For Darshnika Lakhoo, the danger of extreme heat was not something she discovered after becoming a mother. She had spent years studying how rising temperatures affect pregnant women and the health of unborn babies. Yet when Johannesburg experienced repeated heatwaves during her own pregnancy in November 2024, the medical researcher found herself facing complications that she had been warning others about. She eventually delivered her twins six weeks early.

It is difficult to establish how much the heat contributed to her pregnancy complications. Lakhoo was carrying twins, which already increases the risk of premature delivery. But her experience brought an uncomfortable reality closer to home. Even people who understand the dangers of extreme heat cannot always protect themselves from it.

The concern is growing as heatwaves become larger and last longer. Scientists are now examining a pattern of extreme weather events that cover vast geographical areas, sometimes affecting several continents over extended periods. These events are being described as heat storms. Their impact on human health goes well beyond the immediate danger of heat exhaustion and dehydration. For pregnant women, the consequences may include premature labour, high blood pressure, placental complications and health problems affecting newborn babies.

What makes the issue particularly serious is that the danger is not confined to countries with extremely hot climates. Women living in temperate and relatively cool regions are also exposed when temperatures rise beyond what their bodies and local infrastructure are accustomed to handling.

The Temperature Does Not Have to Be Extreme

There is a tendency to associate heat-related pregnancy complications with temperatures above 40 degrees Celsius. That understanding is too narrow. Research increasingly suggests that the rise in temperature relative to the local climate can matter as much as the absolute temperature.

A woman living in a region where temperatures normally remain moderate may experience considerable physical stress when the weather suddenly becomes much hotter. Her home may not have adequate ventilation, public transport may become uncomfortable, and access to cooling facilities may be limited. The body has to adjust to these conditions while already dealing with the physiological demands of pregnancy.

Lakhoo and her colleagues examined nearly 200 scientific studies covering 66 countries. Their review, published in Nature Medicine, found that every one-degree Celsius increase in average temperature was associated with a four percent increase in the odds of premature birth. During heatwaves, the increase reached 26 percent in the week following exposure.

The findings also identified associations between high temperatures and stillbirths, congenital abnormalities and gestational diabetes. Other research has linked heat exposure with pregnancy-related hypertension and preeclampsia, a potentially dangerous condition that can affect the kidneys, heart and other organs.

These findings do not mean that every pregnant woman exposed to high temperatures will develop complications. Nor do they establish that heat is responsible for every premature delivery. Pregnancy outcomes depend on several factors, including maternal age, existing medical conditions, nutrition and access to healthcare. But the consistency of the research across different countries makes it difficult to dismiss heat as a minor concern.

The Danger Is Spreading Beyond Traditionally Hot Regions

One of the more important findings from the research is the geographical reach of the problem. More than a billion women living in temperate and cooler climates may also face increasing exposure as heat events expand.

The changing pattern is particularly worrying because communities in these regions are often less prepared for prolonged heat. Buildings may retain warmth, hospitals may lack sufficient cooling facilities and public transport systems may become difficult to use during extreme weather. People who have lived through occasional hot summers may suddenly find themselves dealing with conditions that continue for weeks.

Johannesburg provides an example. The city is situated at a relatively high altitude and has generally experienced more moderate temperatures than many other parts of southern Africa. Yet during Lakhoo’s pregnancy, the city experienced 74 heat storm days. Temperature records near her home showed around 30 days above 30 degrees Celsius, with more than half occurring during the final month of her pregnancy.

The experience was not limited to one researcher. Pregnant women attending a hospital study in Johannesburg reported headaches, difficulty sleeping and physical exhaustion during unusually hot conditions. Some were living in small rented rooms without air conditioning. Others struggled to find relief even at night.

For many women, the problem is not simply knowing that heat is dangerous. It is having somewhere to escape from it.

South Africa has particularly limited access to household cooling. Only around 7.5 percent of households own an air conditioner. Millions of people also depend on crowded minibuses for daily travel, where temperatures can rise considerably. A pregnant woman may spend hours travelling to work or a medical appointment without access to adequate cooling.

Heat Exposure Can Make Existing Pregnancy Risks Worse

Doctors are increasingly concerned that heat may act as an additional burden on women who already have medical or social vulnerabilities. Pregnancy places greater demands on blood circulation and the cardiovascular system. When temperatures rise, the body must also work harder to regulate its internal temperature.

Dehydration and increased cardiovascular stress can complicate this process. Researchers have suggested that heat may affect blood flow to the placenta, although the precise biological mechanisms remain under investigation. Other possible explanations include changes in hormone activity and additional strain on the developing baby’s cardiovascular system.

The timing of exposure may also matter. Some studies suggest that extreme temperatures during early pregnancy can increase the risk of developmental complications, while heat exposure closer to delivery has been associated with premature birth and stillbirth. There is no single period when all pregnant women face the same level of risk.

The problem becomes more complicated when a woman has hypertension, diabetes or another chronic condition. Older pregnant women and those carrying twins may also face additional risks. These factors can combine, making it difficult to identify how much of a particular complication is attributable to heat.

Research conducted in Mexico provides another indication of the scale of the problem. An analysis of more than eight million births between 2008 and 2025 found that premature deliveries increased when heatwaves occurred during the final month of pregnancy. The increase reached approximately 18 percent among women exposed to the highest levels of heat.

The findings are significant because Mexico has a wide range of climates, from hot deserts to cooler mountain regions. The pattern suggests that the problem is not restricted to one type of environment.

Healthcare Advice Cannot Replace Better Living Conditions

The medical response to heat exposure is still developing. Many maternity facilities do not routinely assess a pregnant woman’s exposure to prolonged heat, even though doctors already monitor blood pressure, diabetes and other risk factors.

That needs to change. Healthcare workers should be able to identify women who spend long hours outdoors, live in poorly ventilated homes or have limited access to drinking water and cooling facilities. Hospitals also need to prepare for increased demand if extreme temperatures contribute to more premature deliveries.

But medical advice alone will not be enough.

Telling a woman to remain indoors during the hottest part of the day is of little help if she earns her living through agricultural work, street vending or domestic employment. Similarly, recommending air conditioning is not a realistic solution for families who cannot afford the equipment or the electricity required to operate it.

This is why the problem needs attention from governments beyond their health departments. Housing standards, workplace regulations, urban planning and public transport all influence how much heat people experience. Providing shaded spaces, reliable drinking water and better ventilation could make a practical difference, particularly in low-income communities.

There is also a need for more research into which protective measures actually work. Air conditioning may offer substantial relief, but it is expensive and not available everywhere. Other interventions, including changes to working hours and improved building design, need to be tested across different climates.

The danger is that maternal healthcare will continue treating heat exposure as an occasional emergency while the weather itself becomes increasingly difficult to predict. For women such as Lakhoo, the experience has already changed the way they approach pregnancy and everyday life. She has become less reluctant to use air conditioning, despite the additional electricity costs.

That may sound like a small adjustment. But it reflects a larger change in how people will have to live as temperatures continue to rise. Pregnancy is becoming another area where the effects of climate change are being felt directly, and healthcare systems have not yet caught up with the speed of that change.

(Adapted from DownToEarth.org.in)

Categories: Sustainability, Uncategorized