European Journal of Epidemiology

, Volume 22, Issue 11, pp 791–798

Obstetrical volume and early neonatal mortality in preterm infants

  • Dorothee B. Bartels
  • Paul Wenzlaff
  • Christian F. Poets
Perinatal Epidemiology

DOI: 10.1007/s10654-007-9182-6

Cite this article as:
Bartels, D.B., Wenzlaff, P. & Poets, C.F. Eur J Epidemiol (2007) 22: 791. doi:10.1007/s10654-007-9182-6


Objective Regionalised perinatal care with antenatal transfer of high risk pregnancies to Level III centres is beneficial. However, levels of care are usually not linked to caseload requirements, which remain a point for discussion. We aimed to investigate the impact of annual delivery volume on early neonatal mortality among very preterm births. Methods All neonates with gestational age 24–30 weeks, born 1991–1999 in Lower Saxony were included into this population-based cohort study (n = 5,083). Large units were defined as caring for more than 1,000 deliveries/year, large NICUs as those with at least 36 annual very low birthweight (<1,500 g, VLBW) admissions. Main outcome criterion was mortality until day 7. Adjusted Odds Ratios (adj. OR) and 95% confidence intervals (CI) were calculated based on generalised estimating equation models, accounting for correlation of individuals within units. Results Within the first week of life, 20.6% of all neonates deceased; 10.2% were stillbirths, 3.7% died in the delivery unit, and 6.7% in the NICU. The crude OR for early neonatal mortality after having been delivered in a small delivery unit (excluding stillbirths) was 1.36 (95%CI 1.04–1.78; adj. OR 1.16 (0.82–1.63)). It increased to 1.96 (1.54–2.48; adj. OR 1.21 (0.86–1.70)) after the inclusion of stillbirths. Conclusion This study has shown a slight, but non-significant association between obstetrical volume and early neonatal mortality. In future studies the impact of caseload on outcome may become more evident when referring to high-risk patients instead of to the overall number of deliveries.


Early neonatal mortalityHospital volumePerinatal carePreterm birthQuality of care





Appropriate weight for gestational age


Confidence interval


Gestational age


General estimating equation


Large for gestational age


Missing value


Neonatal intensive care unit


Odds ratio


Respiratory distress syndrome


Small for gestational age


Very low birthweight (<1,500 g)

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Dorothee B. Bartels
    • 1
  • Paul Wenzlaff
    • 2
  • Christian F. Poets
    • 3
  1. 1.Department of Epidemiology, Public Medicine and Healthcare Systems ResearchHannover Medical SchoolHannoverGermany
  2. 2.Center for Quality and Management in Health CareHannoverGermany
  3. 3.Department of NeonatologyUniversity of TübingenTubingenGermany