We thank Dr Eikelder and her colleagues for their interest in our study comparing progress of labor in women induced with vaginal misoprostol or the Foley catheter. They contend there is selection bias because we have an unequal number of subjects in the 2 groups; only women who completed the first stage were included and women with prior cesarean were only in the Foley catheter group. They propose propensity score matching rather than the multivariable approach we used and are concerned about our choice of time to delivery (efficiency), rather than effectiveness and safety, as the primary outcome.

Although we applaud their continued interest in our work, we believe their concerns lack a solid foundation. First, misoprostol and the Foley catheter have both been shown to be safe and effective for cervical ripening and labor induction. Therefore, our stated objective was not to duplicate that work but to describe and compare the progress of labor in women induced with these methods. In addition, contrary to the authors’ belief, efficiency of labor induction is of value to women and their care providers, especially when making a choice between 2 methods that are both safe and effective.

Second, differences in the numbers of subjects in the 2 groups per se do not constitute selection bias. Limiting the analysis to women who completed the first stage of labor was necessary to facilitate the use of contemporary analytical tools for labor data, and because this applied to both groups, any bias would be nondifferential.

Third, we sought to provide data for clinicians on labor progress, and specifically the timing of the onset of active labor, in women induced with the 2 methods as selected based on routine clinical judgment. Therefore, the use of propensity score matching would not be appropriate.

Finally, the concern that women undergoing a trial of labor after cesarean were only in the Foley catheter group might have an impact on the results is not supported by the existing data. Prior work clearly demonstrated no differences in the expected labor progress in women with prior cesarean delivery.

In conclusion, we believe our study makes an important contribution to existing literature by demonstrating that the expected labor curves for women induced with misoprostol or Foley catheter are different, a fact that should be considered in diagnosing labor arrest in women selected to these methods. Because women were selected for the different methods based on routine clinical judgment, this comparison of efficiency is clinically relevant.