During a heat wave, the risk of premature birth increases by 26 %. For each 1°C increase in heat exposure, the risk of premature birth increases by 4%, according to the largest systematic review of its kind published in the journal Nature Medicine. The 198 studies from 66 countries all point in the same direction: heat waves have a direct impact on pregnant women. To try to better prepare for, or even prevent, these premature births, a recent study has identified 23 metabolic pathways and four metabolites associated with both heat exposure and premature delivery.
Daily ambient temperature was recorded for all 215 participants. Heat exposure was calculated for each participant based on their place of residence. Three exposure periods were considered: from conception to the beginning of pregnancy; from the beginning to the end of pregnancy; and from conception to the end of pregnancy. Blood samples were taken from participants at the beginning and end of their pregnancies. Rather than searching for a "threshold" temperature at which a pregnant woman would be at risk, this approach seeks to understand the cumulative effects of heat when temperatures are prolonged. This allows for observation of the entire pregnancy, not just isolated heat waves. This approach reflects the fact that pregnancy can be sensitive to prolonged or cumulative exposure to heat, and not just isolated heat waves.
Measurable changes in the mother's blood
The results, published in the journal Science AdvancesThey no longer set a temperature limit beyond which pregnant women would be in danger. But they illustrate how, degree by degree, changes occur in maternal metabolism. Higher temperatures, especially when maintained for several days or weeks, are associated with measurable changes in certain molecules in the mother's blood." explains Donghai Liang, a molecular epidemiologist at Emory University (USA) and author of this work. These molecules are involved in the stress response and energy metabolism, and are also linked to an increased risk of premature birth."The body can begin to react to heat at levels lower than what is usually considered 'extreme'."
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At the mother's home, each 1°C increase in average temperature between conception and the start of pregnancy was associated with higher levels of certain metabolic pathways (such as methionine). In addition, each 1°C increase in average temperature between conception and the end of pregnancy was associated with lower levels of other compounds (citrulline, etc.).pipecolic acid and proline). Finally, all four metabolites were lower in participants who gave birth before 37 weeks of gestation, compared to those who gave birth at term. This is not surprising, as pregnancy involves major changes in immune function, metabolism, and oxidative stress, and the body can react differently to environmental factors depending on the stage of pregnancy. But pRather than a single critical moment during pregnancy when heat is particularly harmful, biological data indicate a more continuous and prolonged sensitivity to high temperatures.", the researcher continued.
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Coping with the heat
At this stage, the work does not recommend supplementing patients and further clinical studies are needed to define a therapeutic approach. But they pave the way for possible future interventions. Since these metabolic signatures can be detected through a simple blood test, one could imagine tailored care, such as providing pregnant women with nutritional supplements. “Indeed, theMicronutrients involved in antioxidant balance or metabolic resilience could help the body better cope with heat stress during pregnancy. explains Donghai Liang. A way to better cope with the intense heat, which climate specialists predict will increase in the coming years.
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