Changing long-term outcomes for infants 500-999 g birth weight in Victoria, 1979-2005

Objective To determine the survival and neurological outcome at 2 years of age of extremely low birthweight (ELBW, birth weight 500-999 g) infants born in the state of Victoria compared with term controls, and contrasted with ELBW cohorts from previous eras. Design and setting A population-based cohort study of consecutive ELBW infants born during 2005 in the state of Victoria, and also in 1979-1980, 1985-1987, 1991-1992 and 1997. Participants All 257 live births free of lethal malformations weighing 500-999 g in 2005, 220 randomly selected term, normal birthweight (birth weight >2499 g) controls, and equivalent cohorts born in earlier eras. Main outcome measures Survival rates and quality-adjusted survival rates at 2 years of age, contrasted between cohorts. Results Of 257 ELBW live births in 2005, 66.9% survived to 2 years of age, significantly lower than the survival rate of 75.2% for 1997 (odds ratio (OR) 0.67, 95% CI 0.45 to 0.99, p=0.046), but not after adjustment for confounders of birth weight, gestational age and gender (adjusted OR 0.73, 95% CI 0.46 to 1.16, p=0.18). This was a reversal of the steady increase in survival rates up to 1997. Rates of blindness, severe developmental delay and severe disability were significantly lower in 2005 than in ELBW survivors from previous eras. Consequently the difference in the quality-adjusted survival rates between 2005 and 1997 was only -3.8% (95% CI -11.4% to 3.7%, p=0.32). Conclusions Regional survival rates for ELBW infants have plateaued since the late 1990s, but the neurosensory outcome in survivors has improved in 2005.