Objective: To determine the survival and sensorineural disability rates in very preterm infants born in 1991-92, and to compare the results with contemporaneous normal birthweight controls and with preterm infants born in 1985-87.
Methodology: This was a geographically determined cohort study in the state of Victoria, Australia of consecutive livebirths 23-27 weeks' gestational age born during 1991-92, and randomly selected contemporaneous normal birthweight (NBW) controls born during 1991-92 in the three level-III perinatal centres in the State. Consecutive livebirths 24-26 weeks gestational age born in the State during 1985-87 comprised another comparison group. The main outcome measures were survival and sensorineural disability rates at 2 years of age.
Results: Of the 401 livebirths 23-27 weeks in 1991-92, 225 (56.1%) survived to 2 years of age. The survival rate for those 24-26 weeks was 57.4% (143/249), a statistically significant increase on the regional survival rate of 30.1% (95/316) in 1985-87. In 1991-92 births, the survival rate rose significantly with increasing gestational age, and was significantly higher than in 1985-87 at each of 24, 25, and 26 weeks. Of sensorineural impairments in preterm survivors at 2 years of age, the rate of blindness was significantly lower in 1991-92 (2.3%) compared with 1985-87 (8.4%), and the overall rates of sensorineural disability were not statistically different in 1991-92 compared with 1985-87. In 1991-92 preterm survivors, the survival rate free of disability rose significantly with increasing gestational age, and as a percentage of survivors the rate of disability overall fell with increasing gestational age. However, the rate of disability overall was much higher in preterm infants than NBW controls.
Conclusions: Survival rates of very preterm infants in this regional cohort have improved in the 1990s after the introduction of exogenous surfactant. Blindness at 2 years of age was significantly lower than in an earlier preterm cohort, but the rates of sensorineural disability still remain higher in very preterm survivors than for NBW controls. Although survival rates are lower and disability rates are higher with diminishing maturity, there is no obvious gestational age below which adverse neurological outcome in survivors would preclude active management on the basis of gestational age alone.