Spurt release of oxytocin during surgical induction of labor in women.

Oxytocin levels were measured in closely spaced samples of maternal blood from 10 women who underwent amniotomy for induction of labor. The procedure was associated with a spurt release of oxytocin, the highest frequency being found during sweeping and rupture of the membranes. It was concluded that the main stimulus to this release was vaginal distention (Ferguson's reflex) and that the same mechanism probably accounts for the increase in maternal oxytocin during the expulsive phase of labor.