Evaluation of neonatal intensive care for extremely low birth weight infants in Victoria over two decades: I. Effectiveness

Context. Although individual components of neonatal intensive care have proven efficacy, doubts remain about its overall effectiveness. Objective. To determine the changes in effectiveness of neonatal intensive care for extremely low birth weight (ELBW) infants over 2 decades. Design. Population-based cohort study of consecutive ELBW infants born during 4 distinct eras: 1979-1980, 1985-1987, 1991-1992, and 1997, all followed to at least 2 years of age. Setting. The state of Victoria, Australia. Patients. All ELBW live births of birth weight 500 to 999 g in the state in the calendar years indicated (1979 1980 [n = 351]; 1985-1987 [n = 560]; 1991-1992 [n = 429]; 1997 [n = 233]). Survivors were assessed at 2 years of age by pediatricians and psychologists blinded to perinatal details. The follow-up rates were high for each ELBW cohort (1979-1980: 100% [89 of 89]; 1985-1987: 100% [212 of 212]; 1991-1992: 98% [237 of 241]; 1997: 99% [168 of 170]). Main Outcome Measures. Survival and quality-adjusted survival rates at 2 years of age. Results. The survival rate to 2 years of age improved significantly between successive eras (absolute increase and 95% confidence interval: 1985-1987 vs 1979-1980, 12.5% and 6.3%-18.4%; 1991-1992 vs 1985-1987, 18.3% and 12.1%-24.4%; 1997 vs 1991-1992, 16.8% and 9.2%-23.9%), as did the quality-adjusted survival rate (absolute increase: 1985-1987 vs 1979-1980, 12.4%; 1991-1992 vs 1985-1987, 13.8%; 1997 vs 1991-1992, 13.2%). Overall, the survival rate increased from similar to1 in 4 (25%) in 1979-1980 to 3 in 4 (73%) in 1997, and the quality-adjusted survival rate also increased threefold, from 19% in 1979 - 1980 to 59% in 1997. The biggest gains in survival and quality-adjusted survival in the most recent area were in infants in lighter birth-weight subgroups. Conclusion. The effectiveness of neonatal intensive care for ELBW infants in Victoria improved progressively from the late 1970s to the late 1990s.