BACKGROUND: Health disparities have persisted in severe maternal morbidity (SMM), an event in which a woman nearly dies from a complication during pregnancy, with limited data on environmental risk factors.
OBJECTIVE: To examine the association between prenatal exposure to high and low ambient temperatures and SMM during critical windows of pregnancy for a birth cohort in the Southeastern United States.
METHODS: This retrospective, population-based birth cohort included hospital deliveries from 1999 to 2017 (570,660 women, 921,444 deliveries). Daily average temperatures at the county-scale were merged with delivery discharge records and days of exposure to very hot and very cold were estimated over the following critical windows: preconception, and first, second, and third trimesters (T1-T3). Generalized estimating equations with multivariable Poisson models examined the association between temperature extremes and SMM for each critical window.
RESULTS: Women exposed to a low compared to a high number of cold days during the first and third trimesters were 1.11 (CI: 1.03, 1.20) and 1.30 (CI: 1.20, 1.42) times more likely to experience SMM, respectively. Compared to the no exposure group, women exposed to a high number of very hot temperatures during preconception were 1.09 (95%CI:1.02,1.18) more likely to experience SMM. Sustained exposure to a high or moderate-intensity heat wave during the summer months was associated with a 45% or 39% increase in SMM risk during T2, respectively. Pregnant populations residing in rural locations were more sensitive to cold exposure in T3. Women exposed to a high number of very hot days in T2 compared to no exposure were 20% more likely to experience preterm SMM.
SIGNIFICANCE: Findings suggest that maternal exposure to hot or cold temperature extremes around the time or during pregnancy may be a contributing environmental risk factor for SMM. More attention should be focused on prenatal counseling in pregnant populations around the risk of thermal extremes.