Maternal heat exposure and offspring congenital heart defects: a systematic review and meta-analysis

Congenital heart defects (CHDs) represent a significant global health concern among birth anomalies. While previous research has explored the potential link between prenatal heat exposure and CHDs in newborns, the findings are still inconclusive. We carried out an extensive literature search across PubMed, Cochrane, Web of Science, and Embase up to February 7, 2025. The assessment of heat exposure encompassed multiple metrics, including extreme heat events (defined as periods above the 90th [EHE90] or 95th [EHE95] percentile of daily maximum temperatures) and continuous measures such as each additional EHE90 event. We used random-effects models in Stata SE15 to analyze the association between heat exposure and health outcomes. Summary risk estimates were based on two criteria: (i) the risk per additional EHEs, and (ii) the comparative risk between high and low exposure levels. Seven studies encompassing 5,138,948 participants (including 330166 CHD cases) met our inclusion criteria. Analysis of extreme heat events as binary exposures revealed a positive trend. While EHE90 exposure was not significantly associated with CHD risk, a borderline significant association was observed for EHE95 (RR = 1.14, 95% CI: 1.00-1.30), indicating an increased risk with more extreme exposure. In continuous exposure analyses, each additional EHE90 and EHE95 event increased the risk by 3% (RR = 1.03, 95% CI:1.02–1.04) and 4% (RR = 1.04, 95% CI:1.03–1.05), respectively. In contrast, the duration of extreme heat events was not significantly associated with CHD risk. This meta-analysis indicates that prenatal exposure to high temperatures, particularly the frequency of extreme heat events, increases the risk of CHD in offspring. These findings highlight the importance of developing public health strategies to mitigate heat exposure during pregnancy. Not applicable.