Risk of de novo hypertensive disorders of pregnancy after exposure to PM1 and PM2.5 from preconception to delivery: a Chinese birth cohort study (Preprint)

BACKGROUND Particulate matter (PM) is detrimental to the respiratory and circulatory system. However, no study was found evaluating the lag effects of weekly exposure to fine PM from preconception to delivery on the risk of hypertensive disorders of pregnancy (HDP). OBJECTIVE To investigate the lag effect windows of PMs on the risk of HDP in week scale. METHODS De novo HDP and normotensive pregnant women in this study were from the Peking University Retrospective Birth Cohort in Tongzhou based on the hospital information system. Meteorological data and fine PM exposure were predicted by satellite remote sensing data based on maternal residential address. De novo HDP group consisted of the pregnant women who diagnosed with gestational hypertension or preeclampsia. Fine PM was defined as PM2.5 and PM1. The gestational period of participants was from preconception (-12th gestational week) to delivery (before 42nd gestational week). The distributed lag nonlinear model (DLNM) was nested in Cox regression model to evaluate the lag effects of weekly PM exposure on de novo HDP hazard by controlling the nonlinear relationship of exposure-reaction. Stratified analyzes by employment status (employment, unemployment), education level (higher education, lower education), and parity (primiparity, multiparity) were performed. RESULTS A total of 22570 pregnant women (mean age, 29.1 years) were included in this study between 2013 and 2017, and the prevalence of de novo HDP was 6.7%. The findings showed that PM1 and PM2.5 were significantly associated with the elevated hazard of HDP. Exposure to PM1 during the -5th – 6th gestational weeks increased the hazard of HDP. The significant lag effect of PM2.5 was from -1st to 6th gestational weeks. The strongest lag effects of PM1 and PM2.5 on de novo HDP were observed in week 2 and week 6 (HR = 1.024, 95% CI: 1.007-1.042; HR = 1.007, 95% CI: 1.000-1.015, per 10 μg/m3 increase). Stratified analyzes indicated that pregnant women with employment, low education, and primiparity were more vulnerable to PM exposure for de novo HDP. CONCLUSIONS Exposure to PM1 and PM2.5 was associated with the risk of de novo HDP. The significant lag windows were between the pre-conceptional period and the first trimester. Women with employment, lower education level or primiparity were more vulnerable to the effects of PMs exposure and should be paid more attention in early prevention of de novo HDP.