Evidence suggests that heat exposure increases delivery risk for pregnant women. Acceleration of childbirth leads to shorter gestation, which has been linked to later health and cognitive outcomes. However, estimates of the aggregate gestational losses resulting from hot weather are lacking in the literature. Here, we use estimated shifts in daily county birth rates to quantify the gestational losses associated with heat in the United States from 1969 to 1988. We find that extreme heat causes an increase in deliveries on the day of exposure and on the following day and show that the additional births were accelerated by up to two weeks. We estimate that an average of 25,000 infants per year were born earlier as a result of heat exposure, with a total loss of more than 150,000 gestational days annually. Absent adaptation, climate projections suggest additional losses of 250,000 days of gestation per year by the end of the century.
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All data necessary for replication of the results in this paper are available for download at https://figshare.com/s/c984d29316e012b79e32. The original weather data can be downloaded from ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/daily. The original birth records can be downloaded from http://www.nber.org/natality/. The population data can be downloaded from https://seer.cancer.gov/popdata/download.html. Interested researchers should contact Urs Beyerle or Jan Sedlacek at ETH Zurich to gain access to the CMIP5 climate projection data. Source data for Figs. 1–4 are provided with the paper.
The code necessary for replication of the results in this paper is available for download at https://figshare.com/s/c984d29316e012b79e32.
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We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups for producing and making available their model output. We are grateful for U. Beyerle and J. Sedlacek at ETH Zurich, who provided access to the CMIP data. This research was supported by funding from the California Strategic Growth Council Climate Change Research Program (no. CCRP0056). P. Stainier provided valuable research assistance.
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Figs. 1–4.
Source Data Fig. 1
Temperature-Dose Response Function on Day 0
Source Data Fig. 2
Effect of Daily Maximum Temperature ≥90 °F on Birth Rates, by Days from Exposure. a: Distributed lag coefficients; b: cumulative effects
Source Data Fig. 3
Heterogeneous Effects of Daily Max Temperature ≥90 °F on Birth Rates
Source Data Fig. 4
Modifying effect of air conditioning
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Barreca, A., Schaller, J. The impact of high ambient temperatures on delivery timing and gestational lengths. Nat. Clim. Chang. 10, 77–82 (2020). https://doi.org/10.1038/s41558-019-0632-4
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