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 out-comes. Some epidemiologic studies explored the association between maternal PM2.5 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 PM2.5 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 PM2.5 at 1 km spatial resolution was estimated by gap-filling model. Gener-alized 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 PM2.5 exposure with outcomes, respectively.Results: Significant associations were found between acute PM2.5 exposures (per interquartile range increase) and the risk of preterm PROM (OR = 1.11; 95 % CI: 1.03, 1.19 for PM2.5 on delivery day; OR = 1.10; 95 % CI: 1.02, 1.18 for PM2.5 1 day before delivery) but not for term PROM. An interquartile range increase in PM2.5 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 PM2.5 exposure. Conclusion: Our findings suggest that both acute and chronic maternal exposures to ambient PM2.5 during pregnancy are risk factors for PROM.

Automated summary

This study found that both acute and chronic maternal exposure to ambient PM2.5 during pregnancy are risk factors for PROM, with a stronger association found between PM2.5 exposure and preterm PROM. Women who are less educated, obese, or give birth in a cold season appear to be more sensitive to ambient PM2.5 exposure.