Association between first trimester ambient temperature and the risk of gestational hypertension and pre-eclampsia: Insights from the PRECISE study cohort in The Gambia, Kenya and Mozambique

Background : Heat exposure during pregnancy has been linked to adverse maternal health outcomes. However, evidence regarding the relationship between ambient heat and hypertensive disorders of pregnancy (HDP) mixed with limited evidence from low- and middle-income countries (LMICs) in sub-Saharan Africa. Methods: We examined the association between ambient heat exposure and HDP among women in the PRECISE pregnancy cohort (The Gambia, Kenya and Mozambique). Logistic regression models estimated associations between pregnancy window and preconception pregnancy windows and risk of HDP. Results and Discussion: The cohort analysis subset HDP incidence was 15.9%. HDP status varies by maternal age, education, and other characteristics. Each 1°C increase in first-trimester temperature was associated with 8% increased odds of HDP (aOR 1.08, 95%CI:1.04 to 1.13, p<0.001). A similar relationship was observed for preconception heat exposure. Conclusion: First trimester heat exposure was associated with increased HDP risk, highlighting early pregnancy as a critical window for targeted interventions.