Postterm Pregnancy: Putting the Merits of a Policy of Induction of Labor into Perspective

Abstract

Several randomized, controlled trials compared the policies of induction of labor and expectant management for women who reach 41 weeks' gestation, and although they suggest a better outcome for mothers and infants with such a policy in place, controversy continues as to which is the better form of care. The Canadian Multicenter Postterm Pregnancy Trial (CMPPT) enrolled 3407 women, of whom 1701 were randomized to a policy of induction of labor (induced group) and 1706 were randomized to a policy of expectant management (expectant group). Secondary analyses of data from the CMPPT were undertaken to explore a number of controversial issues. We used data from the CMPPT to explore further the timing of delivery for women enrolled between 41 0/7 and 41 6/7 weeks' gestation, the potential impact of more liberal use of prostaglandins on cesarean section rates, and the relative merits of induced versus spontaneous labor in the two groups. Most women in the CMPPT (89%) were enrolled at 41 0/7 to 41 6/7 weeks' gestation, of whom 86.2 percent in the induced group and 63.6 percent in the expectant group gave birth before 42 weeks' gestation. Assuming that administration of prostaglandins would reduce the likelihood of cesarean section by 12 to 15 percent, cesarean section rates were reduced in the induction group from 21.2 percent to 20.8 to 20.9 percent, and in the expectant group from 24.5 percent 23.3 to 24.2 percent. If labor was induced as part of a policy of expectant management, the cesarean section rate was much higher (33.5%) than if labor was either spontaneous or induced as part of a policy of induction (18.5%, 22.4%). Women should be informed of the benefits and risks associated with the policies of induction of labor and expectant management, and their preferences regarding these policies should be respected.