Mortality rates for extremely low-birthweight infants: a regional, population-based study in Japan during 2005-2009.

ABSTRACT

AIM: We investigated neonatal and infant mortality rates for extremely low-birthweight infants and clarified clinical factors associated with death. MATERIAL AND METHODS: A population-based study was conducted for 195 infants born from 2005 to 2009. RESULTS: The infant mortality rate was 28.6%, 21.7%, 34.2%, 6.7%, 6.3%, 13%, and 4.8% at 22, 23, 24, 25, 26, 28, and ≥28 weeks, respectively. The infant mortality rate according to birthweight was 50%, 9%, 31%, 16.7%, 19.4%, 7.5%, and 2.9% for <400 g, 400-499 g, 500-599 g, 600-699 g, 700-799 g, 800-899 g, and 900-999 g, respectively. Log-rank tests revealed a significant difference in the cumulative survival rates according to gestational age (P < 0.001). In the 24-week group, this rate in a tertiary center was higher than in a non-tertiary center (P = 0.001). The mortality of infants born by cesarean section (73%) was lower than that of infants born vaginally (P < 0.05). Multiple regression analyses show that the significant factors associated with death were 22-24 weeks of gestational age, management at non-tertiary centers, and multiple births. CONCLUSION: Survival of infants (<1000 g) depends on gestational age, centralization and multiple births.