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

Abstract

In Japan, the mortality rate of extremely low birth weight (ELBW) infants is notably low among the 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 the neonatal intensive care units (NICUs) in Japan and to examine the factors that affect the short-term outcome of these infants. We also compared the mortality of ELBW infants born in 2005, 2010, and 2015. We analyzed the mortality, morbidity, and factors related to short-term outcomes of ELBW infants, using data of 2,782 infants born in 2015 registered at the NICUs in Japan. Mortality rate during NICU stay was 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 birth weight 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 any treatment was observed in 30.4%. Mortality in ELBW infants decreased significantly from 2005 to 2015. As CLD and ROP may affect the 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.