Does Heat Put Your Pregnancy at Risk?

Could rising temperatures be putting your pregnancy at risk?

What the Research Found

A large 2025 review pooling 198 studies from 66 countries looked at exactly this question, and the pattern held up remarkably well despite differences in how each study measured “heat.” For every 1°C rise in ambient temperature, the odds of preterm birth ticked up by about 4%. During heatwaves, that risk jumped much further — by as much as 26%. The same review also found higher odds of congenital anomalies, gestational diabetes, and other obstetric complications when heat exposure increased.

Heat doesn’t just seem to affect labor and delivery, either. A large case-crossover study of more than 17,000 pregnant patients in Quebec, Canada found that weeks with a maximum temperature of 86°F (30°C) carried a higher risk of placental abruption at term (when the placenta separates from the uterine wall before delivery) compared with cooler weeks around 59°F (15°C).

What This Means If You’re Pregnant

None of this means a hot day will harm your pregnancy — the increase in risk per degree of temperature is modest, and pregnancy outcomes depend on many overlapping factors.

If you’re pregnant and live somewhere prone to extreme heat, it’s worth talking to your obstetric provider about practical ways to limit heat exposure — staying in air-conditioned or shaded spaces during the hottest parts of the day, staying well hydrated, and pacing outdoor activity.