Heat exposure in pregnancy: Pregnant women exposed to higher temperatures may experience changes in certain amino acids and vitamins that help the body manage stress and produce energy, potentially increasing the risk of preterm birth, a new study suggests.
Preterm birth, when a baby is born before 37 weeks of pregnancy, has previously been linked to warmer ambient temperatures. The new research goes a step further by identifying specific biological changes that may help explain this association.
Published in the journal Science Advances, the analysis used metabolomics, the study of small molecules in the blood, to examine “molecular fingerprints” in samples from 215 pregnant women living in the Atlanta metropolitan area in the US.
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Researchers from Emory University matched each woman’s residential address with the maximum daily temperatures recorded across different stages of her pregnancy.
The team found that higher ambient temperatures were associated with disruptions in the levels of several naturally occurring substances in the blood, including methionine, proline, citrulline and pipecolate. These metabolites play roles in amino acid metabolism, energy production and the body’s response to oxidative stress.
Methionine is an essential amino acid obtained from dietary sources, whereas citrulline is produced during the urea cycle. Pipecolate is involved in the body’s response to oxidative stress and is found mainly in the liver.
Using metabolomic technology, the researchers observed that when the weather was hotter, pregnant women’s blood showed measurable changes in molecules and pathways that help the body cope with stress and generate energy. Similar patterns were also seen in women who went on to deliver prematurely.
In total, the authors reported 23 metabolic pathways and four overlapping metabolites, methionine, proline, citrulline and pipecolate. that were linked to both higher temperature exposure and preterm birth. These pathways are largely related to amino acid metabolism and the regulation of oxidative stress.
The study also found that every 1°C increase in the average daily maximum temperature between conception and early pregnancy was associated with higher methionine levels. In contrast, a 1°C increase between conception and late pregnancy was tied to lower levels of citrulline, pipecolate and proline.
The authors say their findings highlight the potential of metabolomics to detect early biological changes linked to environmental risk factors and adverse birth outcomes. Identifying shared metabolic pathways between heat exposure and preterm birth could, in the future, help in developing early biomarkers to flag pregnancies at higher risk and guide prevention or clinical interventions.
