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Intrapartum risk factors for newborn encephalopathy: the Western Australian case-control study

BMJ 1998; 317 doi: https://doi.org/10.1136/bmj.317.7172.1554 (Published 05 December 1998) Cite this as: BMJ 1998;317:1554
  1. Nadia Badawi, neonatologist (nadiaB{at}nch.edu.au)a,
  2. Jennifer J Kurinczuk, epidemiologista,
  3. John M Keogh, obstetricianb,
  4. Louisa M Alessandri, senior research officera,
  5. Fiona O'Sullivan, research midwifea,
  6. Paul R Burton, senior biostatisticianc,
  7. Patrick J Pemberton, neonatologistd,
  8. Fiona J Stanley, directora
  1. TVW Telethon Institute for Child Health Research, PO Box 855, West Perth, Western Australia 6872, Australia
  2. Department of Obstetrics and Gynaecology, Hornsby Ku-ring-Gai Hospital, Hornsby, New South Wales 2077, Australia
  3. Department of Paediatrics, University of Western Australia, Western Australia 6907, Australia
  4. Princess Margaret Hospital for Children, Subiaco, WA 6008, Australia
  1. aCorrespondence to: Dr N Badawi, Department of Neonatology, New Children's Hospital, Royal Alexandra Hospital for Children, PO Box 3515, Parramatta, New South Wales, New South Wales 2124, Australia
  • Accepted 5 December 1998

Abstract

Objective: To identify intrapartum predictors of newborn encephalopathy in term infants.

Design: Population based, unmatched case-control study.

Setting: Metropolitan area of Western Australia, June 1993 to September 1995.

Subjects: All 164 term infants with moderate or severe newborn encephalopathy; 400 randomly selected controls.

Main outcome measures: Adjusted odds ratio estimates.

Results: The birth prevalence of moderate or severe newborn encephalopathy was 3.8/1000 term live births. The neonatal fatality was 9.1%. Maternal pyrexia (odds ratio 3.82), a persistent occipitoposterior position (4.29), and an acute intrapartum event (4.44) were all risk factors for newborn encephalopathy. More case infants than control infants were induced (41.5% and 30.5%, respectively) and fewer case infants were delivered by caesarean section without labour (3.7% and 14.5%, respectively). Operative vaginal delivery (2.34) and emergency caesarean section (2.17) were both associated with an increased risk. There was an inverse relation between elective caesarean section (0.17) and newborn encephalopathy. After application of a set of consensus criteria for elective caesarean section only three (7%) eligible case mothers compared with 33 (65%) eligible control mothers were sectioned electively. Of all the case infants, 113 (69%) had only antepartum risk factors for newborn encephalopathy identified; 39 (24%) had antepartum and intrapartum factors; eight (5%) had only intrapartum factors; and four (2%) had no recognised antepartum or intrapartum factors.

Conclusions: The causes of newborn encephalopathy are heterogeneous and many relate to the antepartum period. Elective caesarean section has an inverse association with newborn encephalopathy. Intrapartum hypoxia alone accounts for only a small proportion of newborn encephalopathy. These results question the view that most risk factors for newborn encephalopathy lie in the intrapartum period.

Footnotes

    • Accepted 5 December 1998
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