Investigating the Biological pathways from HEAT exposure to preterm birth and other adverse maternal and child health outcomes in South Africa (the Bio-HEAT study)

Approximately 190 studies have documented linkages between heat exposure, and adverse maternal and child health outcomes. Understanding the underlying biological vulnerabilities that explain these linkages is especially important given rising global temperatures and the urgent need for adaptive interventions. Applying transdisciplinary research in Johannesburg, South Africa, we will follow 200 women from the second trimester until one-year postpartum, together with their infant. Exposure to heat and other environmental factors will be tracked continuously through personal temperature monitors and geospatial variables at fine resolution. Our primary aim is to document linkages between heat exposure and inflammatory pathways that precede preterm birth. We will test the hypothesis that heat exposure triggers maternal inflammation by analysing epigenetic changes leading to inflammatory cytokine protein and gene expression. We also investigate the pathophysiology of thermoregulation and hydration in labour, focusing on potential protective mechanisms. Lastly, using breastmilk samples and isotope techniques, we assess whether heat exposure alters breastmilk composition and volume. Qualitative research with a sub-sample of women will explore psycho- social influences and help shape the putative pathways. Lastly, we will construct conceptual frameworks and Graphical Causal Models delineating pathways of biological vulnerability and potential protective mechanisms. Public engagement and communication underscore all study activities.