Fetal scalp blood pH sampling: its value in an active obstetric unit

Two hundred thirty-two patients had fetal scalp blood pH sampling performed from January 1, 1978, to September 30, 1978. Ninety-eight percent of samples were obtained for fetal heart rate (FHR) changes: 62% for variable decelerations, 10% for late and 3% for early decelerations, 10% for decreased baseline variability, and 12% for baseline rate abnormalities. Fourteen fetuses were mildly acidotic, and six were severely acidotic. All were delivered within 1 hour of the last fetal blood sample. Acidosis was significantly more frequent with late decelerations (p less than 0.05). Neonatal depression was significantly more frequent (50% incidence) only with severe fetal acidosis (p less than 0.05). Complications of fetal blood sampling occurred in 15 infants (6%), and all were minor. Based on independent review of the FHR tracings by three members of the perinatal department, it was estimated that 20 to 30 cesarean sections were avoided by determining fetal blood pH (approximately 10%).