Air Pollution Exposure and Markers of Placental Growth and Function: The Generation R Study

BACKGROUND Air pollution exposure during pregnancy might affect placental growth and function, perhaps leading to pregnancy complications. OBJECTIVE We prospectively evaluated the associations of maternal air pollution exposure with markers of placental growth and function among 7,801 pregnant women in the Netherlands. METHODS We estimated levels of particulate matter ≤ 10 µm in aerodynamic diameter (PM10) and nitrogen dioxide (NO2) at the home address for different periods during pregnancy using dispersion modeling techniques. Pro- and anti-angiogenic factors [placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1), respectively] were measured in first- and second-trimester maternal blood and in fetal cord blood samples at delivery. Pulsatility index of the uterine and umbilical arteries was measured by Doppler ultrasound in second and third trimester, and notching was assessed in third trimester. Placenta weight and birth weight were obtained from medical records. RESULTS Higher PM10 and NO2 exposure levels were associated with lower second-trimester maternal sFlt-1 and PlGF levels. PM10 and NO2 exposures averaged over total pregnancy were associated with higher sFlt-1 and lower PlGF levels in fetal cord blood, consistent with an anti-angiogenic state. PM10 and NO2 exposures were not consistently associated with second- or third-trimester placental resistance indices. NO2 exposure was associated with third-trimester notching (odds ratio 1.33; 95% CI: 0.99, 1.78 per 10-µg/m3 increase in the prior 2 months). PM10 and NO2 exposures were associated with lower placenta weight (-11.8 g; 95% CI: -20.9, -2.7, and -10.7 g; 95% CI: -19.0, -2.4, respectively, per 10-µg/m3 increase in the prior 2 months), but not with placenta to birth weight ratio. CONCLUSIONS Our results suggest that maternal air pollution exposure may influence markers of placental growth and function. Future studies are needed to confirm these findings and explore the maternal and fetal consequences.