RESUMO
BACKGROUND: The synergic effects of thermal inversion (TI) and particulate matter with an aerodynamic diameter ≤1 µm (PM1) exposure and incidence of small for gestational age (SGA) was not clear. OBJECTIVE: We aimed to explore the independent effects of prenatal TI and PM1 exposure on incidence of SGA and their potential interactive effects. METHODS: A total of 27,990 pregnant women who delivered in Wuhan Children's Hospital from 2017 to 2020 were included. The daily mean concentration of PM1 was obtained from ChinaHighAirPollutants (CHAP) and matched with the residential address of each woman. Data on TI was derived from National Aeronautics and Space Administration (NASA). The independent effects of PM1 and TI exposures on SGA in each gestational week were estimated by the distributed lag model (DLM) nested in Cox regression model, and the potential interactive effects of PM1 and TI on SGA were investigated by adapting the relative excess risk due to interaction (RERI) index. RESULTS: Per 10 µg/m3 increase in PM1 was associated with an increase in the risk of SGA at 1-3 and 17-23 gestational weeks, with the strongest effect at the first gestational week (HR = 1.043, 95%CI: 1.008, 1.078). Significant links between one day increase of TI and SGA were found at the 1-4 and 13-23 gestational weeks and the largest effects were observed at the 17th gestational week (HR = 1.018, 95%CI: 1.009, 1.027). Synergistic effects of PM1 and TI on SGA were detected in the 20th gestational week, with RERI of 0.208 (95%CI: 0.033,0.383). IMPACT STATEMENT: Both prebirth PM1 and TI exposure were significantly associated with SGA. Simultaneous exposure to PM1 and TI might have synergistic effect on SGA. The second trimester seems to be a sensitive window of environmental and air pollution exposure.