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Please see: Arch Dis Child Fetal Neonatal Ed 2013;98:e1

Arch Dis Child Fetal Neonatal Ed 97:F323-F328 doi:10.1136/fetalneonatal-2011-301008
  • Original articles

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

Open Access
  1. for the Swiss Neonatal Network
  1. 1Neonatal and Paediatric Intensive Care Unit, Kinderspital Luzern, Luzern, Switzerland
  2. 2Division of Pediatric Critical Care, University of California Medical Center, San Francisco, California, USA
  3. 3Neonatal Intensive Care Unit, Universitätskinderklinik, Bern, Switzerland
  4. 4Department of Neonatology, Universitätsspital Zürich, Zurich, Switzerland
  1. Correspondence to Dr Thomas M Berger, Neonatal and Paediatric Intensive Care Unit, Kinderspital Luzern, Spitalstrasse, CH-6000 Luzern 16, Switzerland; thomas.berger{at}
  1. Contributors All of the listed authors have substantially contributed to this manuscript: conception and design, analysis and interpretation of data (TMB, MAS, MA), drafting the article (TMB, MAS) or revising it critically for important intellectual content (TMB, MAS, AW, P M-S, MA). All co-authors have approved of the final version submitted for publication.

  • Received 10 September 2011
  • Accepted 14 December 2011


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.


  • Competing interests None.

  • Ethics approval The study was approved by the National Ethics Committee and the National Expert Committee on Medical Confidentiality in Medical Research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

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