Interactive effects of ambient air pollution and sunshine duration on the risk of intrahepatic cholestasis of pregnancy

Introduction: While the associations among ambient pollutants and various pregnancy complications are well documented, the effect of ambient pollutants on intrahepatic cholestasis of pregnancy (ICP) has not been examined. This study aimed to explore the effects of ambient pollutants and sunshine duration on ICP.Methods: The study enrolled 169,971 pregnant women who delivered between 2015 and 2020 in two hospitals. The associations between ICP and exposure to ambient pollutants and sunshine duration, averaged throughout different periods (including the 3 months before conception, 1st trimester and 2nd trimester), were estimated using a generalized linear model. The interaction effects of ambient pollutants and sunshine duration on ICP were estimated.Results: The fitted curves for ICP incidence were similar to the temporal trends of PM2.5, PM10, SO2, CO and NO2 but not that of O-3. The risk of ICP was significantly elevated following a 10-mu g/m(3) increase in PM2.5 (aOR [adjusted odds ratio] = 1.057, 95% CI [confidence interval]: 1.017-1.099) and PM10 (aOR = 1.043, 95% CI: 1.013-1.074) and a 1-h decrease in sunshine duration (aOR = 1.039, 95% CI: 1.011-1.068) during the 3 months before conception. In the second trimester, a 1-mu g/m(3) increase in the concentration of SO2 was associated with an increased risk of ICP (aOR = 1.011, 95% CI: 1.001-1.021). Increased concentrations of PM2.5 and PM10 had interactive effects with reduced sunshine duration during the 3 months before conception on increasing the risk of ICP.Conclusions: Exposure to PM2.5 and PM10 during the 3 months before conception and exposure to SO2 in the second trimester were associated with an increased ICP risk. Reduced sunshine duration had an interactive effect with increased concentrations of PM2.5 and PM10 during the 3 months before conception on the occurrence of ICP.