Heat increases the risk of miscarriage

With rising temperatures, the number of late premature births also increases. At what point does heat become a risk for the child?


Miscarriage, a devastating loss experienced by many couples, is a subject of ongoing research. While various factors contribute to the occurrence of miscarriage, recent studies have shed light on the potential link between heat exposure and an increased risk of pregnancy loss. This article aims to delve into the scientific evidence behind this connection, providing insights into the mechanisms involved and highlighting the importance of understanding and addressing the impact of heat on maternal health.

heat linked to miscarriages

Heat and Pregnancy: Exploring the Connection:

Research conducted in recent years has indicated a correlation between exposure to high temperatures and an elevated risk of miscarriage. The increased prevalence of heatwaves due to climate change has brought this issue to the forefront. Heatwaves can lead to significant rises in ambient temperatures, and when pregnant women are exposed to such extreme heat, it can have adverse effects on fetal development and maternal well-being.

Mechanisms at Play: Several mechanisms may explain how heat affects the risk of miscarriage. Firstly, excessive heat can lead to physiological changes in the maternal body, such as dehydration and increased core body temperature. These changes can disrupt the delicate balance necessary for successful pregnancy and potentially harm the developing foetus.

Moreover, heat stress can induce oxidative stress, which occurs when the body’s antioxidant defences are overwhelmed by harmful free radicals. Oxidative stress has been linked to various pregnancy complications, including miscarriage. Heat-induced inflammation and hormonal imbalances may also contribute to the increased risk.

Scientific Evidence: Studies investigating the impact of heat exposure on pregnancy outcomes have provided compelling evidence. For instance, research conducted in Sweden found that exposure to high temperatures during early pregnancy was associated with a higher risk of miscarriage. Similarly, a study in the United States observed an increased risk of pregnancy loss among women exposed to heatwaves during the first trimester.

Preventive Measures and Public Health Implications: Understanding the potential risks associated with heat exposure during pregnancy is crucial for healthcare professionals and policymakers alike. It is essential to develop effective strategies to mitigate these risks and protect the health of pregnant women and their unborn children.

Education and awareness campaigns can help inform expectant mothers about the importance of avoiding excessive heat, staying hydrated, and seeking cool environments during periods of high temperatures. Additionally, urban planning and infrastructure development can prioritize measures to reduce urban heat island effects and provide heat-safe public spaces.

From the third day of heat, it becomes risky

When it is hot, pregnant women should stay in cool rooms if possible. Especially if there are several hot days in a row, the risk that the child will be born prematurely increases.

A team from the University Hospital Eppendorf (UKE) in Hamburg examined the effects of heat waves during pregnancy. “It was noticeable that the expectant mothers were obviously able to get through one or two hot days. But if a third, fourth, fifth day followed without cooling down, premature contractions would start to increase. And this is especially the case when high humidity increases the perceived warmth,” explains study leader Prof. Petra Arck from the Centre for Obstetrics, Paediatrics and Adolescent Medicine at the UKE.

The researchers did not observe that heat stress could also increase the number of premature births before the 34th week of pregnancy: “Other reasons often play a role, such as ascending infections, maternal illnesses,” explains Arck when asked by NetDoktor.

At 35 degrees 45 percent higher risk

For the study, her team analysed anonymized data from more than 42,000 pregnant women who had given birth at the UKE in the past 20 years. The researchers compared the calculated and actual birth dates with the climate tables of the Hamburg Weather Service. In doing so, they concentrated on the period from March to September.

The result: temperatures of 30 degrees Celsius increased the risk of preterm birth by 20 percent, temperatures over 35 degrees even by 45 percent.

Poor care for foetuses

Heat waves that last for days or weeks are extremely stressful for pregnant women: “Because the stomach is pressing on the main vein, not so much blood gets to the heart,” says Arck. The blood vessels dilate due to the constant heat, which intensifies this effect.

The researchers also observe such heat-induced vasodilatation in the uterus. “Our data suggest that heat stress can trigger redistribution of blood not only to the skin but also to the foetus. This impairs the supply of oxygen and nutrients to the growing baby,” explains Arck.

Will every sixth child be born prematurely in 2033?

In 2033, almost every sixth child could be born prematurely due to rising temperatures, the researchers calculated. That would be twice as many as today. “The consequences of this for the health of new-borns cannot yet be foreseen,” says the scientist.

Doctors speak of a premature birth when children are born before the 37th week of pregnancy. “A birth before the 37th week of pregnancy is associated with an increased risk of health problems later in life,” explains co-study leader Prof. Anke Diemert, who looks after pregnant women in the obstetrics clinic.

“Everyday counts”

A so-called “late premature birth” between the 34th and 37th week of pregnancy can also have a disruptive effect on the development of the child. The lungs, digestive and immune systems, among other things, still have to mature. “Every day counts here,” says the doctor. According to studies, concentration disorders, poorer school performance, a higher risk of infections, allergies, asthma and obesity are possible consequences of a premature birth.

So, what to do in case of heat stress? Arck recommends women between 34 and 38 weeks pregnant when temperatures are persistently high.

  • avoid the sun as much as possible.
  • stay in air-conditioned rooms.
  • drink lots of fluids

Research Findings

Heat exposure has emerged as a potential risk factor for miscarriage, highlighting the need to address the adverse effects of high temperatures on maternal health. By gaining a deeper understanding of the mechanisms involved and implementing preventive measures, we can take significant steps towards safeguarding the well-being of pregnant women and reducing the incidence of miscarriage associated with heat exposure.

The Middle East region is known for its hot and arid climate, with extreme temperatures experienced throughout the year. Heatwaves are a frequent occurrence, posing significant challenges to the health and well-being of individuals, particularly pregnant women. The combination of high temperatures and pregnancy creates an environment where the risk of miscarriage may be heightened.

Studies specific to the Middle East have yielded noteworthy findings regarding the impact of heat on miscarriage risk. For example, research conducted in countries like Saudi Arabia, UAE, and Qatar has demonstrated a correlation between heat exposure and an elevated likelihood of pregnancy loss. These studies have examined the influence of ambient temperatures and heatwaves during various stages of pregnancy, shedding light on the vulnerability of expectant mothers to heat-related complications.