UCLA

Prenatal exposures to ambient particulate matter (PM2.5) from traffic may generate oxidative stress, and thus contribute to adverse birth outcomes including preterm birth (PTB) and term low birth weight (TLBW), but little is known about the effects of exposure to specific constituents of PM2.5 or mechanisms that contribute to these outcomes. Furthermore, numerous studies have reported the effects of maternal diet on adverse birth outcomes, but few population-based studies evaluated maternal dietary patterns and placental growth. In this dissertation, we investigated health effects of prenatal exposures to PM2.5 from brake and tire wear, and how the maternal diet affects placental growth during pregnancy.First, in a birth cohort of 285,614 singletons born in Los Angeles County, California during 2017-2019, we estimated increased risks for PTB and TLBW per interquartile range (IQR) exposure increment of metals and oxidative potential metrics that were robust to adjustment for PM2.5 mass. Second, we investigated whether these PM2.5 constituents affect levels of oxidative stress biomarkers (malondialdehyde (MDA), 8-hydroxy-2’-deoxyguanosine (8-OHdG)) using urine samples collected up to three times during pregnancy in a cohort of pregnant women recruited from antenatal clinics at the University of California Los Angeles (UCLA). 8-OHdG concentrations in mid-pregnancy increased per IQR increase in PM2.5 mass and black carbon. The brake wear marker (barium) and the oxidative potential metrics were associated with increased urinary MDA concentration in early pregnancy, but 95% CIs included the null. Last, using the same cohort recruited from UCLA, we found placental volume in mid-pregnancy was associated with a higher score of Healthy Eating Index-2015 (≥ median), and a higher placenta weight at delivery was associated with a higher score of Alternate Mediterranean Diet (≥ median). Our results indicate that reduction of PM2.5 mass only may not be sufficient to protect the most vulnerable pregnant women from adverse effects due to traffic source exposures. Our findings provide novel insights into potential biological mechanism of PM2.5 exposure related health effect among pregnant women. Moreover, our study suggests that placentation and adverse pregnancy outcomes can be addressed by nutritional measures and interventions in early to mid-pregnancy.