DELIVERY X ATMOS PRES DROPS X Sudden drops in atmospheric pressure (e.g., typhoons, hurricanes) correlate with an increase in spontaneous-onset deliveries.

 A

Summary Bullet Points

• Workload & Complications: Fluctuations in daily delivery volume impact obstetricians' workload and maternal–fetal outcomes.

• Weather Influence: Sudden drops in atmospheric pressure (e.g., typhoons/hurricanes) may increase daily delivery volume in the following days.

• Objective: Investigated the association between atmospheric pressure drops and spontaneous-onset deliveries, considering gestational age and lagged effects.

• Methods:

  • Time-stratified case-crossover design using Japan Perinatal Registry Network data (2011–2020).

  • Analyzed 1,074,380 spontaneous-onset deliveries across 47 prefectures.

  • Quasi-Poisson regression with distributed lag nonlinear models (lag: up to 14 days).

  • Meta-analysis combined prefectural estimates; stratified by gestational week (<37, 37, 38, 39, 40, 41+ weeks).

• Results:

  • Delivery volume increase peaked within 0–4 days after a pressure drop, diminishing after 1 week.

  • Strongest associations at 38–40 weeks gestation:

    • 38 weeks: Relative risk (RR) = 1.07 (95% CI 1.00–1.14)

    • 39 weeks: RR = 1.08 (95% CI 1.02–1.14)

    • 40 weeks: RR = 1.10 (95% CI 1.03–1.19)

• Conclusions: Pressure drops were associated with a modest increase in spontaneous-onset deliveries, particularly at full-term gestation.

A