Abstract 1449 Poster Session III, Monday, 5/3 (poster 31)

The increased survival of preterm and very low birthweight infants in recent years has been well documented by continued surveillance is required in order to monitor the effects of new therapeutic interventions. Geographically-based gestation and birthweight-specific survival rates most accurately reflect the outcome of perinatal care.

Aim: To determine survival to discharge in a large geographically-defined population of high-risk infants, to examine the effect of gender on survival and the effect of increasing postnatal age on predicted survival.

Method: Outcomes for all 19510 infants admitted to 17 NICUs throughout Canada between January 1996 and October 1997 were collected prospectively. Gestation and birthweight-specific survival for infants with birthweight <1500g or gestation <31 weeks was recorded. Actuarial survival curves were constructed to show changes in expected survival with increasing postnatal age.

Results: Complete data was available on 19019 cases (n=3710 <1500g; n=3386 <31 weeks). Survival to discharge at 24 weeks gestation was 58% compared to 82% at 26 weeks and 97% at 30 weeks. In infants with birthweight 500-599g survival to discharge was 50% compared to 80% at 700-799g and 95% at 1000-1099g. In infants born ≤24 weeks survival was higher in females but there were no significant gender differences above 24 weeks. Acturial analysis showed that expected survival improved dramatically with increasing postnatal age. For infants born at 24 weeks predicted survival to discharge was 58% at birth, 72% at 48 hours, 83% at 7 days and 92% at 4 weeks.

Conclusion: Up to date geographically-based survival rates are essential in evaluating perinatal services and monitoring the effects of new interventions. We found that the previously reported gender difference in survival is no longer apparent and speculate that the use of antenatal steroids and exogenous surfactant has diminished the survival advantage in females while improving overall survival. Actuarial analysis provides useful information when counselling parents and highlights the importance of frequently revising the prediction for long term survival particularly after the first few days of life.

Funded by the Medical Research Council of Canada