Correlation of the one-minute Apgar score and umbilical cord acid-base status

The one-minute Apgar score has proven useful by ensuring rapid assessment of the neonate, but is often poorly correlated with other indicators of intrauterine well-being. Since fetal asphyxia is directly associated with neonatal acidosis, a low Apgar score in the face of normal pH and base deficit does not indicate an asphyxiated infant. In a study to ascertain the feasibility of combining umbilical artery pH with the one-minute Apgar score for neonatal assessment, umbilical artery pH and Apgar scores were obtained on 212 singleton pregnancies. When the Apgar score was less than 7, more than half (60%) of the neonates had a normal umbilical artery pH. Fifty-one percent of this group had had intubation and nasopharyngeal suctioning, procedures known to be associated with lowered Apgar scores. When reviewing the umbilical artery gas values and base deficit in those neonates with a pH less than 7.20, we found that of the eight patients with an Apgar score of 7 or greater, seven (87.5%) were classified as having metabolic acidosis, with only one having respiratory acidosis. In the neonates with Apgar scores of less than 7, approximately two thirds had blood gas values compatible with metabolic acidosis, while the others displayed respiratory acidosis. We recommend, therefore, that neonates with a one-minute Apgar score less than 7 have umbilical artery pH determinations to confirm the presence or absence of acidosis. We also recommend that when the pH is less than 7.20, a complete set of gas values be evaluated with that specimen. This information offers more precise confirmation of the diagnosis of fetal distress and neonatal asphyxia, both for treatment and more reliable follow-up data, as well as for medicolegal purposes.