B29. Vaginal delivery after prior uterine surgery
Vaginal birth after caesarean delivery (VBAC) refers to delivering vaginally after having previously delivered by C-section. The decision of whether to attempt vaginal labour next pregnancy or have a planned repeat caesarean delivery (PRCD) must be made together with the patient.
VBAC is considered successful if the foetus is successfully birthed vaginally, no emergency C-section required. The success rate of VBAC is 70% after one previous C-section, and 50% after two or more. However, several factors increase the likelihood of a successful VBAC, most notably having had a previous vaginal birth (previous VBAC or vaginal birth before C-section).
Risks
There are always risks associated with C-section, but after a previous C-section, the risk for certain complications during vaginal birth increases as well, most notably uterine rupture. These risks must be weighed against each other to be able to recommend the safest approach for the patient.
Emergency C-sections are riskier than planned ones. If VBAC is attempted but a situation occurs where emergency C-section is necessary, the risk is higher than if a C-section was planned. If VBAC is attempted, the institution should be prepared to perform C-section in case a situation that is an immediate threat to the woman or foetus.
The most important risks are:
- Maternal death
- Risk of maternal death is higher for PRCD (3x higher)
- Absolute risk still low (0,013% with PRCD)
- Uterine rupture
- Risk of uterine rupture is higher for VBAC (20x higher)
- Absolute risk still low (0,47% with VBAC)
- Perinatal and neonatal mortality
- Risk of mortality is higher for VBAC (2x higher)
- Absolute risk still low (0,12% for VBAC)
Other advantages and disadvantages
In addition to the risks themselves, there are other factors which may influence the patient’s preference of VBAC or PRCD. Advantages of VBAC:
- Avoiding C-section decreases risk of placentation disorders (praevia, accreta), which could be harmful for future pregnancies
- Avoiding C-section means a quicker return to normal life (shorter hospital stay)
- Patient gets to experience vaginal birth
- Partner can be involved in the birth
- Fewer post-op complications
Advantages of PRCD:
- Easier to schedule
- Sterilisation can be performed simultaneously
- Avoidance of vaginal labour-related pain
Contraindications to VBAC
- Any regular contraindications to vaginal birth (placenta praevia, etc.)
- Previous uterine rupture
- Previous C-section with a classic longitudinal incision
- (Nowadays the low transverse incision is the standard)
- Previous uterine surgery (for leiomyoma, etc.)
Recommendations
Generally, it’s recommended that it’s safe for women with one previous C-section to attempt VBAC. If she has underwent two or more C-sections, VBAC can still be safe if there are factors present which increase the likelihood of successful VBAC, like previous vaginal birth.
Online calculators[1] exist to estimate the probability of successful vaginal delivery based on the maternal characteristics and obstetric history. These calculators do not calculate the probability of complications.