Extreme heat severely impacts human and planetary health. Some populations are more at risk of adverse health outcomes during extreme heat events, and particular windows in the life course, including pregnancy, confer greater risk. Substantial physiological change occurs in pregnancy which includes altered thermoregulatory pathways. As the fetus is dependent on the maternal body for heat dissipation, if heat exchange with the external environment is compromised, it can disrupt maternal, placental, and fetal physiology.
Epidemiological studies, including within Australia, associate heat exposure in pregnancy with complications such as miscarriage, congenital anomalies, low birth weight, stillbirth, and preterm birth. However, the physiological and endocrine change underpinning these complications is surprisingly unclear. There is a lack on conclusive evidence regarding how the pregnant body responds to heat, what heat exposure conditions are of concern, and how this affects pregnant biology such as changes in placental blood flow, pathways in labour onset, inflammation, and infection. While animal studies have in part helped with mechanistic understanding there are considerable limitations that urgently need to be addressed.
Further, while the external environment may be hot, the overlay of socio-economic, occupational, and cultural characteristics has a profound impact on how pregnant people are exposed to heat. There is currently a large gap in our understanding of how the climatic conditions of the external environment compare with what people are actually exposed to. Therefore collectively, the substantial gap in biological understanding is exacerbated by a lack of engagement with people who are living with extreme heat. Yet, unlike other extreme events associated with climate change, the adverse health impacts of extreme heat are largely preventable. Transdisciplinary approaches and understanding are critical for conclusively addressing these gaps and developing strategic interventions to prevent pregnancy complications during extreme heat.