Heat Exposure Associated With Rise in Maternal Morbidity

Strong evidence from studies conducted by the University of California, Irvine, links maternal heat exposure during pregnancy to an increased risk of severe maternal morbidity, which could have an impact on public health initiatives and interventions.

In a paper, “Analysis of Heat Exposure During Pregnancy and Severe Maternal Morbidity,” published in JAMA Network Open, the researchers looked into a possible link between severe maternal morbidity (SMM) and maternal exposure to heat.

The study used information gathered from Kaiser Permanente Southern California, a sizable integrated healthcare organization, on 403,602 pregnancies with a mean age of 30.3 years. 3,446 cases of SMM (0.9%) were found among the cohort throughout a ten-year period from 2008 to 2018. Based on their geocoded home addresses, individuals were given temperature values for pregnancy.

The proportions of heat days during pregnancy—divided into moderate, high, and intense heat days—were used to gauge long-term heat exposure. In particular, environmental heat exposure in the third trimester was linked to substantial connections between long-term heat exposure during pregnancy and SMM, according to the study.

Nine distinct heat wave classifications based on temperature thresholds and durations were used to evaluate short-term heat wave exposure during the final week of pregnancy. According to several heat wave classifications, short-term associations were significant. From the least to the most severe heat wave exposure, the size of connections generally increased, with more significant relationships being seen with more severe heat exposure.

According to the Centers for Disease Control and Prevention, SMM “…includes unexpected outcomes of labor and delivery that result in significant short- or long-term consequences to a woman’s health. Using the most recent list of indicators, SMM has been steadily increasing in recent years.”

The authors of the UC Irvine study note that although various theories have been put forth, they are unable to fully account for the increased trend. In 2014, the rate of SMM was over three times higher than it was 20 years earlier.

The beginning of pregnancies (the season of conception) and severe maternal morbidity (SMM) were found to be related. The authors note that compared to women who began their pregnancies in the warm season (May to October), those who did so during the cold season (November through April) were more susceptible to heat exposure and had higher connections with SMM.

This shows that the association between heat exposure and SMM may be influenced by the timing of conception, which results in the stage of pregnancy occurring during the hottest months.

According to the study’s findings, both short- and long-term maternal heat exposure during pregnancy are linked to an increased risk of severe maternal morbidity. These findings have significant ramifications for SMM prevention, especially in light of the present and projected effects of climate change.

The hottest August on record was observed in 2023, according to the World Meteorological Organization and the European Copernicus Climate Change Service. July 2023 was the second-hottest month ever recorded. It is crucial to consider the implications for pregnancy outcomes connected to the heat, particularly in places most impacted by persistent increases.

The report also emphasizes the inequalities in moms’ health based on their degree of education. This indicates the need for focused interventions to lower the risk of SMM, especially for mothers with low socioeconomic level.

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