Reducing the Caesarean Delivery Risk in Elective Inductions of Labour: A Decision Analysis

Abstract

Elective inductions of labor at 39 to 41 weeks' gestation, done for reasons of convenience rather than to promote mother or child health, are not uncommon in the U.S. The cesarean delivery rate might be reduced if nulliparous women at high risk of requiring surgery could be identified. Bishop scores do not accurately predict the outcome of induction, whereas fetal fibronectin (fFN) has been suggested as a possible way of detecting high-risk parturients. The authors performed a decision analysis to test three options: induction only after 41 completed weeks of pregnancy; testing nulliparous women for fFN at 39 weeks' gestation and inducing labor if the test is positive (if negative, expectant management is undertaken, awaiting spontaneous labor), and elective induction for all women at 39-41 weeks' gestation. Allowing spontaneous labor carried a vaginal delivery rate of 90%, whereas the lowest rate of 79% correlated with the elective induction strategy. When fFN testing was used to screen candidates, elective induction resulted in 83% of cases. A mother had to assume an additional 7% risk of cesarean delivery to warrant fFN screening and an additional 11% risk to have induction without screening. Utility analysis showed that if a mother desired a less than 10% risk of cesarean delivery, she should not have induction. If, however, she is willing to take a 10% to 21% chance, fFN testing is the best course. If a risk greater than 21 % is acceptable, elective induction would be the preferred option. The specificity of the fFN test could influence which option is most advantageous. Analyzing U.S. natality data for 1997, avoiding elective induction for nulliparous women could save 8752 cesarean deliveries each year and would save an estimated $38 million. The results of this decision analysis suggest that the best way of increasing vaginal delivery rates is for nulliparous women to avoid elective induction of labor. If it is decided to proceed with elective induction, fFN testing may improve the chance of avoiding cesarean section.