Exposure to high temperatures during pregnancy disrupts key amino acids and vitamins that help manage stress and energy, increasing the risk of preterm birth, a new study finds. Researchers at Emory University analyzed blood samples from 215 pregnant women in Atlanta, linking hotter ambient temperatures to measurable changes in metabolites such as methionine, proline, citrulline, and pipecolate—molecules involved in amino acid metabolism and oxidative stress regulation. These disruptions were associated with higher rates of babies born before 37 weeks of gestation, offering molecular insight into how heat exposure may contribute to premature delivery.

The study, published in Science Advances, is the first to identify specific molecular pathways connecting environmental heat stress to preterm births. Every 1°C increase in maximum daily temperature from conception to early pregnancy corresponded with higher methionine levels, while increased heat late in pregnancy lowered levels of citrulline, pipecolate, and proline. These amino acids and metabolites play critical roles in how the body manages oxidative stress and produces energy, which are essential for a healthy pregnancy. The findings suggest that elevated temperatures trigger biological strain, potentially leading to premature labor.

Lead author Donghai Liang explained that using metabolomic technology allowed researchers to detect these molecular "fingerprints" for the first time, revealing how heat impacts stress response pathways in pregnant women. The insights gained could lead to early biomarkers for identifying pregnancies at higher risk of preterm birth and inform prevention or intervention strategies to protect maternal and infant health. Preterm birth remains a leading cause of infant illness and mortality, and understanding its connection to environmental factors is crucial in a warming climate.

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The data underlying the analysis came from the Atlanta African American Maternal-Child Cohort study, begun in 2014, emphasizing both racial and regional health contexts. Previous research showed links between heat, oxidative stress, inflammation, and adverse birth outcomes, but this study provides more specific molecular targets. With climate change increasing the frequency of extreme heat events worldwide, these findings carry urgent implications for public health policies aimed at safeguarding vulnerable pregnant populations from heat-related risks.

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