Climate change's mounting threats to maternal health now include a critical vulnerability window that affects hundreds of thousands of pregnancies annually. Women who previously delivered prematurely face substantially elevated risks when exposed to high temperatures during subsequent pregnancies, while first-time mothers and those without preterm birth history show no such temperature sensitivity.
Analysis of 131,599 births across Southern Israel revealed that maternal history fundamentally alters how ambient temperature affects pregnancy outcomes. Women with previous preterm deliveries showed a 9% increased risk of early delivery when temperatures reached 31°C compared to 16°C, with vulnerability emerging as early as nine weeks into pregnancy and intensifying throughout gestation. The effect strengthened progressively, peaking in the final weeks before delivery. Remarkably, this temperature-birth timing relationship was completely absent in women without preterm birth history, regardless of whether they were first-time mothers or had successful full-term pregnancies.
This finding reshapes clinical understanding of environmental pregnancy risks by identifying a specific high-risk maternal phenotype. The research suggests that previous preterm birth creates lasting physiological changes that amplify heat sensitivity in subsequent pregnancies. While the study also detected potential increased cold sensitivity among women taking antihistamines and heat sensitivity in those with autoimmune conditions, these associations require further validation. For reproductive medicine, this represents a paradigm shift toward personalized environmental risk assessment, where maternal history becomes as important as current pregnancy monitoring in predicting climate-related complications.