Prenatal Ambient Air Pollutants Influence Fetal Blood Flow and Shunting to the Brain in the Third Trimester

Abstract

Background: Prenatal exposure to air pollutants has been associated with numerous adverse fetal outcomes.Objectives: We tested whether air pollutants affect umbilical venous perfusion of the fetal liver and shunting of blood from liver to brain in the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) pregnancy cohort. We hypothesized prenatal air pollution exposure contributes to an adverse intrauterine environment and alters fetal blood flow by shunting less blood to the liver and more to the brain. Methods: Daily estimates of ambient air pollutants NO2, PM10, PM2.5 and O3 were spatially interpolated at each participant’s residence. Prenatal average exposures were calculated from the date of conception to the date of ultrasound. Doppler ultrasound measurements were performed between 30-34 weeks’ gestation for 102 participants by a certified obstetrics sonographer to determine the proportion of umbilical vein (UVf) blood flowing to the ductus venosus (DVf) or the fetal liver (FLf) in ml/min. Shunting was calculated as the proportion of blood flow, DVf/ UVf. Linear regression models were used to evaluate the associations between single pollutants and UVf, DVf, FLf, and DVf/ UVf adjusting for covariates.Results: Mean maternal age was 28 (6) years and gestational age at study visit was 31.7 (1.1) weeks. PM10 and PM2.5 were significantly associated with DVf (β = 9.4 and 5.1, p < 0.0001, p=0.04 for a 1 SD change in pollutant) and with shunting (β = 3.3 and 0.20, p < 0.0001, p=0.02). Daily 8hr maximum O3 and 24hr average O3 were associated with DVf (β = 7.1, 5.8, p =0.003, 0.02) and 8hr maximum O3 with shunting (β =1.7, p= 0.04).Conclusions: Prenatal air pollutant exposure was associated with blood flow in the ductus venosus and shunting of blood from liver to brain, the long-term consequences of which remain unknown.