Sindana D Ilango1, Meschelle Weaver2, Paige Sheridan3, Lara Schwarz3, Rachel E S Clemesha4, Tim Bruckner5, Rupa Basu6, Alexander Gershunov4, Tarik Benmarhnia7. 1. School of Public Health, San Diego State University, San Diego, CA, United States; Department of Family Medicine and Public Health, UC San Diego, La Jolla, CA, United States. Electronic address: silango@ucsd.edu. 2. Department of Family Medicine and Public Health, UC San Diego, La Jolla, CA, United States. 3. School of Public Health, San Diego State University, San Diego, CA, United States; Department of Family Medicine and Public Health, UC San Diego, La Jolla, CA, United States. 4. Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, United States. 5. Program in Public Health, UC Irvine, Irvine, CA, United States. 6. Office of Environmental Hazard Assessment, California Environmental Protection Agency, Oakland, CA, United States. 7. Department of Family Medicine and Public Health, UC San Diego, La Jolla, CA, United States; Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, United States.
Abstract
BACKGROUND: Preterm birth is a leading cause of infant morbidity and mortality. Identifying potentially modifiable triggers toward the end of gestation, such as extreme heat, can improve understanding of the role of acute stress on early deliveries and inform warning systems. In this study we examined the association between extreme heat, variously defined during the last week of gestation, and risk of preterm birth among mothers in California. METHODS: We created a population-based cohort comprised of 1,967,300 mothers who had live, singleton births in California, from May through September 2005-2013. Daily temperature data estimated at the maternal zip code of residence was used to create 12 definitions of extreme heat with varying relative temperatures (75th, 90th, 95th, and 98th percentiles) and durations (at least 2, 3, or 4 consecutive days). We estimated risk of preterm birth (<37 gestational weeks) in relation to exposure to extreme heat during the last week of gestation with multi-level Cox proportional hazard regression models, adjusting for maternal characteristics, sex of neonate, and seasonality. We also included randomly generated data, SAS code, and estimates for reproducibility purposes. RESULTS: Approximately 7% of the cohort had a preterm birth. For all definitions of extreme heat, the risk of preterm birth was consistently higher among mothers who experienced an extreme heat episode during their last week of gestation. Hazard ratios ranged from 1.008 (95% CI: 0.997, 1.021) to 1.128 (95% CI: 1.052, 1.210), with increasing associations as the relative temperature and duration of extreme heat episode increased. CONCLUSION: This study adds to the previous literature by considering multiple definitions of extreme heat and applying a time-to-event framework. Findings suggest that acute exposure to extreme heat during the last week of gestation may trigger an earlier delivery. Implementing heat warning systems targeted toward pregnant women may improve birth outcomes. Published by Elsevier Ltd.
BACKGROUND: Preterm birth is a leading cause of infant morbidity and mortality. Identifying potentially modifiable triggers toward the end of gestation, such as extreme heat, can improve understanding of the role of acute stress on early deliveries and inform warning systems. In this study we examined the association between extreme heat, variously defined during the last week of gestation, and risk of preterm birth among mothers in California. METHODS: We created a population-based cohort comprised of 1,967,300 mothers who had live, singleton births in California, from May through September 2005-2013. Daily temperature data estimated at the maternal zip code of residence was used to create 12 definitions of extreme heat with varying relative temperatures (75th, 90th, 95th, and 98th percentiles) and durations (at least 2, 3, or 4 consecutive days). We estimated risk of preterm birth (<37 gestational weeks) in relation to exposure to extreme heat during the last week of gestation with multi-level Cox proportional hazard regression models, adjusting for maternal characteristics, sex of neonate, and seasonality. We also included randomly generated data, SAS code, and estimates for reproducibility purposes. RESULTS: Approximately 7% of the cohort had a preterm birth. For all definitions of extreme heat, the risk of preterm birth was consistently higher among mothers who experienced an extreme heat episode during their last week of gestation. Hazard ratios ranged from 1.008 (95% CI: 0.997, 1.021) to 1.128 (95% CI: 1.052, 1.210), with increasing associations as the relative temperature and duration of extreme heat episode increased. CONCLUSION: This study adds to the previous literature by considering multiple definitions of extreme heat and applying a time-to-event framework. Findings suggest that acute exposure to extreme heat during the last week of gestation may trigger an earlier delivery. Implementing heat warning systems targeted toward pregnant women may improve birth outcomes. Published by Elsevier Ltd.
Entities:
Keywords:
California; Extreme heat; Heatwave; Preterm birth; Temperature
Authors: Yi Sun; Sindana D Ilango; Lara Schwarz; Qiong Wang; Jiu-Chiuan Chen; Jean M Lawrence; Jun Wu; Tarik Benmarhnia Journal: Environ Res Lett Date: 2020-10-09 Impact factor: 6.793
Authors: Yohani Dalugoda; Jyothi Kuppa; Hai Phung; Shannon Rutherford; Dung Phung Journal: Int J Environ Res Public Health Date: 2022-02-04 Impact factor: 3.390