Effect of segmental extradural analgesia on placental blood flow during normal labour.

Placental blood flow was measured during the first stage of normal labour using a xenon-133 clearance technique before and after segmental extradural analgesia. Analgesia was produced with 0.5% plain bupivacaine in eight patients and with 0.5% bupivacaine--adrenaline in 10 patients. Segmental extradural analgesia with a small dose (20 mg) of bupivacaine did not change placental blood flow significantly. The addition of adrenaline 20 microgram produced no effect.