Trends and centre-to-centre variability in survival rates of very preterm infants (<32 weeks) over a 10-year-period in Switzerland.

Background: The publication of Swiss guidelines for the care of infants at the limit of viability (22-25 completed weeks) was followed by increased survival rates in the more mature infants (25 completed weeks). At the same time, considerable centre-to-centre (CTC) differences were noted.

Objectives: To examine the trend of survival rates of borderline viable infants over a 10-year-period and to further explore CTC differences.

Design: Population-based, retrospective cohort study.

Setting: All nine level III neonatal intensive care units (NICUs) and affiliated paediatric hospitals in Switzerland.

Patients: 6532 preterm infants with a gestational age (GA) <32 weeks born alive between 1 January 2000 and 31 December 2009.

Main Outcome Measures: Trends of GA-specific delivery room and NICU mortality rates and survival rates to hospital discharge were assessed. For CTC comparisons, centre-specific risk-adjusted ORs for survival were calculated in three GA groups: A: 23 0/7 to 25 6/7 weeks (n=976), B: 26 0/7 to 28 6/7 weeks (n=1943) and C: 29 0/7 to 31 6/7 weeks (n=3399).

Results: Survival rates of infants with a GA of 25 completed weeks which had improved from 42% in 2000/2001 to 60% in 2003/2004 remained unchanged at 63% over the next 5 years (2005-2009). Statistically significant CTC differences have persisted and are not restricted to borderline viable infants.

Conclusions: In Switzerland, survival rates of infants born at the limit of viability have remained unchanged over the second half of the current decade. Risk-adjusted CTC outcome variability cannot be explained by differences in baseline demographics or centre case loads.