Fetal subcutaneous scalp PO2 and abnormal heart rate during labor

Intrapartum fetal heart rate and subcutaneous scalp PO2 were continuously measured with a combined electrocardiogram-PO2 needle electrode in 34 patients. The incidence of fetal heart rate abnormalities increased significantly with decreasing subcutaneous PO2, from 0.8% of the 10-minute periods in which subcutaneous PO2 was greater than or equal to 25 mm Hg to 53% of the periods in which subcutaneous PO2 was less than 10 mm Hg.