title: The relationship between umbilical cord arterial pH and serious adverse neonatal outcome: analysis of 51,519 consecutive validated samples.
abstract: OBJECTIVE
  To examine the relationship between umbilical cord pH at term and serious neonatal outcomes.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  Deliveries within the Oxford Radcliffe Hospital NHS Trust between 1991 and 2009.
  
  
  METHODS
  In all, 51,519 singleton, term, nonanomalous live neonates with validated umbilical cord arterial pH values.
  
  
  METHODS
  Absolute risks, relative risks with 95% confidence intervals, and numbers needed to harm were calculated for different levels of arterial pH across the entire range.
  
  
  METHODS
  Neonatal encephalopathy with seizures and/or death, encephalopathy within 24 hours of birth, 5-minute Apgar scores and neonatal unit admission.
  
  
  RESULTS
  The median arterial pH was 7.22, interquartile range 7.17-7.27. The absolute risk of an adverse neurological outcome was significantly increased below 7.10 (0.36%) and was lowest between 7.26 and 7.30 (0.16%). Even below 7.00, the risk was only 2.95%. However, more than 75% of neonates with neurological outcomes examined, including seizures within 24 hours of birth, had a pH above 7.10. A small increase in risk was evident at higher pH levels.
  
  
  CONCLUSIONS
  The threshold pH for adverse neurological outcomes is 7.10 and the 'ideal' cord pH is 7.26-7.30. Above 7.00, however, neonatal acidaemia is weakly associated with adverse outcomes. Most neonates with neurological morbidity have normal cord pH values. Other variables must influence adverse outcomes and account for more of these than acidaemia. A better understanding of these is required before intrapartum fetal monitoring can improve.
authors.affiliation: Oxford Fetal Medicine Unit, The Women's Centre, The John Radcliffe Hospital, UK.
authors.forename: P
authors.initials: P
authors.lastname: Yeh
authors.forename: K
authors.initials: K
authors.lastname: Emary
authors.forename: L
authors.initials: L
authors.lastname: Impey
mesh_terms: D000138:Acidosis / Q000097:blood / Q000150:complications* / Q000175:diagnosis; D001034:Apgar Score; D001784:Blood Gas Analysis; D001927:Brain Diseases / Q000097:blood / Q000209:etiology* / Q000401:mortality; D005312:Fetal Blood / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000097:blood / Q000150:complications; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D010343:Patient Admission / Q000706:statistics & numerical data; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D012640:Seizures / Q000097:blood / Q000209:etiology / Q000401:mortality; D014469:Umbilical Arteries