Trends in morbidity and mortality among very-low-birth-weight infants from 2003 to 2008 in Japan

Pediatr Res. 2012 Nov;72(5):531-8. doi: 10.1038/pr.2012.114. Epub 2012 Aug 24.


Background: Although medical care for very-low-birth-weight (VLBW) infants has improved over time, it is unclear how this has affected mortality and morbidity. To characterize these trends, a network database was analyzed.

Methods: This is a cohort study of VLBW infants born from 2003 through 2008.

Results: Over the 6-y period, 19,344 infants were registered and analyzed. Crude mortality rates among the infants at discharge decreased significantly (from 10.8 to 8.7%) during the study period. The greatest improvement in mortality was observed among infants with birth weights between 501 and 750 g (25.6-17.7 %). The odds ratio (OR) of mortality over year adjusted for potential confounders by a logistic regression model was 0.94 (95% confidence interval 0.92-0.97). Significant increases were observed in some morbidities, including symptomatic patent ductus arteriosus with an OR of 1.11 (1.09-1.13); late-onset adrenal insufficiency, 1.21 (1.17-1.26); and necrotizing enterocolitis/intestinal perforation, 1.10 (1.01-1.12). However, the severe form of intraventricular hemorrhage, with an OR of 0.98 (0.92-0.99), decreased significantly. Risk-adjusted trends in other morbidities showed no significant change.

Conclusion: Mortality of VLBW infants decreased significantly over the 6-y study period. Decreasing morbidity is essential for further improvement in the outcomes in VLBW infants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Birth Weight*
  • Cause of Death
  • Chi-Square Distribution
  • Gestational Age
  • Hospital Mortality / trends*
  • Hospitals / trends
  • Humans
  • Infant Mortality / trends*
  • Infant, Newborn
  • Infant, Newborn, Diseases / mortality*
  • Infant, Newborn, Diseases / therapy
  • Infant, Premature*
  • Infant, Very Low Birth Weight*
  • Intensive Care Units, Neonatal / trends
  • Japan / epidemiology
  • Logistic Models
  • Multivariate Analysis
  • Odds Ratio
  • Prognosis
  • Registries
  • Retrospective Studies
  • Risk Factors
  • Time Factors