Vaginal Birth After Caesarean (VBAC)
Risks of VBAC and Caesarean Deliveries
Whether you deliver vaginally or by caesarean section, you are unlikely to have serious complications. Overall, a routine vaginal delivery is less risky than a routine caesarean, which is a major surgery. However, researchers have found that pregnant women who have a caesarean scar on the uterus have a slight risk of the scar breaking open during labour. This is called uterine rupture.1
Although rare, uterine rupture can be life-threatening for both mother and baby. Therefore, women with risk factors for uterine rupture should not attempt a vaginal birth after caesarean (VBAC).1
Risks of VBAC
The risks of VBAC include:
- An unsuccessful trial of labour that ends with a caesarean delivery (most common complication). Up to 40% of women who attempt VBAC develop a problem that requires a caesarean delivery.1 Stalled labour (called dystocia) or fetal distress are common examples of problems that require a caesarean. A caesarean after a trial of labour increases the risk of infection for both the mother and baby.1
- A slight separation of an existing caesarean scar (called dehiscence). This usually causes no problems and in some cases is not even detected. The separation usually heals on its own.
- A slight risk of uterine rupture, which can be life-threatening for the mother and the baby.7 A uterine rupture is very rare yet very serious. If the rupture cannot be repaired quickly, removal of the uterus (hysterectomy) may be necessary to prevent severe blood loss.
The possibility of uterine rupture is influenced by the:
- Type of incision used for the previous caesarean. Scarring above the thinner, lower uterus is more likely to rupture. A low, side-to-side (transverse) incision is least likely to rupture. About 5 out of every 1,000 women (0.5%) with one low, transverse incision scar have a uterine rupture during labour when the labour starts on its own without medicine.3 It is likely that these women have other risk factors that raise their chances of having this complication.
- Number of surgical uterine scars a woman has, especially if the cervix is not softened and opening (dilating). The risk of rupture increases with each additional caesarean scar. One study has shown that while a uterine rupture occurs in up to 8 out of 1,000 women with one scar, up to 37 out of 1,000 women with two scars develop a rupture.8
- Use of medicine to start (induce) labour. Among women who are otherwise good candidates for VBAC, the greatest risk factor for rupture is the use of misoprostol (Cytotec) to start (induce) or strengthen labour.3, 1 Aiding a slow labour (augmentation) with careful use of oxytocin (Pitocin) has rarely been linked to uterine rupture.9
Risks of any caesarean
The risks of any caesarean delivery include:
- Infection, which may develop in the incision.
- Blood clots (a risk with any surgery). This is rare but can be dangerous.
- Fetal injury during the delivery. The injury usually is not serious.
- Breathing problems (respiratory distress syndrome) for the baby after birth if the due date has been miscalculated and a caesarean is done before the fetus's lungs are fully developed.
To lower your risk of serious complications, arrange to deliver in a hospital that has the staff and facilities to handle an emergency caesarean delivery. A doctor must be immediately available to perform an emergency caesarean if one is needed.
Future risks. With each surgery on the uterus, more scar tissue forms. If you are planning on a pregnancy after this one, scarring is an important factor to think about. After you have two scars, each additional scar in the uterus raises the risk of placenta problems in a later pregnancy, such as placenta previa or placenta accreta. These problems raise not only the risks for a fetus but also your risk of needing a hysterectomy to stop bleeding.10
For more information about caesarean risks, see the topic Caesarean Section.
Risks of a caesarean versus a successful trial of labour
Compared with having an elective repeat caesarean, having a successful trial of labour reduces a woman's small chance of needing a blood transfusion or emergency hysterectomy (removal of the uterus) as a result of a complicated birth.7
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| Author: | Kathe Gallagher, MSW Carrie Henley | Last Updated: June 18, 2007 |
| Medical Review: | Joy Melnikow, MD, MPH - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology | |
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