Intrauterine Inflammation and Maternal Exposure to Ambient PM2.5 during Preconception and Specific Periods of Pregnancy: The Boston Birth Cohort

BACKGROUND: Prenatal exposure to ambient PM2.5, (i.e., fine particulate matter, aerodynamic diameter <= 2.5 mu m) has been associated with preterm birth and low birth weight. The association between prenatal PM2.5 exposure and intrauterine inflammation (IUI), an important risk factor for preterm birth and neurodevelopmental outcomes, has not been evaluated. OBJECTIVES: We aimed to investigate the association between maternal exposure to PM2.5 and IUI in the Boston Birth Cohort, a predominantly urban low-income minority population. METHODS: This analysis included 5,059 mother-infant pairs in the Boston Birth Cohort. IUI was assessed based on intrapartum fever and placenta pathology. PM2.5 exposure was assigned using data from the U.S. EPA's Air Quality System. Odds ratios (OR) and 95% confidence intervals (CI) quantified the association of maternal PM2.5 exposure during preconception and various periods of pregnancy with IUI. RESULTS: Comparing the highest with the lowest PM2.5 exposure quartiles, the multi-adjusted association with IUI was significant for all exposure periods considered, including 3 months before conception (OR = 1.52; 95% CI: 1.22, 1.89), first trimester (OR = 1.93; 95% CI: 1.55, 2.40), second trimester (OR= 1.67; 95% CI: 1.35, 2.08), third trimester (OR= 1.53; 95% CI: 1.24, 1.90), and whole pregnancy (OR = 1.92; 95% CI: 1.55, 2.37). CONCLUSIONS: Despite relatively low exposures, our results suggest a monotonic positive relationship between PM2.5 exposure during preconception and pregnancy and IUI. IUI may be a sensitive biomarker for assessing early biological effect of PM2.5 exposure on the developing fetus.