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Dose-dependent relationship between acidosis at birth and likelihood of death or cerebral palsy
  1. Rod Kelly1,2,
  2. SM Ramaiah3,
  3. Helen Sheridan4,
  4. Hilary Cruickshank5,
  5. Magda Rudnicka2,
  6. Chris Kissack2,
  7. Julie-Clare Becher2,
  8. Ben J Stenson2
  1. 1Scottish Specialist Transport and Retrieval Service, Royal Infirmary of Edinburgh, Edinburgh, UK
  2. 2NHS Lothian – Neonatology, Royal Infirmary of Edinburgh, Edinburgh, UK
  3. 3The Newcastle upon Tyne Hospitals NHS Foundation Trust, Royal Victoria Infirmary, Neonatal Intensive Care Unit, Newcastle upon Tyne, UK
  4. 4NHS Lothian–Paediatrics, Royal Hospital for Sick Children, Edinburgh, UK
  5. 5NHS Lothian–Neonatal Physiotherapy, Royal Infirmary of Edinburgh, Edinburgh, UK
  1. Correspondence to Dr Rod Kelly, NHS Lothian - Neonatology, Royal Infirmary of Edinburgh, Scottish Specialist Transport and Retrieval Service, Neonatal Transport, Royal Infirmary of Edinburgh, Edinburgh, EH164SA, UK; rod.kelly{at}


Background The acid-base status of infants around birth can provide information about their past, current and future condition. Although umbilical cord blood pH <7.0 or base deficit ≥12 mmol/L is associated with increased risk of adverse outcome, there is uncertainty about the prognostic value of degree of acidosis as previous studies have used different variables, thresholds, outcomes and populations.

Methods Retrospective review of routinely collected clinical data in all live-born inborn infants of 35 weeks gestation or more delivered between January 2005 and December 2013 at the Simpson Centre for Reproductive Health, Edinburgh, UK. Infants were included if their lowest recorded pH was <7 and/or highest base deficit ≥12 mmol/L on either umbilical cord blood and/or neonatal blood gas within 1 hour of birth. Neurodevelopmental outcome of the infants with encephalopathy was collected from the targeted follow-up database.

Results 56 574 infants were eligible. 506 infants (0.9%) met inclusion criteria. Poor condition at birth and all adverse outcomes increased with worsening acidosis. Combined outcome of death or cerebral palsy was 3%, 10% and 40% at lowest pH of 6.9–6.99, 6.8–6.89 and <6.8, respectively, and 8%, 14% and 59% at a base deficit of 12–15.9, 16–19.9 and 20 mmol/L or more, respectively.

Conclusions There is a dose-dependent relationship between the degree of acidosis within an hour of delivery, and the likelihood of adverse neonatal and later neurodevelopmental outcome in infants born at 35 weeks gestation or more.

  • neonatology
  • neurodevelopment
  • acidosis
  • perinatal litigation
  • birth asphyxia

Statistics from


  • Contributors SMR and HS conducted an initial internal audit using data from 2005 to 2009 from unit admission records and patient notes. RK expanded this to a longer study period, and included data from electronic patient records (provided by CK), blood gas analysers and follow-up data (provided by HC and MR). RK wrote the manuscript under the supervision of J-CB and BJS, who both conceived and refined the study design.

  • Competing interests None declared.

  • Ethics approval South East Scotland Research Ethics Service.

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

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