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 approximately 1 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 era 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.