Objective: The purpose of this study was to examine characteristics associated with neonatal mortality among extremely low-birth-weight infants (< or = 1000 g).
Study design: A population-based, case-control study using linked Missouri birth and death certificates from 1989 to 1997 was conducted. Cases (n = 835) were defined as extremely low-birth-weight infants that died within 28 days of birth. Controls (n = 907) were randomly selected from extremely low-birth-weight infants that were alive at 1 year and were frequency matched to subjects by birth year and birth weight.
Results: Infants born with severe congenital anomalies and at the youngest gestational ages were at greatest risk for neonatal mortality. Other significant risk factors included maternal age (< 18 and > 34 years), vaginal delivery, nontertiary hospital care, malpresentation, male gender, and small for gestational age. Black race and preeclampsia were protective against early death.
Conclusions: The risk of neonatal mortality among extremely low-birth-weight infants was associated with several maternal, infant, and obstetric factors, some of which may be preventable.