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Secular Trends in the Prevalence of Small Vulnerable Newborns in Japan, 1997-2021

Keisuke Yoshii1, Hibiki Doi1, Mizuho Igarashi1,2

  • 1Division of Endocrinology and Metabolism, National Center for Child Health and Development.

Journal of Epidemiology
|September 7, 2025
PubMed

Insights

The prevalence of small vulnerable newborns (SVNs) in Japan decreased since 2005, primarily due to fewer term small for gestational age (SGA) births. Preterm subgroups remain a concern, indicating a need for improved neonatal care strategies.

Area of Science:

  • Neonatal Health
  • Public Health
  • Epidemiology

Background:

  • The concept of small vulnerable newborns (SVNs) was introduced in 2023 to identify high-risk infants.
  • Global data on SVN prevalence is limited, necessitating regional studies.
  • Understanding SVN trends is crucial for developing effective preventive strategies.

Purpose of the Study:

  • To analyze secular trends in the prevalence of SVNs and their subgroups in Japan.
  • To investigate the prevalence of term small for gestational age (SGA), preterm SGA, and preterm non-SGA infants.
  • To explore potential associations between SVN prevalence and medical resource distribution.

Main Methods:

  • Analysis of Japanese vital statistics data from 1997 to 2021, including livebirths and stillbirths.
  • Assessment of secular trends in the overall SVN population and specific subgroups.
  • Regional analysis to examine the relationship between SVN prevalence and medical resource distribution.

Main Results:

  • A total of 26,172,760 newborns were analyzed.
  • Overall SVN prevalence decreased from 7.8% in 1997 to 7.7% in 2021, peaking at 8.7% in 2005.
  • The decline was driven by reduced term SGA births; preterm SGA and preterm non-SGA rates remained stable.

Conclusions:

  • SVN prevalence in Japan has declined, largely due to a decrease in term SGA births.
  • Persistent high rates in preterm subgroups emphasize the ongoing challenge of prematurity.
  • Targeted interventions are essential to improve neonatal outcomes for vulnerable preterm infants.
Abstract

Keywords:
Japanpretermsecular trendsmall for gestational agesmall vulnerable newborn

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