Population adjustment of the definition of the vaginal birth after cesarean rate

OBJECTIVE: The vaginal birth after cesarean delivery rate is calculated wit h a denominator equal to the number of all women who give birth after a pre vious cesarean delivery, including those who are not candidates for a trial of labor. We evaluated the impact of adjustment for noncandidates for a tr ial of labor on vaginal birth after cesarean delivery rates. STUDY DESIGN: All women with a previous cesarean delivery who were delivere d during 1998 were classified as either candidates or noncandidates for a t rial of labor. An adjusted vaginal birth after cesarean delivery rate was c alculated by eliminating noncandidates for a trial of labor from the denomi nator. The percentage of noncandidates for a trial of labor, the vaginal bi rth after cesarean delivery rate, and the adjusted vaginal birth after cesa rean delivery rate were compared among 3 clinical services. RESULTS: The maternal-fetal medicine service had a significantly higher per centage of noncandidates for a trial of labor than did either the low-risk resident clinic or the low-risk private service, The maternal-fetal medicin e service had a significantly lower vaginal birth after cesarean delivery r ate than did the private service, but this difference was no longer present after application of an adjusted vaginal birth after cesarean delivery def inition. CONCLUSION: For accurate comparison of vaginal birth after cesarean deliver y rates among providers it is essential to account for patient risk status in the vaginal birth after cesarean delivery definition through the elimina tion of noncandidates for a trial of labor.