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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Post-term Pregnancy and Induction of Labor
Sponsored by The Indian Health Service Clinical Support Center
6 Timing of Induction
Newer evidence exists that lends support to a policy of inducing labor earlier, at 41 weeks (287 days of gestation). As a result of the inability to make evidence-based recommendations about antenatal testing, as well as the epidemiologic data expressing stillbirth rates as a function of ongoing pregnancies (impending stillbirths divided by the total number of undelivered fetuses, not total births), data has accumulated favoring earlier induction of post-term patients.
Crowley in the 2002 Cochrane Review
summarizes 19 studies comparing routine induction at 41 weeks to expectant management with selective induction. The two largest of these trials are the Canadian multicenter study by Hannah et al
(n=3407) and the NICHD trial (n=440). The most striking result was in the variable of most interest, perinatal death, which demonstrated that routine induction at or after 41 weeks significantly reduced perinatal mortality compared to expectant management (odds ratio 0.20, 95% CI 0.06-0.70).
Few obstetric interventions that we carry out have this dramatic an effect!
Contrary to expectations that the elective induction of labor would result in an increase in the cesarean rate, a lower rate of cesarean delivery was actually found in the Canadian study. The availability and routine use of more effective prostaglandin preparations for cervical ripening and induction resulted in fewer failed inductions. Likewise, the lower incidence of fetal intolerance of labor in these less post-mature fetuses, probably also contributed to this finding of fewer cesarean deliveries.
Only one trial measured cost. Goeree R et al found that routine induction was less expensive than serial monitoring. It seems prudent to discuss these data with women who reach 41 weeks gestation with the good dating criteria discussed above.
Patients should be informed about:
- lack of evidence to support the effectiveness of any particular method of antenatal surveillance
- up to 500 inductions might be necessary to prevent one perinatal death
- there is no evidence that induction will change their likelihood of having a cesarean birth.
If the patient opts for induction, then this should best be accomplished by 294 days gestation (42 weeks 0 days). Induction may require prostaglandin ripening of the cervix if it is unfavorable, and may or may not be possible in their home community. The question of cervical ripening at a level I facility should be determined locally and the institution’s clinical guidelines.
