Prenatal air pollution exposure and placental vasculature development among participants of the UPSIDE cohort study

Air pollution exposure during pregnancy has been associated with reduced fetal growth and birth weight, but mechanisms mediating this association are not well understood.

We examined whether pregnancy air pollution exposures were associated with altered placental vascularization.

We studied pregnant women (N = 163) from the UPSIDE cohort study, part of the Environmental Influences on Child Health Outcomes (ECHO) Study. Using placenta photographs taken at birth (gestational weeks 37-42), we derived seventeen chorionic plate surface vessel outcomes in 7 groups: arterial area, arterial branches, arterial arc length, arterial endpoint distance to perimeter, arterial branch angle, arterial tortuosity, and artery-vein distances. Distributed lag nonlinear models were used to determine if/when gestational week mean PM_2.5 and NO₂ concentrations were associated with the seventeen chorionic plate surface vessel outcomes.

Placental measures were more strongly associated with weekly NO₂ than PM_2.5. Higher early-pregnancy NO₂ concentrations were associated with lower measures of the arterial area and arterial endpoint distance to perimeter groups, and greater measures of the arterial tortuosity group (e.g., each 9-ppb increase in NO₂ concentration in gestational weeks 0-12 was associated with lower arterial surface area; cumulative β = -1.46 cm²; 95 % CI = -2.73, -0.19). Higher NO₂ in late-pregnancy was associated with increased measures of the arterial area, arc length, tortuosity, and artery-vein distances groups, and decreased measures of the arterial branch group (e.g., 9-ppb increases in NO₂ concentration in gestational weeks 18-37 were associated with lower numbers of arterial generations; cumulative β = -1.30 generations; 95 % CI = -2.22, -0.38).

Residential traffic pollution exposure in early-pregnancy was associated with altered chorionic surface arterial vasculature, potentially leading to worse perfusion, while late-pregnancy positive associations may represent a compensatory response.