Exposure to high levels of heat may both impact the growth of fetuses during pregnancy and infants up to the age of two, a new analysis suggests. The study is the first of its kind to show that heat stress may impact the development of babies after they're born and adds to previous research by the team showing the impact of heat stress on fetal development. The research, which examined data from infants and their mothers collected during a clinical trial in The Gambia, found a small decrease in birth weight for gestational age for every 1°C increase in average daily heat stress during the first trimester.

No effect on growth was observed for heat stress experienced during the second trimester. The research suggested there could be an increase in head circumference compared to the body for gestational age in fetuses exposed to heat stress during the third trimester, but this was less confident. The findings also show that infants up to the age of two exposed to high heat in their environment may have lower weights and heights for their age.

The largest decreases were seen in infants aged between 6-18 months who had experienced higher average daily levels of heat stress in the previous three-month period. At 12 months old, infants exposed to an average heat stress value equivalent to 30°C were more likely to have a reduced weight for their height and age, compared to those who experienced heat stress equivalent to 25°C. The results were found in both male and female infants.

.