The climate crisis is damaging the health of foetuses, babies and infants across the world, six new studies have found.
Scientists discovered increased heat was linked to fast weight gain in babies, which increases the risk of obesity in later life. Higher temperatures were also linked to premature birth, which can have lifelong health effects, and to increased hospital admissions of young children.
The studies, published in a special issue of the journal Paediatric and Perinatal Epidemiology, spanned the globe from the US to Denmark, Israel and Australia.
"From the very beginning, from preconception, through early childhood into adolescence, we’re starting to see important impacts of climate hazards on health,” said Prof Gregory Wellenius, who edited the issue with Amelia Wesselink, both at the Boston University school of public health, in the US.
The link between heat and rapid weight gain in the first year of life was found by scientists in Israel. They analysed 200,000 births and found that babies exposed to the highest 20% of night-time temperatures had a 5% higher risk of fast weight gain.
Globally, 18% of children are now overweight or obese. A possible mechanism for the rapid infant weight gain is that less fat is burned to maintain body temperature when the ambient temperature is higher.
Two new studies examined the link between high temperatures and premature birth. The first assessed almost one million pregnant women in New South Wales, Australia, from 2005 to 2014, of whom 3% delivered their babies before 37 weeks.
The researchers found that those in the hottest 5% of places in the state in the week before birth had a 16% higher risk of premature birth. Previous research had found a similar effect in the warmer sub-tropical city of Brisbane, but this was the first in a more temperate region of Australia.
The second study analysed 200,000 births from 2007-2011 in Harris County, Texas – which includes Houston – where people are accustomed to heat. The period included Texas’s hottest summer on record in 2011.
A quarter of the mothers were exposed to at least one very hot day while pregnant, days when temperature reached the top 1% of historic summer temperatures. The risk of any premature birth was 15% higher the day after these very hot days, the scientists found. But the risk was even higher for especially early births, tripling for babies born before 28 weeks, and was also higher for the most disadvantaged 20% of the mothers.
Hotter temperatures also increased the number of admissions of young children to emergency departments in New York City, another new study found. The scientists looked at 2.5m admissions over eight years and found that a 7C rise in maximum temperature led to a 2.4% increase in admissions in under-fives. Young children lose proportionally more fluids than adults and their ability to regulate their body temperature is immature, the researchers said.
The burning of fossil fuels drives the climate crisis but also causes air pollution and a new study in Denmark assessed the impact of dirty air on 10,000 couples trying to conceive naturally. It found that increases in particle pollution of a few units during a menstrual cycle led to a decrease in conception of about 8%.
Wellenius said an important aspect of the studies was that they showed that vulnerable people often suffered the worst effects, for example people of colour and those on low incomes who did not have air conditioning or lived in areas with higher air pollution. “This is absolutely a health equity and justice issue,” he said.