ASU research shines light on the effect of extreme heat on reproductive health
PHOENIX: Heat-related stress is increasingly recognized not only for its immediate dangers—such as heat exhaustion, cramps and heat stroke—but also for its more insidious effects on human fertility and reproductive health.
In 2024, Maricopa County recorded 608 heat-related fatalities, a modest decline from the 645 deaths reported in 2023, suggesting that public education and prevention measures may be gaining traction. However, growing evidence indicates that extreme heat poses risks far beyond acute medical emergencies, potentially undermining the ability to conceive and sustain healthy pregnancies.
Alamin Molla, a graduate research assistant and PhD candidate at Arizona State University’s School of Geographical Sciences and Urban Planning, argues that the reproductive repercussions of rising temperatures demand urgent attention.
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In his recent forum paper, 'Extreme heat and human fertility: Amplified challenges in the era of climate change', published in the Journal of Thermal Biology, Molla presents a synthesis of studies linking high ambient temperatures with decreased sperm quality and concentration, delayed conception, elevated miscarriage rates and other adverse outcomes.
Much of the existing literature on heat-related health impacts has focused on morbidity — heatstroke, cardiovascular distress and respiratory complications —primarily in high-income settings where air conditioning is widespread.
Molla emphasizes that this bias leaves a critical blind spot regarding low- and middle-income countries, where infrastructural limitations and socioeconomic vulnerabilities amplify heat exposure and reduce adaptive capacity. In these regions, households and workplaces often lack reliable cooling, while nutrition and healthcare access may already be compromised.
Urbanization further compounds the problem through the urban heat island effect, whereby built environments absorb and retain more heat than surrounding rural areas, driving local temperatures even higher. At the same time, climate-driven disruptions to agriculture can lead to food insecurity and nutritional deficiencies—factors that independently undermine reproductive health. Air pollution, which often co-exists with extreme heat, may also interact synergistically to impair fertility.
Women in low-resource settings face unique pressures
In many societies, childbearing is closely tied to cultural identity and social status, and unintended infertility can trigger profound stigma. When extreme heat diminishes reproductive potential, women may experience heightened emotional distress, social isolation, anxiety and depression. Molla warns of a “compounding cycle” in which environmental stress, reproductive challenges and mental health burdens reinforce one another, deepening vulnerabilities.
To address these threats, Molla identifies four priority areas for research and policy intervention.
First, comprehensive scientific studies must establish the biological thresholds at which heat begins to impair male and female reproductive systems.
Second, urban planning and building design should integrate green infrastructure, lower-emission transportation and energy-efficient cooling to reduce population-level heat exposure.
Third, public health programs should expand access to cooling technologies, reproductive healthcare and targeted educational campaigns that inform individuals about the hazards of heat on fertility and pregnancy.
Fourth, mental health services must be scaled up to provide counseling and peer support, helping mitigate the psychological toll of infertility in heat-affected communities.