Mortality and morbidity of extremely low birth weight infants in Japan, 2015

Tokuo Miyazawa, Hitomi Arahori, Satoshi Ohnishi, Hromichi Shoji, Atsushi Matsumoto, Yuka Sano Wada, Naoto Takahashi, Toshimitsu Takayanagi, Satoshi Toishi, Ken Nagaya, Hisaya Hasegawa, Masahiro Hayakawa, Mariko Hida, Rie Fukuhara, Yasumasa Yamada, Masahiko Kawai, Kusaka Takashi, Kazuko Wada, Ichiro Morioka, Katsumi Mizuno

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


BACKGROUND: In Japan, the mortality rate of extremely low birth weight (ELBW) infants is notably low in comparison with other developed countries, but the prevalence of chronic lung disease (CLD) and retinopathy of prematurity (ROP) is relatively high. This study aimed to estimate the mortality and morbidity of ELBW infants born in 2015 who were admitted to neonatal intensive care units (NICUs) in Japan and to examine the factors that affected the short-term outcomes of these infants. We also compared the mortality of ELBW infants born in 2005, 2010, and 2015. METHODS: We analyzed the mortality, morbidity, and factors related to short-term outcomes of ELBW infants, using data from 2782 infants born in 2015 and registered at NICUs in Japan. RESULTS: The mortality rates during NICU stays were 17.0%, 12.0%, and 9.8% for ELBW infants born in 2005, 2010, and 2015, respectively. Among ELBW infants born in 2015, multiple logistic regression analysis showed that short gestational age and low birthweight Z-score contributed to the increased risk of death. Births by cesarean section and antenatal corticosteroid administration were significantly associated with a reduced risk of death. Among infants who survived, CLD was observed in 53.1% and ROP requiring treatment was observed in 30.4%. CONCLUSIONS: Mortality in ELBW infants decreased significantly from 2005 to 2015. As CLD and ROP may affect quality of life and long-term outcomes of infants who survived, prevention strategies and management for these complications are critical issues in neonatal care in Japan.

Original languageEnglish
Pages (from-to)e15493
JournalPediatrics International
Issue number1
Publication statusPublished - 2023 Jan 1


  • antenatal corticosteroid
  • cesarean section
  • extremely low birthweight infant
  • morbidity
  • mortality

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


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