Maternal exposure to air pollution and fetoplacental Doppler markers during pregnancy

Maternal exposure to air pollution has been associated with a wide range of adverse perinatal outcomes; however, the evidence on its influence on the placenta has remained limited. We studied the association of maternal exposure to air pollution with fetoplacental Doppler markers in a cohort of pregnant women recruited in three tertiary hospitals and their primary care centers in Barcelona, Spain (2018- 2021). Maternal exposure to nitrogen dioxide (NO₂), black carbon (BC), and particulate matter <2.5 μm (PM_2.5) was assessed at home, workplace, commuting route, and all these microenvironments combined using different modelling techniques: land use regression (LUR), dispersion (DM), and Hybrid LUR-DM (HM) models. Doppler examination of the Uterine artery (UtA) mean pulsatility index (PI) was assessed in the first, second, and third trimester of pregnancy, while the umbilical artery (UA) PI, middle cerebral artery (MCA) PI, and cerebroplacental ratio (CPR) were examined in the third trimester. Mixed effects linear regression models with recruiting hospital as the random effect were used to estimate associations, controlled for relevant covariates. Higher maternal exposure to NO₂ and BC was consistently associated with increased UtA mean PI, particularly for home and total exposure estimates by all three exposure models, while PM_2.5 showed similar associations in some exposure models (DM). We also observed a significant association between home NO₂ exposure and lower CPR, suggesting subtle fetal hemodynamic adaptation to impaired placental function. Overall, our findings provide evidence that maternal exposure to ambient air pollution may adversely affect uteroplacental vascular function. Further prospective studies are needed to confirm these associations and assess their clinical relevance for maternal and fetal outcomes.