Maternal Heat Shock Protein as a Potential Biomarker of Adaptation to Heat Stress during Pregnancy and Its Relation to Preterm Birth.

We evaluated whether maternal HSP27 and HSP70 responded to heat stress during pregnancy and whether HSPs were associated with preterm birth in a secondary analysis of a prospective cohort with repeated biomarkers (N = 227 from MADRES). Serum HSPs were measured during early and late pregnancy using ELISA. Daily heat stress in the 30 days before HSP measurement was computed as Daily Maximum Heat Index (DMHI) and Wet Bulb Globe Temperature (WBGT). Distributed lag models identified sensitive windows of heat adaptation; logistic regression models assessed HSPs' effects on preterm birth (<37 gestational weeks, n = 18 [7.9%]). Models were adjusted for sociodemographics, study design, and heat-exposure predictors. HSP27 and HSP70 concentrations decreased over pregnancy. Higher acute DMHI exposure was associated with higher HSP27 and HSP70 during early pregnancy (1-15 days lags; strongest effect per 1-SD increase: 0.6% [95% CI: 0.001-1.2%] for HSP27 at 9 days; 8.3% [2.6-14.5%] for HSP70 at 1 day) and higher HSP27 during late pregnancy. Mothers with larger HSP70 increases over pregnancy were associated with higher preterm birth risks (OR = 5.2, [1.5, 18.6]) versus those with stable/decreasing levels. HSPs may indicate acute heat stress during pregnancy, with increased HSP70 associated with preterm birth risks.