Flood exposure during pregnancy and risk of preterm birth: A study of 25 countries from Africa

As climate change intensifies, floods are increasingly disrupting maternal healthcare access, elevating stress, and heightening infection risks—all established triggers for preterm birth (PTB). Investigating this association is therefore an urgent public health priority, particularly in African countries, which bear a high burden of PTB in the world yet possess the least adaptive capacity to mitigate these escalating climate threats. Therefore, we utilized data from the Demographic and Health Surveys to estimate these associations across 25 African countries. We included 587,310 birth records (567,349 singletons and 19,961 multiples) in this study, among which 20,931 (3.56%, 18,750 singletons and 2181 multiples) were classified as PTB cases. Exposure to flood during the trimester 2 was associated with an increased PTB risk (OR = 1.07, 95%CI: 1.01−1.15), particularly in Southern Africa (OR = 1.20, 95%CI: 1.06−1.35), and Western Africa (OR = 1.26, 95%CI: 1.06−1.49). Stratified analyses by flood severity showed that the OR (95%CI) of PTB was the largest for exposure to extreme flood (OR = 1.27, 95%CI: 1.10−1.46) during the trimester 2. Exposure to flood with a duration≤ 2 weeks (OR = 1.10, 95%CI: 1.01−1.22) had a greater impact than those with a duration > 2 weeks (OR = 1.07, 95%CI: 0.98−1.16, P for difference = 0.607). Joint analyses on the severity and duration of flood indicated that flood with short duration have increased PTB risk during the trimester 2. Our findings suggest that flood exposure during the trimester 2 was associated with elevated PTB risk in Africa, underscoring the urgent need for developing resilient support systems and adaptive measures to protect at-risk groups including expectant mothers.