Heat waves can lead to poor pregnancy outcomes, a study review found.
The analysis in BMJ included 70 studies in 24 countries and found that overall, every one degree Celsius (1.8 degrees Fahrenheit) increase in temperature was associated with a 5 percent increase in premature births and 5 percent increases in stillbirths.
Heat waves – generally two days or more of unusually high temperatures – were associated with a 16 percent increased chance of premature birth and a 46 percent increased risk of stillbirth. The effects of high temperature were greatest in the last month of pregnancy. There was no influence of temperature on birth weight.
The evidence was strongest and most consistent for the negative effects of heat waves, but several studies found that large variations in daytime temperatures or high nighttime temperatures were also associated with premature births.
“Overall, high temperatures are harmful to health,” said lead author Matthew Francis Chersich of the University of Witwatersrand in Johannesburg. “It’s not just heat stroke from a marathon runner or someone stuck in the desert. Pregnant women are at higher risk; poor women are much worse – wherever people do not have access to air conditioning. “
Still, he said, pregnant women shouldn’t be afraid to go for a walk on a hot day. “There is a slightly higher risk if she is repeatedly exposed to high temperatures. It is repeated, frequent exposure that puts a baby at unnecessary risk. “