Humidity combined with excessive temperatures at the end of pregnancy affects the development of unborn children: 3 million more children at risk by 2050.
Children are among the most vulnerable to the effects of the climate crisis even before they are born: exposure to humidity mixed with excessive heat in the last trimester of pregnancy favors a slowdown in the child’s growth during early childhood in a way that has not been sufficiently considered in climate risk models.
According to a study published in Science Advancesthe hot-humid conditions of the climate we are in building they are much more harmful to infant development than high temperatures alone. This unhealthy mix risks stunting the growth of 3 million more children in South Asia by 2050.
Because humidity makes heat riskier
High humidity inhibits the human body’s natural ability to cool itself through sweating, and pregnant women are at greater risk of health problems if forced to live in hot, humid environments without refrigeration.
As highlighted in the study, excessive heat can cause fluctuations in hormone levels and increase metabolic heat production in expecting women, raising their core temperature. Additionally, dehydration can induce early labor, encourage premature births and low birth weight babies.
Based on analyzes coordinated by scientists at the Climate Hazards Center at the University of California, Santa Barbara, an increase in exposure to hot, humid climates equal to a single standard deviationi.e. a single additional average deviation from the average, slows children’s growth four times more than the same difference in temperature increases alone (without humidity).
A childhood penalized from the start
Researchers observed the effects of exposure to humidity and excessive heat during pregnancy on approximately 200,000 children under the age of 5 in Bangladesh, India and Nepal. In South Asia, vulnerability to climate change is intertwined with poverty and inequalities in access to resources, including food: in 2023, a third of children will be stunted (stunting), or 54 million children, were in this region of the world.
The scientists analyzed temperature and humidity data at various locations where the babies’ mothers lived during pregnancy at a resolution of 10 km, and calculated age-related growth scores to understand who was growing well for their age and who was suffering from slow growth. Exposure to humidity added to heat during pregnancy was found to be much more harmful to growth than heat alone, and could worsen as climate change advances, affecting 3 million to 3.7 million more children than today by mid-century, under a scenario of high levels of climate-altering emissions.
Humidity: an aggravating factor to take into consideration
Low birth weight is associated with adverse effects on children’s growth, and slowed growth under age 5 is a negative indicator for pediatric and future health. In adulthood, this initial deficit can translate into school, health and work difficulties. The study highlights the need to include the effects of humidity in models that calculate the risk posed by excessive temperatures to pregnant women. Maternal health must be considered a priority in tackling the climate crisis.
