Extreme Heat Exposure Enhanced the Associations Between Prepregnancy Weight and the Hypertensive Disorders of...

Prepregnancy overweight or obesity may increase cardiovascular risk, but whether extreme heat intensifies its association with hypertensive disorders of pregnancy (HDPs) or endothelial dysfunction (ED) is unclear.

In this population-based cohort of 7820 pregnant women, prepregnancy body mass index and HDPs were obtained from hospital records. Ambient temperature data were sourced from the National Centers for Environmental Information. Plasma endothelial biomarkers (VCAM-1 [vascular cell adhesion molecule-1], ICAM-1 [intercellular adhesion molecule-1], E-selectin) were measured at 24 to 28 weeks' gestation, and latent profile analysis defined ED. Generalized linear and restricted cubic spline models assessed associations between prepregnancy overweight or obesity and HDPs or ED across extreme heat exposure groups.

Overall, 6.6% of women developed HDPs and 9.4% were classified with ED. Prepregnancy overweight or obesity was associated with higher risks of HDPs (odds ratio [OR], 2.68 [95% CI, 2.14-3.34]) and ED (OR, 2.02 [95% CI, 1.52-2.67]). For HDPs, the OR increased from 2.48 (95% CI, 1.85-3.33) in the nonexposure group to 3.98 (95% CI, 2.25-7.04) under severe heat exposure. For ED, the lowest risk was observed in the nonexposure group (OR, 1.59 [95% CI, 1.07-2.36]) and the highest in moderate exposure (OR, 3.1 7 [95% CI, 1.42-7.06]). Nonlinear relationships between prepregnancy body mass index and both HDPs and ED were evident, particularly under heat exposure.

Prepregnancy overweight or obesity increased risks of HDPs and ED, with stronger associations under extreme heat. Optimizing prepregnancy weight and mitigating heat exposure may improve maternal cardiovascular health.