Research indicates that extreme heat exposure during pregnancy is associated with adverse birth outcomes, including preterm delivery, low birth weight, and other health complications.
Key facts
- •A review of 70 studies found a 16% higher chance of preterm birth during multiday heat waves.
- •Exposure to temperatures of 86 F (30 C) or higher for at least 15 days in the first trimester was linked to a 6% higher risk of critical heart defects in newborns.
- •Combined risks of poor pregnancy outcomes rise by 20% when temperatures reach 102 F (39 C).
- •A study of 56 million U.S. births found that deliveries on days with temperatures above 90 F (32.2 C) were typically six days earlier than expected.
- •Four consecutive days of extreme heat in the final week of pregnancy were linked to a 3% increase in the risk of stillbirth.
Rising global temperatures are increasingly linked to health risks for pregnant individuals, who experts say are physiologically more vulnerable to extreme heat. Studies suggest that heat exposure may contribute to adverse outcomes such as preterm birth, low birth weight, and pregnancy-related complications like preeclampsia. Researchers are currently working to identify specific heat thresholds that pose the greatest danger to maternal and prenatal health.
By the numbers
Physiological Impacts of Heat
When the body attempts to cool itself in high temperatures, blood flow is redirected to the skin's surface, which may decrease blood flow to the placenta. This reduction can limit the supply of oxygen and nutrients to the fetus, potentially leading to low birth weight. Additionally, heat stress may elevate cortisol levels, which could affect placental function and fetal development.
Links to Preterm and Early Birth
Research suggests a correlation between extreme heat and preterm delivery, defined as birth before 37 weeks of gestation. A review of 70 studies found that the risk of preterm birth increases by 16% during multiday heat waves and by 5% for every 1.8 degrees Fahrenheit (1 degree Celsius) increase in average temperature throughout pregnancy. High temperatures are also associated with early births, which occur between 37 and 39 weeks.
Mitigation and Socioeconomic Factors
The impacts of heat are often more severe for individuals in disadvantaged socioeconomic conditions who may lack access to air conditioning or live in areas with limited green space. Experts suggest that expanding urban green spaces and implementing early-warning systems, such as mobile applications that forecast heat stress, could help mitigate these risks.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by Live Science.
