Peer-reviewed article
Secular Trends in the Prevalence of Small Vulnerable Newborns in Japan, 1997-2021.
Yoshii K, Doi H, Igarashi M, Ogawa K, Matsubara K et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined trends in the prevalence of small vulnerable newborns (SVNs) in Japan from 1997 to 2021 using vital statistics data on over 26 million births. The overall prevalence of SVNs declined from 8.7% in 2005 to 7.7% by 2021, driven primarily by fewer term small-for-gestational-age births. However, preterm births—both small and normal-sized—remained at stable, persistently high rates, indicating ongoing challenges in preventing prematurity. The study found no link between regional medical resources and SVN prevalence variation.
Key points
- Overall SVN prevalence peaked at 8.7% in 2005 and declined to 7.7% by 2021
- The decline was primarily due to reduced term SGA births (falling to 2.0% by 2021)
- Preterm SGA (0.44%) and preterm non-SGA (5.3%) prevalence remained largely unchanged over the period
- No significant association found between regional distribution of medical resources and SVN prevalence variation
- Study included 26,172,760 livebirths and stillbirths across the 25-year period
Limitations
This is a descriptive epidemiological study using vital statistics data, so it cannot determine the causes of the trends observed or evaluate specific interventions to reduce SVN prevalence. Regional analysis cannot explain why medical resource distribution does not correlate with SVN outcomes.
Abstract
Background In 2023, a collaborative United Nations Children's Fund-World Health Organization group introduced the concept of small vulnerable newborns (SVNs) to improve the identification of newborns at increased risk of adverse outcomes and to guide more effective preventive strategies. However, global data on the prevalence of SVNs remains scarce. This study aimed to examine secular trends in the prevalence of SVNs and their three subgroups, namely term small for gestational age (SGA), preterm SGA, and preterm non-SGA, in the Japanese population. Methods We analyzed data from vital statistics including livebirths and stillbirths between 1997 and 2021. Secular trends in the prevalence of SVNs and their subgroups were assessed. In addition, we conducted regional analyses to explore associations with the distribution of medical resources. Results A total of 26,172,760 newborns were included. The overall prevalence of SVNs was 7.8% in 1997, peaked at 8.7% in 2005, and declined to 7.7% by 2021. This decline was primarily attributed to a reduction in term SGA births. In contrast, the prevalence of preterm SGA and preterm non-SGA remained largely unchanged. In 2021, the prevalence of term SGA, preterm SGA, and preterm non-SGA was 2.0%, 0.44%, and 5.3%, respectively. No significant association was found between the regional variation in the prevalence of SVNs and the distribution of medical resources. Conclusion The prevalence of SVNs in Japan has declined since 2005, mainly due to reduced term SGA births. Persistent rates of preterm subgroups highlight the ongoing burden of prematurity, underscoring the need for targeted strategies to improve neonatal outcomes.