• 1 in 625 with a planned repeat cesarean,
  
• 1 in 192 with starting labor on their own,
  
• 1 in 130 with an induction of labor but without using prostaglandin to soften the cervix first,
  
• 1 in 41 with labor inductions that included prostaglandin.

While potentially serious, the scar giving way, though, is not the crucial issue in determining the safety of VBAC, but rather what happens to the mother and baby as a result. Even when uterine rupture occurred, only one-third of the women experienced a surgical complication during the emergency cesarean that would usually follow. As for irremediable harm, for a woman beginning labor spontaneously, the chance of ending up with a hysterectomy was 1 in 5,000 and of losing the baby was 1 in 3,300. For women being induced without use of prostaglandin, the odds went up only slightly, but when labor induction included prostaglandin, they soared to 1 in 900 for hysterectomy and 1 in 770 for infant death.

In point of fact, this study had nothing to say about the merits of planned cesarean versus VBAC because it only considered uterine rupture. And while VBAC women have a slightly greater risk of this, cesarean section introduces a host of other complications that occur much less often with vaginal birth. To evaluate which is better, you have to compare outcomes between women having a planned repeat cesarean with women planning VBACs. Those studies exist. Among thirty studies comprising 56,300 VBACs, the rate of stillbirths and newborn deaths attributable to uterine rupture was 1 in 3,300, the same as in the Washington State women beginning labor spontaneously. Those odds did not differ significantly from the perinatal mortality rate in 29,900 women having planned cesareans. In other words, VBAC was no riskier for babies than planned cesarean.