Effects of maternal exposure to particulate matter during pregnancy on the birth weight of offspring: A negative control exposures study

The impact of prenatal particulate matter (PM) on birth weight in full-term children remains unclear. Our study aimed to explore the causal effect of maternal PM exposure during pregnancy on birth weight of full-term offspring. Subjects, from the birth cohort in Jinan City, were born at full term, singleton, and with normal birth weight. The daily exposure concentration for each mother during pregnancy and the mirror period was assessed by the inverse distance weighted method. The generalized linear models and negative control exposures method were used to evaluate causality between them through evaluating known and unknown confounding. Finally, 4114 subjects were included in this study. In the entire pregnancy, for a 10 mu g/m(3) PM increase, the reduction of the birth weight was 17.36 g (95%CI: -30.96 g, -3.77 g) for PM10 and 28.92 g (95%CI: -56.96 g, -0.89 g) for PM2.5 after adjusting known confounding, and it was 26.93 g (95%CI: -44.82 g, -9.03 g) for PM10 and 34.41 g (95%CI: -68.28 g, -0.54 g) for PM2.5 after assessing unknown confounding. Additionally, in the first and third trimester, they were 24.13 g (95%CI: -36.41 g, -11.84 g) and 11.60 g (95%CI: -22.75 g, -0.35 g) for PM10, and 30.53 g (95%CI: -55.15 g, -5.91 g) and 29.47 g (95%CI: -54.98 g, -3.96 g) for PM2.5, respectively. Consequently, there was a causal effect of maternal exposure to PM during pregnancy on birth weight loss of full-term offspring. The first and third trimester may be the critical windows.