Effect of abolition of fetal movement on fetal intravascular PO2 and incidence of tonic myometrial contractures in the pregnant ewe at 114 to 134 days' gestation.

The possibility that fetal movements play a role in the initiation of the bursts of tonic myometrial activity (contractures) that occur throughout the second half of pregnancy in the sheep has been examined by the administration of the curare derivative pancuronium to abolish fetal movement. The duration and frequency of the electromyographic bursts associated with contractures, as well as the increase in intrauterine pressure generated by the contractures, were unchanged. However, within 1 hour of the abolition of fetal movement, fetal jugular venous PO2 was significantly elevated and remained elevated for at least 6 hours. This observation is in keeping with the view that fetal skeletal muscle movement consumes significant amounts of oxygen.