Rising temperatures in Africa may increase perinatal deaths

Heatwaves in sub-Saharan Africa are predicted to become more common due to climate change. A new study by researchers at Karolinska Institutet and others, published in Nature Medicine, reveals a worrying correlation between high temperatures in the final week of pregnancy and an increased risk of stillbirth and early neonatal mortality.

“While temperatures are rising in sub-Saharan Africa, knowledge of how they affect pregnant women and their babies is scant,” says the study’s corresponding author Claudia Hanson, docent at the Department of Global Public Health, Karolinska Institutet, Sweden.

“Our results indicate that mother and newborn care in this region must be improved to ensure that hard-won improvements in reducing mortality are not lost to climate change,” adds Andrea Pembe, professor at the Department of Obstetrics and Gynaecology, Muhimbili University of Health and Allied Sciences, Tanzania.

The study included over 138,000 births at 16 hospitals in four countries in sub-Saharan Africa: Benin, Malawi, Tanzania and Uganda. The researchers analysed the association between high temperatures in the week before birth and perinatal mortality, which is to say a death just before, during, or within 24 hours after birth. High temperatures were defined as an increase in average weekly temperature for a typically warm week (between 22 and 28 °C depending on country, corresponding to the 75^th percentile) to an exceptionally warm week (between 24 and 29 °C, corresponding to the 99^th percentile).

Babies whose mothers had been exposed to high temperatures the week before childbirth had a 34 per cent higher risk of perinatal death, a risk that doubled during the six hottest months of the year. Unlike in many other countries, a large proportion – almost half – of all stillbirths occurred during labour.

“Our study shows that there is an urgent need to develop and implement interventions that protect pregnant women and their babies during heatwaves,” says co-lead author Jeroen de Bont, a postdoctoral researcher in Petter Ljungman’s research group at the Institute of Environmental Medicine, Karolinska Institutet.

In sub-analyses of heat-associated mortality by timing of death (before, during or after labour), the researchers observed trends towards increased stillbirths during labour, but not all estimates reached statistical significance.

The next phase of the research needs to focus on redesigning maternity wards to mitigate the effects of heat on pregnant women and staff, including using improved construction techniques such as ceiling insulation, and creating adjacent green areas, which can bring additional health benefits. The researchers will also be studying how heat affects other maternal and childbirth outcomes, and how it interacts with environmental factors such as air pollution.

The study was primarily financed by the EU’s Horizon 2020 research and innovation programme and was carried out in close collaboration with Makerere University, Uganda, Muhimbili University of Health and Allied Sciences, Tanzania, Centre de Recherche en Reproduction Humaine et en Démographie (CERRHUD), Benin, and Kamuzu University of Health Science, Malawi. The researchers report no conflicts of interest.

Facts: Every year, 1.9 million babies around the world die just before or during childbirth (stillbirth) and an additional 2.3 million die during the neonatal period (within the first 28 days of life). Sub-Saharan Africa is the region with the highest mortality rates. Reducing the stillbirth and neonatal mortality rates is one of the UN’s sustainable development goals and the principal objective of the WHO’s Every Newborn Action Plan initiative.

Publication: “A time-stratified, case-crossover study of heat exposure and perinatal mortality from 16 hospitals in sub-Saharan Africa”, Claudia Hanson*, Jeroen de Bont* (joint first-authorship), Kristi Sidney Annerstedt, Maria del Rosario Alsina, Federica Nobile, Nathalie Roos, Peter Waiswa, Andrea Pembe, Jean-Paul Dossou, Effie Chipeta, Lenka Benova, Hussein Kidanto, Cherie Part, Massimo Stafoggia, Veronique Filippi, Petter Ljungman, Nature Medicine, online 3 September 2024, doi: 10.1038/s41591-024-03245-7.