Extreme heat and human fertility: Amplified challenges in the era of climate change.

Rising global temperatures and extreme heat events, exacerbated by climate change, pose critical public health challenges, with understudied consequences for human fertility and reproductive health (FRH). While heat-related morbidity and mortality have gained substantial attention, the direct and indirect impacts of thermal stress on FRH-particularly in low- and middle-income countries (LMICs)-remain poorly understood. In LMICs, socioeconomic disparities, environmental vulnerabilities, and cultural norms favoring larger families amplify risks and disproportionately burden marginalized populations. Extreme heat also reduces agricultural productivity, threatening food security and nutritional intake, which can further compromise reproductive health and fertility outcomes. This forum highlights two priorities: (1) the urgent need for interdisciplinary research linking climate science, reproductive biology, and social determinants of health to elucidate heat-FRH pathways, and (2) the development of equitable policies and interventions to mitigate these risks. Emerging evidence suggests that thermal stress can disrupt reproductive processes in both men and women, leading to reduced sperm quality in men, hormonal imbalances, and increased miscarriage risk for women. The compounded effects of extreme heat and air pollution could worsen reproductive health outcomes, especially in low-income, disadvantaged urban neighborhoods, where populations are already vulnerable to climate stressors. Without dedicated research and targeted interventions, climate change could lead to significant demographic shifts, labor shortages, and heightened maternal health burdens in vulnerable populations. This research underscores the need for interdisciplinary work that integrates climate science, reproductive health, and policy development, along with targeted public health strategies to protect FRH in the face of climate change.