Risk for preeclampsia following exposure to PM_2.5 during pregnancy

Background: Previous findings concerning the risk for preeclampsia following exposure to particulate matter are inconclusive. Methods: We used data from all singleton pregnancies of women insured by the “Clalit health services” (CHS) maintenance organization in southern Israel that resulted in delivery or perinatal mortality at Soroka Medical Center (SMC). Daily PM_2.5 concentrations were estimated by a hybrid satellite-based model at one-squared kilometer spatial resolution. We used Cox proportional hazard models coupled with distributed lag models to examine the association between the mean exposure to PM_2.5 in every gestational week and the diagnosis of preeclampsia, adjusting for maternal age, parity, year of birth, season of birth and socio-economic status. Hazard Ratios (HR) and 95% Confidence Intervals (CI) were calculated for individual gestational weeks and for cumulative exposure until the 25th gestational week. Results: A total of 133,197 pregnancies ended at SMC during the study period, of which 68,126 (51.1%) were Jewish and 65,071 (48.9%) were Bedouin. For pregnancies of Jewish women, exposure to PM_2.5 from the 7th until the 14st gestational week was significantly associated with preeclampsia (maximal HR = 1.06; 95%CI: 1.01 – 1.11 during the 10th gestational week per 10 μg/m³ increase in PM_2.5). Cumulative exposure to PM_2.5 during the first 25th gestational weeks was also significantly associated with preeclampsia (HR = 2.08; 95%CI: 1.10 – 3.94 per 10 μg/m³ increase in PM_2.5). We observed no association for pregnancies of Bedouin women. Conclusions: Exposure to PM_2.5 between the 7th and the 14st gestational weeks was associated with preeclampsia among Jewish women but not among Bedouin women.