A prospective study of heat exposure and miscarriage

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ABSTRACT Given the scientific consensus regarding the role of climate change in causing increased temperatures and higher frequency of extreme weather events in the coming decades, it is crucial to clarify the effects of climate change on human reproduction. A substantial body of research has documented that exposure to heat is associated with adverse pregnancy and neonatal outcomes, including preeclampsia, gestational hypertension, low birth weight, and preterm birth. However, there has been limited assessment of the association between ambient heat and spontaneous abortion (SAB), defined as a pregnancy loss before 20 weeks’ gestation. SAB is a particularly challenging reproductive event to measure because many SABs occur early in gestation, often before pregnancy recognition. The ideal study design for accurately measuring SAB is a preconception cohort where early reproductive events are closely monitored. In addition, most research on the health effects of heat have measured ambient rather than personal temperature exposure, despite the fact that ambient temperature does not sufficiently represent the environmental conditions individuals experience as they move throughout time and space. In the present proposal, we will utilize the infrastructure of an ongoing preconception cohort study, Pregnancy Study Online (PRESTO), to explore the role of ambient and personal heat exposure in the etiology of SAB. PRESTO has successfully enrolled a geographically, racially, and socioeconomically diverse cohort of couples trying to conceive from across the United States and Canada, and using these data, we have prospectively identified SAB, including early SAB (<6 weeks’ gestation), and assessed risk factors for SAB. Specifically, in the present proposal, we aim to 1) examine the association between ambient heat and SAB risk and measure the extent to which select geospatial features mediate or modify this association, and 2) deploy wearable personal temperature monitors for one week among 400 newly-enrolled female PRESTO participants and use monitoring data to identify geospatial, neighborhood, and individual-level predictors of heat exposure. The proposed study will have a large and sustained impact on the fields of reproductive epidemiology and climate health. This will be the first study to measure personal exposure to heat in pregnant women, a population with underlying physiologic susceptibility to heat. Our predictive models of heat exposure have vast applications in fields of environmental exposure assessment. The ability to measure personal heat exposure using questionnaire and geospatial data, rather than relying on personal monitoring, could revolutionize the study of the health effects of extreme temperatures. In addition, this study could provide critical information on the etiology of SAB, inform specific interventions to reduce SAB risk, and challenge current clinical practice guidelines for advising women early in pregnancy that focus on lifestyle factors such as smoking and diet. Finally, we seek to shift current research paradigms by advancing knowledge on the role of climate change in shaping reproductive outcomes.