High levels of heat found to affect foetuses, infants up to age 2: Study

Exposure to high levels of heat could affect growth of foetuses in the womb and infants up to two years of age, an analysis of over 600 pregnancies in the west African country of The Gambia has suggested.

For every degree Celsius rise in average daily heat in the first trimester of pregnancy, the weight of a baby at birth corresponding to gestation period was found to be lowered, according to the findings published in The Lancet Planetary Health journal. One experiences heat stress when their body's ability to regulate temperature is compromised.

The researchers, led by those at the London School of Hygiene and Tropical Medicine (LSHTM), UK, followed a total of 668 infants, about half of whom were girls and half boys, for their first 1,000 days of life.

At birth, 66 infants (10 per cent) were found to weigh under 2.5 kilograms, described as a low birth weight by the researchers. About a third of the infants studied (218) were found to be small for gestational age, while nine infants were born prematurely.

The researchers also found that heat stress experienced by foetuses can continue to affect them after birth -- infants up to two years of age exposed to high heat had lower weights and heights for their age.

The infants aged between 6-18 months who had experienced higher levels of daily heat stress in the previous three-month period were found to be the most affected.

The study is the first of its kind to show that heat stress can hamper development of babies after birth, the researchers said.

As climate change intensifies, the effects of exposure to heat must be urgently considered in public health interventions, they added.

"Our study demonstrates that the intersecting crises of climate change, food insecurity, and undernutrition are disproportionately affecting the most vulnerable, including young children," said lead author Ana Bonell, an assistant professor at the Medical Research Council Unit The Gambia, LSHTM.

The data for analysis was collected as part of a trial, conducted in West Kiang, The Gambia, between January 2010 and February 2015.

"These findings build on previous evidence showing that the first trimester is a vulnerable time to heat exposure and it's important that we now consider which factors may be contributing to the relationship," Bonnell said.

Further research is needed to look at heat stress and its health impacts in regions beyond The Gambia, the researchers said.