What does this research mean for the field?

Exposure to both extreme heat and cold during late pregnancy increases the risk of preterm birth, and while heat-related risk declined slightly before 2011, it has since plateaued, indicating limited recent adaptation. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This research investigates the relationship between ambient temperature exposure in late pregnancy and the risk of preterm birth in Japan over several decades.

June 6, 2026The Lancet Regional Health - Western PacificOpen Access

Temporal trends in late-pregnancy exposure to ambient temperature and risk of preterm birth in Japan, a nationwide study from 1979 to 2023

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Authors

ACAlton CaoDepartment of Health LYLei YuanThe University of Tokyo SISophearen IthNational Institute of Infectious Diseases

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Implication

Nationwide study assesses heat and cold exposure effects on preterm birth risk in Japan, indicating limited adaptation over decades.

Key Points

This research investigates the relationship between ambient temperature exposure in late pregnancy and the risk of preterm birth in Japan over several decades.
Conducted a nationwide study using time-stratified case-crossover and conditional Poisson models from 1979 to 2023.
Implemented a 28-day distributed lag non-linear model along with mixed-effects meta-regression for analyzing prefecture-level data.
Pooled prefecture-specific estimates using random-effects meta-analysis to determine temporal changes in susceptibility.
Identified a 1.13 relative risk (RR) for preterm birth associated with high temperatures (99th percentile) and 1.11 for low temperatures (1st percentile).
Attributed 4.7% of total preterm births nationally to non-optimal temperatures, with 1.9% due to heat and 2.8% from cold.
Noted a decline in heat-related RR from 1.16 in 1979-1989 to 1.07 in 2001-2011, with cold-related risks remaining stable.

Cite This Study

Cao et al. (2026) studied this question.

synapsesocial.com/papers/6a23ba8771a5da9775e763ab https://doi.org/10.1016/j.lanwpc.2026.101894

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Temporal trends in late-pregnancy exposure to ambient temperature and risk of preterm birth in Japan, a nationwide study from 1979 to 2023

Discussion

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Implication

Key Points

Cite This Study

Temporal trends in late-pregnancy exposure to ambient temperature and risk of preterm birth in Japan, a nationwide study from 1979 to 2023

Discussion

Member takes

Implication

Key Points

Cite This Study

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