Association of ambient fine particulate matter and its chemical constituents with preterm birth: a population-based cohort study with sibling comparison design.

Effects of ambient fine particulate matter (PM) chemical constituents on preterm birth (PTB) are inconclusive. We performed a sibling-matched cohort study to explore the association between PM constituents and the risk of PTB. Changes in PM and the constituents (ΔPM ΔOC, ΔBC, ΔSO, ΔNH, ΔNO) were calculated as the value at a follow-up pregnancy minus exposures in prior pregnancy. A fixed-effect regression model was used to determine the association of the within-group variation in PM total mass and constituents with PTB risk. Gestational age differences within matched siblings were also treated as outcomes. A total of 62,334 sibling pairs were analyzed. We observed that each 10 μg/m increase in ΔPM in first, second, and third trimester were not statistically significant associated with the risk of PTB, but shortened gestational age was observed, with -0.009 week (95% CI: -0.013, -0.005), -0.005 (95% CI: -0.008, -0.002), -0.012 (95%CI: -0.015, -0.008) and -0.019 week (95% CI: -0.026, -0.012) decrease in first, second, third and whole pregnancy. Our findings indicate that increase in ambient PM constituents was associated with a shorten gestational age. This study added a novel cohort evidence for the association of changes of PM components with gestational age.