Uterine Rupture During VBAC Trial Of Labor: Risk Factors and Fetal Response
Journal of Midwifery & Women's Health
2003 Nancy O'Brien-Abel, RNC, MN

Abstract: For the woman with a prior uterine scar, neither repeat elective cesarean birth nor vaginal birth after cesarean birth (VBAC) trial of labor (TOL) is risk-free

Informative Excerpts for "Informed Consent" Relative to Trial of Labor /VBAC Decision Making
When VBAC-TOL is successful, it is associated with less morbidity than repeat cesarean birth. However, when VBAC-TOL fails due to uterine rupture, severe consequences often ensue.

(R)enewed controversy about the relative safety of VBAC-TOL has resulted in a rapid decline in the number of women who experience VBAC, falling from 28.3 per 100 women in 1996 to 16.4 per 100 in 2001, a 42% decrease.

Neither repeat cesarean birth nor TOL after cesarean is risk-free for women with a prior uterine scar. When VBAC-TOL is successful, it is associated with less morbidity than repeat cesarean birth.[2-5, 9, 13]
However, when VBAC-TOL results in uterine rupture, neonatal death or permanent neonatal injury can occur even in facilities with immediate access to cesarean birth.

A woman and her health care provider must evaluate the following: 1) risk of complications associated with VBAC-TOL versus repeat elective cesarean birth, 2) capabilities of the birth facility, 3) personal choice, and 4) the probable success rate of VBAC-TOL.

Recent research has better defined factors that influence probable success of VBAC.
Characteristics in a woman's obstetric history (type of uterine scar, single-layer versus double-layer uterine closure, number of prior cesarean births, number of prior vaginal births, interdelivery interval, maternal age, maternal fever following cesarean), in addition to factors related to current labor management (induction or augmentation with prostaglandins and/or oxytocin), have been found to significantly influence uterine rupture rates during VBAC-TOL.
.... the authors concluded that women with a prior low vertical uterine incision are not at increased risk for uterine rupture during TOL compared with women who had a prior low transverse uterine incision.
In a recent, larger, observational cohort analysis, Bujold et al.[35] identified a nearly four-fold increased incidence of uterine rupture during VBAC-TOL in women who had a single-layer closure of the previous lower uterine segment incision compared to women who had a previous double-layer uterine closure
At the time of the initial cesarean, single-layer closure was used in 489 women and double-layer closure in 1491 women. Uterine rupture occurred in 15 (3.1%) of the women with previous single-layer closure and in 8 (0.5%) of the women with a previous double-layer closure (P < .001). On the basis of these findings, the authors recommended that surgeons consider using a double-layer closure technique for women who may subsequently experience a TOL.

Uterine rupture occurred in 1.7% of the women with two or more previous cesareans compared with a uterine rupture incidence of 0.6% in those with only one prior cesarean birth (OR: 3.06; 95% CI: 1.95-4.79; P < .001). However, this retrospective analysis did not control for other aspects of the women's obstetric history or labor management.
Uterine rupture occurred in 1% (3/302) of the women with two or more prior cesareans compared to 0.5% (5/1,110) in the women who had one prior scar on the uterus. More recently, Caughey et al.[37] conducted a retrospective analysis of 3871 women who underwent a VBAC-TOL. The rate of uterine rupture was 3.7% among 134 women in the two-scars group compared to 0.8% in the 3,757 women with one previous uterine scar
After controlling for maternal age, epidural analgesia, oxytocin induction, oxytocin augmentation, use of prostaglandin E2 gel, birth weight, gestational age, type of prior hysterotomy, year of TOL, and prior vaginal delivery, women with two prior cesarean scars were still 4.8 times more likely to experience uterine rupture during VBAC-TOL than women with one prior uterine scar (OR: 4.8; 95% CI: 1.8-13.2).

In summary, women with two or more prior uterine scars have a significantly increased risk of uterine rupture during VBAC-TOL compared to women with only one prior uterine incision.
Although the number of previous cesarean births appears to increase a woman's risk for uterine rupture during a VBAC-TOL, prior vaginal birth appears to be somewhat protective.

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