Changes in arterial blood gases following cardiac asystole during fetal life.

A case of suspected fetal cardiac asystole with normal umbilical cord blood gas values is reported. Possible explanations of this apparent discrepancy were examined by measuring sequential changes in fetal arterial acid-base and blood gas values after induced cardiac asystole in chronically instrumented fetal lambs at 132-141 days' gestation. Arterial pH values did not decrease from baseline for at least ten minutes. Elevation of pCO2 values were observed at 30 minutes. Arterial pO2 and HCO3 values remained unchanged for at least 30 minutes. Therefore, we conclude that sudden fetal cardiac asystole occurring within ten minutes of delivery may be one reason why umbilical cord acid-base and blood gas values do not correlate with Apgar scores.