December 23, 2025
Rising temperatures combined with increasing humidity due to climate change could significantly worsen child health outcomes in South Asia, potentially leading to more than three million additional cases of stunting by 2050, according to a new study.
The research, conducted by scientists at the University of California, Santa Barbara, examined how exposure to extreme heat and humid conditions during pregnancy affects early childhood development in one of the world’s most densely populated regions. The findings were published in the journal Science.
The study focused on “height-for-age,” a widely used measure of chronic health and nutritional status among children under five. Researchers found that exposure to hot and humid weather during pregnancy—particularly during the earliest and latest stages—was strongly linked to poorer growth outcomes in children.
Pregnant women are especially vulnerable to heat stress because of physiological and hormonal changes that reduce the body’s ability to regulate temperature. High humidity further intensifies this risk by limiting the body’s capacity to cool down through sweating.
The researchers noted that the impacts were most severe when heat and humidity occurred together. Exposure during the third trimester showed health effects nearly four times greater than exposure to high temperatures alone. The study used the wet-bulb globe temperature (WBGT), which accounts for humidity, radiant heat, and airflow in addition to air temperature, to better capture real-world heat stress.
The analysis also revealed demographic effects. Each additional day with a WBGT above 29°C was associated with fewer live births six to twelve months later. In contrast, days with maximum temperatures exceeding 35°C were linked to a temporary rise in births within three months, suggesting shifts in pregnancy timing and possible increases in early-stage pregnancy loss.
According to the researchers, these trends align with earlier studies showing that extreme heat can lead to premature births and reduced conception rates. Hot and humid conditions, they warned, pose a greater risk to fetal development than heat alone.
With climate models projecting a sharp rise in hot and humid days across South Asia under continued global warming, the study cautioned that the true health impacts of extreme weather may be underestimated if humidity is not fully considered.
The research drew on child health data from the Demographic and Health Surveys (DHS) and daily climate data produced by the Climate Hazards Center at UC Santa Barbara.
Source: PTI