Exposure to extreme heat conditions is resulting in more babies being born with low birth weight, according to a new study involving Adelaide University researchers.
The collaborative study, published in BMC Medicine, used health data from more than 85,000 mothers and babies in Pakistan to assess the impact of extreme heat on the size of infants.
“We found pregnant women in this study were at a higher risk of delivering infants of a low birth weight following exposure to extreme temperatures,” said project lead Associate Professor Zohra Lassi from Adelaide University’s Robinson Research Institute.
“That risk was up to 70 per cent higher in some areas of Pakistan, which are more susceptible to adverse birth outcomes due to their hotter climate and greater socioeconomic disadvantage, among other factors.”
The researchers used a combination of ten years of birth data (2008-2017) and monthly mean temperature exposure to determine the link between heat and birth weight.
Eighteen per cent of babies were found to have low birth weight, defined as weighing less than 2.5 kilograms or being described as smaller than average in size at birth.
Up to 13 per cent of the low birth weight cases were attributed to hot weather conditions, with this burden projected to increase by around 8 to 10 per cent by the 2060s due to climate change.
“Low birth weight is already a major neonatal health issue in Pakistan, leading to neonatal mortality and impaired long-term health problems such as stunted growth or cognitive defects,” said Associate Professor Lassi.
Pakistan has experienced more frequent heatwaves, droughts and floods in recent decades, increasing concerns for the health and welfare of mothers and babies.
“In Pakistan, heat does not occur in isolation. It interacts with existing challenges such as poverty, limited healthcare access, poor air quality, and maternal undernutrition, which means climate change can deepen risks for mothers and newborns in ways that are far from equal,” said lead author Hira Fatima, a Postdoctoral Research Fellow from the HEAL Global Research Centre at the University of Canberra.
“Our study shows that these structural disadvantages are already shaping who is most at risk of heat-related low birth weight.”
As part of this study, researchers created a heat vulnerability index to identify the provinces at greater risk of low birth weight linked to hotter temperatures, with Southern Punjab, northern Sindh and Baluchistan considered the most susceptible.
“Our findings show that climate adaptation in Pakistan cannot stop at heat warnings alone. It needs to include stronger maternal health services, better protection for vulnerable pregnant women, and targeted support for the districts facing the greatest heat risk,” said Dr Fatima.
“Interventions designed to mitigate the effects of climate change, enhance access to essential healthcare services, and promote sustainable development are urgently required,” said Associate Professor Lassi.
“This includes public health programs to educate and help pregnant women to cope with extreme heat events, along with much-needed investment in improvements to health infrastructure.”
While the study focused on data from Pakistan, researchers believe the findings have important implications for many other countries bracing for a future of extreme heat, with global mean temperatures expected to remain at record levels.
“These insights are highly relevant for other countries facing rising temperatures, including Australia, and highlight the need for public health preparedness and climate-adapted maternal care strategies,” said Associate Professor Lassi.