When is the optimal time for delivery?--Purely from the fetuses' perspective

Area of Science:

• Perinatal Medicine
• Neonatal Outcomes
• Public Health Statistics

Background:

• Assessing the optimal gestational age for fetal transition from intrauterine to extrauterine environments is crucial for neonatal survival.
• Understanding the comparative risks of stillbirth versus neonatal death at different gestational ages informs clinical practice and policy.

Purpose of the Study:

• To identify the gestational age at which the extrauterine environment becomes safer than the intrauterine environment for fetal (neonatal) life.
• To compare stillbirth risks with early neonatal and neonatal death risks across various gestational ages.

Main Methods:

• Analysis of a large dataset of 4,896,505 livebirths, 21,222 stillbirths, and 7,513 early neonatal deaths in Japan (1989-1992).
• Gestational age-specific risk assessment for stillbirth, early neonatal death, and neonatal death.

Main Results:

• At 26 weeks gestation, neonatal death risks exceeded stillbirth risk, but these risks declined sharply by 39 weeks for singleton pregnancies.
• Stillbirth risk surpassed neonatal death risk at and beyond 40 weeks for singletons and 37 weeks for multiples.
• Optimal neonatal outcomes were observed for neonates born at 39 weeks (singleton) and 37 weeks (multiple) gestation.

Conclusions:

• The extrauterine environment offers a higher chance of survival for fetuses reaching 40 weeks (singleton) and 37 weeks (multiple) gestation in contemporary Japan.
• These findings highlight critical gestational age thresholds for neonatal survival, informing delivery timing decisions.