Association between Number of Previous C/S or TOLAC/VBAC and Risk of Uterine Rupture
In order to understand the overall risks of rupture, it is important to consider a number of variables regarding the risk of rupture in the following cases:
  • ERCS, (all gestational ages) not in labor (1:3900)
    • at term, 37 weeks+ (1:4400)
  • ERCS or TOLAC (all gestational ages) in labor (1:300 to 1:100)
    • at term, 37 weeks+ (1:125)
  • TOLAC, augmentation of labor using oxytocin (1:250 to 1:100)
  • TOLAC, induction of labor using oxytocin (1:65 to 1:50)
    • at term, 37-40 weeks (1:65)
    • greater than 40 weeks (1:30)
    • Using Prostaglandins (1:20)
  • Previous Vaginal Delivery and/or Successful TOLAC/VBAC (1:200)
    • Induction with oxytocin (1:100 to 1:50)
  • Unscarred uterus in labor (1:30,000 to 1:10,000)
The general consensus is that the risk of uterine rupture increases as the number of previous C/S increases; however, the overall risk appears to be within the absolute risk range of a single C/S.

Studies suggest that the risk of uterine rupture is between 0.47%- 1% for previous C/S x1. For women who have had multiple C/S: Landon et al. (2006) suggest the risk of rupture rises to 0.9%. Fitzpatrick et al. (2012) also found a slight increase in risk for women how had had 2 or more previous C/S. However Cahill et al. (2010) found that:

"Women with three or more prior caesareans who attempt VBAC have similar rates of success and risk for maternal morbidity as those with one prior caesarean, and as those delivered by elective repeat caesarean."
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