Conditional survival rate of very-low-birth-weight (VLBW) infants in a tertiary medical center

Background: Very-low-birth weight (VLBW) infants, defined as those with a birth body weight (BBW) < 1,501 g, are at high risk for mortality. Compared to the traditional survival rate, which simply reflects the overall survival rate, the conditional survival rate provides the future life expectancy at a given postnatal age and is more practical clinically. This study explores and compares the conditional survival rate and traditional survival rate of VLBW infants in a tertiary medical center. Methods: Two-hundred and eighty-eight VLBW infants admitted to the neonatal intensive care unit (NICU) of a tertiary medical center were enrolled. Patients were stratified by BBW in 100 g intervals and gestational age (GA) in weekly intervals. The conditional survival rate and traditional survival rate were calculated for both stratification methods. Results: The overall survival rate was 80.6%. More than half of all deaths (53.5%) occurred in the first week of life. The conditional survival rate increased rapidly after the first week of life. The most profound increments were infants with BBW < 700 g and GA < 27weeks. Conclusions: The conditional survival rate is more useful than the traditional survival rate in respect to future life expectancy in VLBW infants especially for small and immature infants.