 0.67) and total (0.35 kg; 95%CI: 0.01, 0.70) GWG among participants with normal ppBMI. 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. Product terms between PM2.5 and ppBMI were significant for second month PM2.5 exposure and early (p-value = 0.01) and total GWG (p-value<0.01). Higher third trimester PM2.5 exposure was associated with higher birth weight, though higher fourth month PM2.5 exposure was associated with lower birth weight, particularly among those with normal ppBMI and male infants. 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, ppBMI and infant sex. Further exploration of associations between PM2.5 and maternal/child health outcomes are needed.