A practical approach to umbilical artery pH and blood gas determinations.

The use of the Apgar score as a means of identifying birth asphyxia has been challenged. Routine umbilical cord blood pH has been recommended as a more objective measure of the condition of the newborn. The purposes of this study were to evaluate a simplified and selective method of umbilical artery pH blood sampling and to determine the effect of delay in sampling upon umbilical artery pH, carbon dioxide pressure (PCO2), and oxygen pressure (PO2). Umbilical arterial blood of 25 patients was sampled from clamped umbilical cord segments every 15 minutes for 1 hour after delivery. The clamped umbilical cord segments were left at room temperature with no special care given. The blood samples were collected in non-heparinized and non-iced plastic syringes and processed promptly after sampling. During the 60 minutes after delivery, there were no statistically significant changes in pH, PCO2, or PO2 of umbilical arterial blood. Our results indicate that umbilical arterial blood may be obtained simply and reliably from clamped umbilical cord segments for pH and gas determinations for up to an hour after delivery.