Relative high heat exposure increases the likelihood of adverse birth outcomes: Multi-country evidence of heat impacts on birth outcomes

Relative high heat exposure increases the likelihood of adverse birth outcomes: Multi-country evidence of heat impacts on birth outcomes | Research Square Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Article Relative high heat exposure increases the likelihood of adverse birth outcomes: Multi-country evidence of heat impacts on birth outcomes Lebohang Radebe, Chloe Brimicombe, Michalis Koureas, Federica Nobile, and 27 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9092562/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Extreme high temperatures pose a growing threat to perinatal health, which is expected to intensify with accelerating climate change. While there is a growing body of evidence documenting heat-perinatal health outcomes, comparing studies worldwide poses multiple challenges, including heterogeneity in study designs and heat metrics. Furthermore, evidence from low-and-middle income countries is particularly underrepresented in the global evidence base. Using over 5 million births from hospital (11 locations), regional (two locations) and national (three countries) registry data across Africa, Europe and Latin America and the Caribbean (LAC), we employed a time-stratified case-crossover design to evaluate the association between short-term (<7 days) heat exposure comparing different heat metrics (temperature, Wet Bulb Globe Temperature, Universal Thermal Climate Index (UTCI), and heat index) and birth outcomes (preterm birth [PTB], stillbirth and low Apgar score). Here we show that compared to the 75th percentile of maximum UTCI, the 99th percentile was associated with 1.10-fold higher odds of PTB [95%CI: 1.07-1.14], with stronger heat-exposure associations in hospital-based registries in Africa (OR=1.22 [95%CI:1.05-1.42]) and LAC (OR=1.27 [95%CI :0.90-1.79]) than population-based registries in Europe (OR=1.10 [95%CI: 1.08-1.11]). We observed a 1.09-fold increase in the odds of stillbirth [95%CI: 0.92-1.27] and 1.08-fold increase in low Apgar score [95%CI: 0.99-1.18], with higher risks in Africa compared to Europe. All heat exposure metrics were highly correlated, with similar effect estimates observed, but slightly higher effects using UTCI in more humid countries. As one of the largest studies using harmonised statistical approaches, we provide robust estimates of the detrimental associations of heat on multiple birth outcomes, with stronger associations in low- and middle-income settings, highlighting the disproportionate vulnerability of these populations. Health sciences/Risk factors Scientific community and society/Developing world Health sciences/Health care/Public health/Epidemiology Health sciences/Health care/Health policy Birth outcomes Climate change Environmental epidemiology Heat exposure assessment Short-term heat exposure Full Text Additional Declarations There is NO Competing Interest. Supplementary Files 20260309SupplementaryMaterials.docx Supplemental Materials to Relative high heat exposure increases the likelihood of adverse birth outcomes: Multi-country evidence of heat impacts on birth outcomes Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information

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