I have four studies of truly elective repeat cesarean in which the cumulative scar rupture rate was 0.2 per 1000. I can't quite nail down the rate in your optimal-for-VBAC population, but it should be 4 per 1000 or less. Four per 1000 was the rate in the big Landon 2004 study in women with spontaneous labor onset who labored without oxytocin augmentation. In the birth center VBAC study, the rate in women with one prior cesarean who had not reached 42 weeks gestation was 2 per 1000. These women, too, would have had spontaneous onset and no augmentation. Put positively, the women you describe should have a 99.6% to 99.8% odds of an intact uterus. Moreover, in the few women who had the scar give way, except for rare cases, the only adverse outcome would be an urgent repeat cesarean. Against this, must be considered the potential harms of accumulating cesareans for the mother, baby, and future pregnancies.
Thank you for your enthusiasm about the new edition.
-- Henci
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