Vaginal Birth after Cesarean Section (VBAC)
Many people who have had a cesarean section in a prior pregnancy consider having a vaginal birth in a subsequent pregnancy. There have been numerous studies over the years that have looked at this situation, and the most recent data will be summarized here.
Overall likelihood of success of VBAC: about 70%.
This may seem like a very high success rate, but the number may be skewed too high because not every patient tries to have a VBAC (many choose to have an elective repeat cesarean section). Those that do not try to “VBAC” may be at higher risk for a failed VBAC because of their personal experience the first time around (and thus leaving a subset of patients that is more likely to succeed).
Risk of uterine rupture: between ½ and 1 percent.
This number has been surprisingly constant in multiple studies and, recently, was confirmed in two large studies. Fortunately, the risk of a catastrophic uterine rupture is low (see below). Most cases of uterine rupture can be diagnosed in labor, as a non-reassuring fetal heart rate tracing, and a cesarean section can be performed without injury to the mother or baby.
Risk of catastrophic uterine rupture: approximately 1 out of 1000.
Unfortunately, there can be rare cases of uterine rupture where the oxygen supply to the fetus is interrupted. This can happen suddenly, without warning. This could lead to cases of brain damage (hypoxic encephalopathy) and/or cerebral palsy. To date, very few risk factors for uterine rupture are known, but a prior “classical” uterine incision (a vertical uterine incision) and a prior uterine rupture are two such known risk factors. Patients with such histories should be delivered by repeat cesarean section.
Risk of uterine rupture with two or more previous cesarean sections: about 2-fold greater than with 1 prior cesarean delivery
Is induction of labor possible with a previous c-section? The recent literature is clear that induction of labor is possible with, perhaps, only small increases in uterine rupture rates.
The benefits of VBAC are:
• a potentially faster postpartum recovery and quicker return to pre-delivery activities
• a shorter hospital stay
• on average, less blood loss
The disadvantages of VBAC are:
• not knowing when labor will occur
• rupture of the uterus can occur (see above) necessitating an emergency delivery
The benefits of elective repeat cesarean section are:
• one can schedule their delivery to accommodate work schedules and allow for placement of their older child or children
• decreased risk of uterine rupture
The disadvantages of elective repeat cesarean section are:
• more painful postpartum course with slower return to pre-delivery activities
• increased blood loss
• risk, albeit low, of damage to nearby organs (bladder, bowel, ureters, etc.)
• higher risk of post-operative infections (bladder, uterine, wound)
• a higher risk in a future pregnancy of a condition called placenta accreta, a condition that can lead to a hysterectomy at the time of cesarean section (caused by an abnormal attachment of the placenta)
Who is a candidate for VBAC? Anyone with 1 or 2 previous cesarean sections with a prior “low transverse” scar (on the uterus) who understands that there is a low risk of uterine rupture with the even less likely possibility of a compromised child (e.g., brain damage or cerebral palsy) because of a catastrophic rupture. A patient that has had a prior cesarean delivery and who also had a prior vaginal delivery is even more likely to succeed with a VBAC.
Who should be counseled to schedule a repeat cesarean section? A patient who previously needed a c-section for dystocia (a baby that “didn’t fit”) who is now past her due date with a suspected larger child and an unfavorable exam. Also, any patient who is not willing to accept the risk, though small, of uterine rupture should also be encouraged to have a repeat cesarean section.
I, __________________________ , have read the VBAC information sheet provided to me by my physician and I:
• would like to have a trial of labor (undergo a ‘VBAC’).
• would like to schedule a repeat cesarean section.
Please note that any decision you make now can be changed at any time (you can change your mind!).
Please consult other links on my website for more information on this subject.
Peter T. Simonson, MD