Intrauterine inflammation and maternal exposure to ambient pm_2.5 during preconception and specific periods of pregnancy: The boston birth cohort

Background: Prenatal exposure to ambient PM_2.5, (i.e., fine particulate matter, aerodynamic diameter ≤ 2.5 μm) has been associated with preterm birth and low birth weight. The association between prenatal PM_2.5 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 PM_2.5 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. PM_2.5 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 PM_2.5 exposure during preconception and various periods of pregnancy with IUI. Results: Comparing the highest with the lowest PM_2.5 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 PM_2.5 exposure during preconception and pregnancy and IUI. IUI may be a sensitive biomarker for assessing early biological effect of PM_2.5 exposure on the developing fetus.