Research on the impact of heat on pregnant women has focused largely on outcomes following extreme temperature events, such as particular heat waves or spells of very cold weather on pregnant women. Consistently, the literature has shown a statistically significant relationship between heat with shortened gestational age with studies concentrated largely in the western states of the USA or other nations. The association between heat and shortened gestational age has not been examined in the Southeastern US where maternal outcomes are some of the most challenging in the nation. Unlike previous studies that focus on the impacts of a single heat wave event, this study seeks to understand the impact of high heat over a 5-year period during the annual warm season (May–September). To achieve this goal, a case-crossover study design is employed to understand the impact of heat on preterm labor across regions in North Carolina (NC). Temperature thresholds for impact and the underlying relationships between preterm labor and heat are investigated using generalized additive models (GAM). Gridded temperature data (PRISM) is used to establish exposure classifications. The results reveal significant impacts to pregnant women exposed to heat with regional variations. The exposure variable with the most stable and significant result was minimum temperature, indicating high overnight temperatures have the most impact on preterm birth. The magnitude of this impact varies across regions from a 1% increase in risk to 6% increase in risk per two-degree increment above established minimum temperature thresholds.
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The authors would like to acknowledge Jess Rinsky, PhD, MPH, Epidemiologist, Division of Public Health, Occupational and Environmental Epidemiology Branch, NC Department of Health and Human Services for her consultation and guidance on this project.
Conflict of interest
The authors declare that they have no conflict of interest.
CISA is a pilot program of the NOAA National Integrated Heat Health Information System (NIHHIS).
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Ward, A., Clark, J., McLeod, J. et al. The impact of heat exposure on reduced gestational age in pregnant women in North Carolina, 2011–2015. Int J Biometeorol 63, 1611–1620 (2019). https://doi.org/10.1007/s00484-019-01773-3
- Climate-health vulnerabilities
- Maternal health