Methods: Pregnant persons living in the conterminous U.S. with geocoded residential address history data during at least 80% of their pregnancy were included. Monthly residential locations were linked to the Standardized Precipitation Evapotranspiration Index (SPEI) to assess county-specific drought conditions during pregnancy, accounting for residential moves. We used drought intensity and a binary indicator for drought (SPEI < -1.0) on the 1-month timescale to compute multiple measures of drought exposure including: any (i.e., at least one month) prenatal exposure to drought, total number of drought months, time-weighted exposure to drought, average drought intensity, trimester-specific measures of any drought and drought intensity, and drought in the month of birth.
Results: The current study included 26,534 pregnant people living in 48 states and the District of Columbia between 2000-2023. Sixty-one percent of participants were exposed to drought conditions in at least 1 month of their pregnancy, and 13% were exposed to drought during their delivery month. Participants living in the West census region and those living in a hot-dry climate region were most likely to experience drought during pregnancy (74% and 84%, respectively). Median number of drought months experienced during pregnancy ranged from 0 (Northeast) to 2 (West).
Conclusion: Understanding exposure to extreme weather among populations at higher risk of adverse events, including pregnant people, is critical. Measures of the climate related environment throughout the pregnancy rather than at one time point are essential to identify the most etiologically relevant exposure metric(s), evaluate exposure duration and intensity, and account for time-varying conditions and residential mobility.
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