Day-by-day postnatal survival in very low birth weight infants

Abstract

Objectives: Postnatal survival rates of very low birth weight (VLBW) infants are well established for each birth weight or gestational age category. These figures do not differentiate viable infants who survive the first few days of life from extremely immature ones who die shortly after birth. This study aimed to develop standardized curves for day-by-day postnatal survival rates of VLBW infants.

Methods: National Inpatient Sample Database and its pediatrics-only subportion were analyzed for the years 1997-2004. Infants with birth weight <1500 g were included in the study. Infants were classified according to their birth weight into 4 groups: <500, 500 to 749, 750 to 999, and 1000 to 1499 g. Postnatal survival rates were calculated for each group at birth and at 1, 2, 3, 4 to 5, 6 to 7, 14, 21, 28, and >28 postnatal days.

Results: Overall survival for infants with birth weight <500 g was 8%. Those who lived through the first 3 days of life had a chance of survival up to 50%. Infants in the 500- to 749-g group had overall survival rate of 50% that increased to 70% if they survived through the third day and 80% by the end of the first week. There was no improvement in the overall survival of any birth weight category over the years of the study.

Conclusions: VLBW infants who survive the first few postnatal days have a considerably better chance for life. We can predict postnatal survival chances for each birth weight category on a day-by-day basis until discharge.