Exposure-lag response of fine particulate matter on intrauterine fetal death: an analysis using a distributed lag non-linear model in Linxia Hui Autonomous Prefecture, China.

The results of studies on intrauterine fetal death (IUFD) caused by exposure to fine particulate matter (PM) during pregnancy are inconsistent. Further exploration of the dose-response relationship and exposure window is required. We aimed to provide a reference for policy formulation by estimating the exposure-lag relationship of PM on IUFD and looking for sensitive exposure windows. IUFD data was obtained from China Children Under 5 Death Surveillance Network in Linxia Hui Autonomous Prefecture from 2016 to 2020. Air pollution data and temperature data were obtained from ambient air monitoring stations and China Meteorological Data Network, respectively. The moving average is used to describe the trend and seasonality of PM exposure; the distributed lag non-linear model (DLNM) is used to estimate the exposure-lag effect; the sandwich estimators are used to correct the variance-covariance matrix; and the model selected by Akaike's Information Criterion (AIC) finally adjusts gender, temperature, and district. About 180,622 infants were enrolled in the study, including 952 IUFDs (5.27‰). The median of PM exposure is 34.08 μg/m. There is an exposure-lag effect of PM on IUFD approximate to a wavy shape; the concentration with effect is 40-90 μg/m; and the sensitive lag time is 1, 2, 3, 8, 9, and 10 months. The maximum RR value of the exposure-lag effect of PM on IUFD is 1.61 [95% CI 1.19, 2.19], in which the concentration of PM is 62 μg/m, and the lag month is 9 months. In the case of less than 6 months lag, the maximum RR value of the exposure-lag effect of PM on IUFD is 1.43 [95% CI 1.24, 1.67], in which the concentration of PM is 73 μg/m, and the lag month is 3 months. Exposure to PM concentrations above 40 μg/m may increase the risk of IUFD, especially in the first and third trimesters.