Heat Exposure Increases Risks of Preterm Birth Through Maternal Hypertension: Study
China: Heat exposure in early pregnancy can raise the risk of maternal hypertension, thereby affecting preterm birth (PTB) incidence, a large population study has found. The findings, published in Nature Medicine, have implications for active monitoring and maternal blood pressure (BP) management during prenatal care.
Pregnant women are particularly vulnerable to the effects of heat due to physiological changes that affect thermoregulation and cardiovascular function. When exposed to elevated temperatures, the body's ability to dissipate heat efficiently is compromised, leading to increased core body temperature. This physiological response can trigger a cascade of events, including dehydration, increased blood viscosity, and vasoconstriction, which contribute to elevated blood pressure.
Heat exposure is associated with an increased risk of PTB, with previous studies suggesting that maternal BP may play a role in these associations. Considering this, Liyun Wang, School of Public Health, Sun Yat-sen University, Guangzhou, China, and colleagues conducted a cohort study of 197,080 singleton live births across eight provinces in China from 2015 to 2018.
The study estimated the associations between heat exposure, maternal hypertension, and clinical subtypes of PTB, and mediation analyses quantified the role of maternal hypertension in heat and PTB.
The following were the key findings of the study:
- Heat exposure (>85th, 90th, and 95th percentiles of local temperature distributions) spanning from conception to the 20th gestational week was associated with a 15–21% increase in PTB and a 20–22% increase in medically indicated PTB.
- Heat exposure is likely to increase the risk of maternal hypertension and elevated blood pressure.
- Maternal hypertension mediated 15.7% and 33.9% of the effects of heat exposure (>90th percentile) on PTB and medically indicated PTB, respectively.
In conclusion, addressing the risks associated with heat exposure during pregnancy is pivotal in reducing the incidence of preterm birth mediated by maternal hypertension. Heightened awareness, proactive healthcare practices, and supportive environmental policies are essential in safeguarding fetal and maternal health amidst increasing climate challenges.
Reference:
Wang, L., Di, J., Wang, Q., Zhang, H., Zhao, W., Shi, X., Di, Q., Ji, J. S., Liang, W., & Huang, C. (2024). Heat exposure induced risks of preterm birth mediated by maternal hypertension. Nature Medicine, 1-8. https://doi.org/10.1038/s41591-024-03002-w
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