Objective: To determine the prevalence, magnitude, and type of fetal acidemia associated with contemporary obstetric anesthetic techniques.
Methods: Umbilical artery blood gases were obtained in 1601 singleton pregnancies delivered by elective cesarean.
Results: General anesthesia was used in 371 (23%) women, epidural in 286 (18%), combined spinal-epidural in 659 (41%), and spinal in 231 (14%). Approximately 18% of infants exposed to regional anesthetics had umbilical artery blood pH values 7.19 or less, 42 (3%) infants had pH values less than 7.10, and nine (1%) had values 6.99 or less. The incidence of fetal acidemia was greater in spinal and combined spinal-epidural procedures compared to epidural anesthetics. Fetal acidemia was predominantly respiratory in type because carbon dioxide pressure was abnormally increased when fetal acidemia was diagnosed.
Conclusions: Regional anesthesia is associated with fetal acidemia, occasionally severe, and has features of an acute respiratory type of acidemia. Fetal acidemia is less frequent with epidural anesthesia compared to subarachnoid techniques.