Changing patterns of survival and outcome at 4 years of children who weighed 500–999 g at birth

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Abstract
To evaluate the impact of changing perinatal practices on survival rates and 4 year neurodevelopmental outcome for infants of birthweight 500-999 g. The study was a tertiary hospital-based prospective cohort study that compared survival, impairment and handicap rates between two eras, July 1977 to December 1982 (era 1) and January 1983 to June 1988 (era 2). All 348 live, inborn infants and 49 outborn infants of birthweight 500-999 g were prospectively enrolled in a study of survival and outcome. Rates of survival, neurodevelopmental impairment and functional handicap at 4 years were compared between eras. Perinatal risk factors for handicap were also compared between eras. Four year survival rates for inborn infants 500-999 g improved from 32.6% in era 1 to 49.2% in era 2 (OR 2.1, 95% CI 1.26-3.48) but for outborn infants the improvement between 31.8% and 53.6% was not significant. There were significant improvements in survival for inborn infants in birthweights 800-899 g and 900-999 g between study periods. The rates of functional handicap between the first and second eras (mild 10 vs 7%; severe or multiply severe 14 vs 16%) were not significantly different. Although the rate of cerebral palsy increased from 0 to 12% (P < 0.01) other rates of impairment such as blindness 0 vs 3%, deafness 2 vs 2% and developmental delay 12 vs 11% did not change. The chance of a survivor being free of handicap remained unchanged at 78% and 76% for the two eras, respectively. Although the absolute number of intact survivors more than doubled (41 vs 83) so too did the number of severe or multiply severe handicapped survivors (7 vs 17). Multivariate logistic regression analysis for the entire study cohort revealed male gender, multiple birth, prolonged mechanical ventilation and cerebral ventricular dilatation but not birthweight or gestational age to be independently associated with severe or multiply severe handicap. The advances in neonatal intensive care for extremely low birthweight infants between July 1977 and December 1982 and January 1983-June 1988 resulted in an increased number of non-disabled survivors but had no impact on incidence of severe disability. The application of prediction of mortality or severe handicap to clinical practice has the potential to reduce the proportion and absolute number of severely handicapped survivors.