Rising global temperatures and more frequent extreme weather events are creating significant health risks for vulnerable populations, particularly pregnant women and newborns. A new systematic review of 198 studies from 66 countries highlights the impact of heat exposure on Maternal and Newborn Health, emphasizing the need for targeted public health measures to protect these at-risk groups.
Maternal Health Risks from Heat Exposure
Heat exposure during pregnancy has been linked to a wide range of adverse health outcomes for mothers. Approximately 75% of the studies included in the review identified critical risks associated with heat, such as preterm birth, low birth weight, hypertensive disorders, congenital disabilities, and stillbirth. Notably, heat stress is consistently associated with an increased risk of hypertensive disorders like pre-eclampsia and gestational hypertension, as well as gestational diabetes.
In addition to these conditions, heat exposure during pregnancy has been found to elevate the risk of antenatal bleeding, placental abruption, bacterial infections, and pre-labor rupture of membranes. Mental health was another area of concern, with two studies noting a U-shaped relationship between temperature and emotional stress. Moreover, heat exposure has been linked to higher rates of cesarean sections and cardiovascular events during labor, particularly in the weeks leading up to childbirth.
Fetal and Newborn Health Consequences
Fetal health is also significantly impacted by heat exposure, with stillbirth and congenital disabilities being the most frequently reported outcomes. A meta-analysis revealed that for every 1°C increase in temperature, the risk of stillbirth rose by 1.14 times. Additionally, exposure to heat during the early stages of pregnancy was associated with an increased risk of congenital disabilities, although some studies suggested a protective effect in certain cases.
Fetal growth restrictions and non-reassuring fetal status, which includes fetal hypoxia, were also linked to heat exposure. In some cases, extreme heat increased the risk of spontaneous abortion and perinatal death by 50%. As for newborn health, preterm birth and low birth weight were the most commonly observed heat-related outcomes. The research found a clear dose-response relationship between heat exposure and preterm birth, with a 1.04-fold increase in risk for every 1°C rise in temperature. Heatwaves specifically heightened the risk, with an increase of 1.26 times.
In a major study conducted in the United States, the risk of very low birth weight was found to rise slightly with each additional day of high temperatures. The risk was notably higher among Black and Hispanic mothers, highlighting significant racial disparities in heat-related birth outcomes.
Implications for Public Health and Climate Policy
The findings from this review underscore the urgent need to prioritize maternal and newborn health within national climate and public health programs. Heat exposure during pregnancy can lead to serious complications such as maternal dehydration, hormonal imbalances, and increased inflammation, all of which contribute to poor outcomes for both mothers and their babies. The review’s researchers stress the importance of addressing these risks by incorporating maternal and newborn health considerations into climate resilience strategies.
The research further suggests that understanding the pathophysiological mechanisms behind heat-induced health issues can help in mitigating these risks. These include increased maternal body temperature, electrolyte imbalance, and changes in glucose metabolism. The upregulation of heat shock proteins due to heat exposure may also play a role in premature labor onset and placental insufficiency.
Given the significant evidence linking heat exposure to maternal and newborn health complications, global efforts to combat climate change and promote climate-health adaptation strategies are more critical than ever.
