Prenatal heat stress and predicted postpartum cardiovascular disease risk: a longitudinal cohort study

Heat stress has been implicated as a risk factor for cardiovascular disease (CVD). Wet bulb globe temperature (WBGT) is considered a more physiologically relevant measure of heat stress than temperature alone, accounting for direct sunlight, relative humidity, solar radiation, and wind speed. Pregnant individuals may be particularly vulnerable to heat stress due to physiological changes in thermoregulation. Pregnancy may serve as a sensitive period influencing future health, but it is unknown if prenatal heat stress impacts postpartum cardiovascular health. We examined associations between prenatal, residential WBGT exposure and postpartum Pathobiologic Determinants of Atherosclerosis in Youth (PDAY) risk scores, which predict future atherosclerosis. Among 193 participants from the Maternal and Developmental Risks from Environmental and Social Stressors pregnancy cohort, annual postpartum PDAY scores were calculated across 6 years postpartum, using age, non-high-density lipoprotein cholesterol, high-density lipoprotein cholesterol, hypertension, obesity, and hyperglycemia from in-person questionnaires and biomarker samples. We used hierarchical generalized additive models (GAMs) to examine associations between pregnancy average and trimester-specific WBGT and postpartum PDAY scores. Effect modification by prenatal psychosocial stressors, urban heat island index (UHII), and climate vulnerability index (CVI) was assessed through stratification. Distributed lag non-linear models (DLNM) with mixed effects assessed weekly associations. Models were adjusted for maternal age at consent, pre-pregnancy body mass index, household income, maternal education, race/ethnicity, and conception season. Model fit indices indicated a nonlinear relationship between average prenatal WBGT and postpartum PDAY scores, with a positive association emerging at temperatures above 19 °C, though confidence intervals were wide. We were unable to observe evidence of associations with trimester-specific WBGT, sensitive windows of exposure, or effect modification by psychosocial stressors, UHII, or CVI. Our data suggested an association at pregnancy average WBGT greater than 19 °C with postpartum cardiometabolic health risk scores, however sparsity at temperature extremes limited our conclusions. The relatively limited exposure variability in our study region and small sample size may have limited our ability to observe more robust associations.