VERY-LOW-BIRTH-WEIGHT OUTCOMES OF THE AL-INSTITUTE-OF-CHILD-HEALTH-AND-HUMAN-DEVELOPMENT NEONATAL RESEARCH NETWORK, MAY 1991 THROUGH DECEMBER 1992

OBJECTIVES: Our goals were to determine the mortality risk for infants weighing 501 to 1500 gm according to gestational age, birth weight, a nd gender and to document birth weight-related changes in mortality an d morbidity over a 5-year time period. STUDY DESIGN: In this observati onal study perinatal data were prospectively collected by the 12 parti cipating centers of the National Institute of Child Health and Human D evelopment Neonatal Research Network from May 1991 through December 19 92 and compared with the corresponding data from 1987 through 1990. St andard definitions were used to record sociodemographic factors, perin atal events, and the neonatal course to 120 days of life, discharge, o r death. RESULTS: The 1991 and 1992 cohort included 4279 in-born infan ts. Among their mothers 10% were <18 years old; 55% were black, 31% we re white, and 11% were Hispanic; 14% had received no prenatal care; an d 20% had received antenatal corticosteroids. Multiple gestations acco unted for 20% of the births. Fifty percent of the infants were deliver ed by cesarean section. During 1991 and 1992 the overall survival for infants weighing 501 to 1500 gm at birth was 81%, compared with 74% in 1987 and 1988. Survival at birth weight 501 to 750 gm was 44%; it was 81% at 751 to 1000 gm, 92% at 1001 to 1250 gm, and 95% between 1251 a nd 1500 gm. Female infants had a significantly greater chance of survi ving than male infants at similar birth weights and gestational ages. At any given gestational age, smaller infants were less likely to surv ive. Survival in all birth weight categories increased between 1987 an d 1992, without accompanying increases in medical morbidity. Major mor bidity increased with decreasing birth weight and included late-onset septicemia 22%, chronic lung disease (oxygen dependence at 36 weeks' c orrected age) 18%, severe intraventricular hemorrhage (grades III and IV) 11%, and necrotizing enterocolitis 5%. Twelve percent of all infan ts were treated with corticosteroids for chronic lung disease, includi ng 36% of infants who were oxygen dependent at age 28 days. The mean l ength of hospital stay was 69 days for survivors and 18 days for infan ts who died. CONCLUSIONS: Mortality for infants between 501 and 1500 g m at birth has declined over the past 5 years. There are interactions between birth weight, gestational age, gender, and survival rate. This increase in survival was not accompanied by an increase in medical mo rbidity.