Extreme temperatures up risk of stillbirth

Pregnant women exposed to extreme heat or cold see a significantly excess risk of stillbirth, especially during the third trimester, reports a recent study.

The study included 22,769 stillbirths in Taiwan, documented between 2009 and 2018. The mean stillbirth rate during this time period was 11.3 per 1,000 births, which peaked during June (12.6 per 1,000 births).

Researchers reported seasonal patterns in stillbirth rates, which showed a primary peak during hot seasons and a second, minor peak during cold seasons. Pearson correlation analysis found that there was a significant link between temperature and stillbirth rate (coefficient, 0.30; p=0.01), but researchers noted that the interaction was nonlinear.

Non-optimal temperature, either too hot or too cold, was responsible for 10.24 percent of all stillbirths. Hot temperature had a higher contribution at 8.34 percent, while cold temperature accounted for only 1.89 percent. Extreme heat (>29^oC) induced 2.64 percent of stillbirths.

At a lag of 0–3 months, researchers found that exposure to extreme heat (29.8^oC) relative to the optimal temperature (21^oC) yielded a cumulative relative risk (CRR) of stillbirth of 2.49 (95 percent CI, 1.24–5.03). Meanwhile, extreme low temperatures (16.5^oC) corresponded to a CRR of 1.29 (95 percent CI, 0.93–1.80). Women in the third trimester of their pregnancies were most susceptible to the effects of extreme temperatures.

“Pregnant women should be informed of the hazardous thermal effect on their unborn infants and protect themselves from extreme temperatures during the critical period,” the researchers said.