Questioning the Practice of Routine Umbilical Cord Blood pH Sampling at Delivery

Abstract

The objective of this study was to review the results of the practice of routine cord blood pH determination in order to ascertain its value and cost-effectiveness in patient care. Retrospective study of all deliveries in two hospitals for 1 year was carried out, correlating pH with outcome. Two teaching hospital obstetric services with somewhat different patient populations but similar practices were selected for the study. The participants comprised all 3,183 delivered patients on whom samples were obtained and 398 without sampling. Babies were followed up by chart review through the time of transfer or discharge.

Cord arterial pH values averaged 7.31 +/− 0.08 S.D., with 103 (3.2%) showing values > −2 S.D. (<7.16); only 19.4% of these had low Apgar scores (<7) at 5 minutes. Of all babies delivered, 61 (1.9%) had low Apgar scores, but only one-third had low pH values. Both the low Apgar and low pH groups had increased frequencies of prolonged hospital stays and of anomalies. Those with low pH but without low Apgar scores generally behaved as normal newborns and were discharged at expected times. Low pH was associated with normal Apgars in 2.6% of cases.

True asphyxial events and findings of early neurologic abnormality were very rare. Correlations between low pH or Apgar scores and outcomes were uncommon. The practice cost consumers over $100,000. The data raise serious questions as to the utility of routine, nonselective sampling of vigorous newborns.

Key Words:

• Asphyxia
• Cerebral palsy
• Labor