Acute and chronic maternal exposure to fine particulate matter and prelabor rupture of the fetal membranes: A nation-wide survey in China.

Background: Prelabor rupture of the fetal membranes (PROM) is a major contributor to adverse perinatal outcomes. Some epidemiologic studies explored the association between maternal PM exposure and PROM but failed to treat the labor induction and prelabor cesarean section as censored observations.

Objective: We aimed to evaluated whether acute and chronic maternal ambient PM exposure may increase the risk of PROM in China.

Methods: This study was based on the China Labor and Delivery Survey, a nationwide multicenter investigation. Included in the current analysis were 45,879 singleton spontaneous births in 96 hospitals in mainland China from 2015 to 2017. Outcomes were PROM, preterm PROM (<37 weeks' gestation) and term PROM (≥37 weeks' gestation). Daily concentration of PM at 1 km spatial resolution was estimated by gap-filling model. Generalized linear mixed model and mixed effects Cox model were applied to assess the associations of acute (from 0 to 4 days before delivery) and chronic (average gestational and trimester-specific) ambient PM exposure with outcomes, respectively.

Results: Significant associations were found between acute PM exposures (per interquartile range increase) and the risk of preterm PROM (OR = 1.11; 95 % CI: 1.03, 1.19 for PM on delivery day; OR = 1.10; 95 % CI: 1.02, 1.18 for PM 1 day before delivery) but not for term PROM. An interquartile range increase in PM during the second trimester was associated with elevated risks of PROM (HR = 1.14; 95 % CI: 1.07, 1.22), preterm PROM (HR = 1.22; 95 % CI: 1.02, 1.45) and term PROM (HR = 1.13; 95 % CI: 1.06, 1.22), respectively. Women who were less educated, obese, or gave birth in a cold season appeared to be more sensitive to ambient PM exposure.

Conclusion: Our findings suggest that both acute and chronic maternal exposures to ambient PM during pregnancy are risk factors for PROM.