Mifepristone versus Foley balloon catheter for outpatient cervical ripening at term: A non-inferiority randomised controlled trial

Objective: To evaluate whether the success rate of oral mifepristone was not inferior to that of Foley balloon catheter for outpatient cervical ripening of term pregnancies, and whether there were differences in side effects for mothers and newborns.

Design: Open-label, non-inferiority randomised controlled trial.

Setting: A tertiary care European university hospital in an urban setting.

Population or sample: A total of 101 women with a Bishop's score < 6 and with an indication for outpatient cervical ripening at term.

Methods: Participants were randomly allocated to receive either mifepristone 200 mg per os, or an intracervical Foley catheter balloon.

Main outcomes measures: Women going into labour in the first 24 h after the intervention or with a favourable Bishop's score (≥6) at the first re-evaluation, conducted 18-24 h after the intervention. We hypothesized that the incidence of the main outcome in the mifepristone group would be similar to that of the Foley balloon catheter group, within a margin of 10 %.

Results: Onset of labour or favourable Bishop's score were achieved in 33.3 % of women receiving mifepristone and 30.2 % of those receiving the Foley balloon catheter (risk difference 0.03, 95 % confidence intervals -0.15 to 0.21). This confidence interval indicates that mifepristone can be 21 % superior but can also be 15 % inferior to the Foley catheter balloon, therefore not meeting our non-inferiority target of less than 10 %.

Conclusions: Similar rates of onset of labour or favourable Bishop's score were achieved with mifepristone and Foley balloon catheter in outpatient cervical ripening at term, but mifepristone could not be shown to be noninferior.