Objective To characterise the actuarial day-by-day survival of premature infants in a geographically defined population.

Setting 10 Neonatal Intensive Care Units (NICUs) in New South Wales (NSW) and Australian Capital Territory (ACT), Australia.

Design Retrospective analysis of prospectively collected data as part of NICUs' data collection in NSW and ACT.

Subjects Premature infants born at 22⁺⁰ to 31⁺⁶ weeks' gestation between January 1997 and December 2006 and admitted to one of the 10 NICUs in NSW and ACT.

Outcome Actuarial day-by-day survival to discharge from NICU.

Results Survival to discharge after initiation of neonatal intensive care ranges from 30.0% at 23 weeks' gestation to 98.8% at 31 weeks. Actuarial day-by-day survival increased across all gestations. This improvement was most notable among the babies who were born <26 weeks gestation.

Conclusion Preterm infants who survive the first few postnatal days have considerable chances of long-term survival. It is important to revise the information stored regarding chances of survival so it covers chances at regular intervals, especially after the first few days of life.