With interest we read the article by Tuuli et al (2013), who compared, in a retrospective cohort study, induction of labor with vaginal misoprostol or a Foley catheter. The authors found that induction of labor with a Foley catheter in comparison with vaginal misoprostol was associated with initially more rapid cervical dilation, but transition to active labor occurs later.

However, in our opinion there are several methodological issues that raise concern. First, the Foley catheter group included 114 patients compared with 503 in the misoprostol group; second, only women who fulfilled the first stage of labor were included. This contrast in number of patients and in the selection of women may have introduced bias. The differences in patient characteristics between both groups, such as cervical dilatation, indication for induction, and prior cesarean section in the Foley catheter group but not in the misoprostol group, hamper comparison. Propensity score matching would have been preferred over the multivariable approach the authors chose.

Of more important concern, however, is the choice for time to delivery as the main and only reported outcome. In our opinion, the effectiveness of induction (ie, vaginal birth after induction of labor) and more important safety for mother and child are far more essential measures when comparing methods for induction of labor. A safe delivery is in our opinion much more valuable than a fast one. We respectfully disagree with the Cochrane collaboration, World Health Organization, and National Institute for Health and Care Excellence, who all establish that birth within 24 hours of the start of induction is the “clinically most relevant measure of effectiveness for trials of methods of labor induction.” We would be interested to see the measures of safety and effectiveness after misoprostol and Foley induction reported by Tuuli et al, preferably after propensity score matching.