What impact does climate change have on perinatal mortality? – The link between high temperatures and the risk of stillbirth

Extreme heat can affect both pregnant women and their foetuses. The effects can be indirect to the mother’s environment or directly to the child. Indirect influences include reduced responsiveness and quality of healthcare systems. Direct effects on the child are placental and epigenetic changes. However, especially from areas most affected by climate change and subsequent heat waves, such as sub-Saharan Africa, only very limited data is available. A new study examined over 138,000 births in four African countries. The results show that both high and low temperatures may increase the risk for perinatal mortality as well asthe risk for stillbirth. This highlights the need for improved intrapartum care, especially in low- and middle- income countries (LMICs).

Every year, about 1.9 million infants are stillborn, and an additional 2.3 million neonates die during their first 28 days of life globally. Although some progress has been made in recent years in reducing this high mortality rate, climate change is causing a substantial additional challenge to this effort. High air temperatures may increase the risk of stillbirths. Heat has a negative effect on healthcare systems’ responsiveness and the individuals’ lifestyle, including psychological factors, stress, or environmental factors affecting a mother’s nutrition. In addition, heat may cause embryogenetic and foetal changes as well as placental changes, which can pose a threat to fetal survival and lead to birth defects.

However, there is very little data available on the correlation between heat and birth outcomes, especially from LMICs. In order to investigate the real association, a new study examined over 138,000 births from 16 hospitals located in Benin, Malawi, Tanzania, and Uganda. They examined the correlation between the temperature during the week before birth and the birth outcome.

The association between high temperature and birth outcomes

The study reveals that higher temperatures increase the risk for perinatal mortality by 34%. Especially during the hottest months, the effect was even more significant. Perinatal mortality refers to the rate of foetuses and infants who die within seven days of birth. Stillbirths were divided into antepartum (the infant dies before labour) and intrapartum (the infant dies during labour). The results show no significant association between stillbirths and heat exposure. However, a slightly higher numbers of intrapartum stillbirths were reported after higher temperature, indicating a small correlation. In addition, the analysis showed a U-shaped curve for the risk of temperature-related stillbirth, suggesting that low temperatures may also cause adverse birth outcomes. The risk for stillbirth due to heat exposure was higher for mothers with pre-excisiting conditions such as high blood pressure, for younger mothers, or mothers who already had children.

The study reveals the need for and importance of quality interpartum care

The study emphasises the necessity to protect pregnant and labouring women from extreme heat, especially in regions most affected by climate change. This must happen preventively through early warnings, health promotion recommendations, and especially quality interpartum care. Appropriate and timely obstetric management has the potential to nearly eliminate intrapartum stillbirths. Additional measures may include redesigning clinics and labor wards to reduce heat impacts, especially in LMICs.

Paper available at: https://www.nature.com/articles/s41591-024-03245-7

Ful list of authors: Claudia Hanson, Jeroen de Bont, 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

DOI: https://doi.org/10.1038/s41591-024-03245-7