From the Guidelines
Attempting a vaginal birth after a classical cesarean section is not recommended due to the high risk of uterine rupture, which can be as high as 4-9%. This risk is significantly higher compared to the risk associated with low transverse cesarean sections, which is around 0.5-1% 1. A classical C-section involves a vertical incision in the upper part of the uterus, creating a weaker scar that is more prone to separating during labor contractions.
Key Considerations
- Uterine rupture is a life-threatening emergency that can cause severe hemorrhage, fetal distress, and even death of the mother or baby.
- The method used for inducing labor affects the risk of uterine rupture, and certain methods like misoprostol (Cytotec) should not be used for cervical preparation or induction of labor in women who have had a previous cesarean delivery 1.
- Women with a history of classical C-section should be scheduled for a repeat cesarean delivery before labor begins, typically around 36-37 weeks of pregnancy to avoid spontaneous labor.
Clinical Implications
- The American College of Obstetricians and Gynecologists considers a prior classical cesarean an absolute contraindication to trial of labor.
- It's crucial for women who have had a classical C-section to inform their healthcare provider early in pregnancy to plan appropriate delivery timing and ensure proper monitoring throughout their pregnancy.
- Given the high risk of uterine rupture and its potential consequences, it is essential to prioritize a scheduled repeat cesarean delivery over attempting a vaginal birth after a classical cesarean section.
From the Research
Risk of Uterine Rupture after Classical C-Section
The risk of uterine rupture is a significant concern for women who attempt to labor after a classical C-section. According to the available evidence:
- Women with a previous classical uterine incision should not undergo a trial of labor and should be delivered once fetal lung maturity is documented 2.
- The risk of uterine rupture is higher in women who attempt a vaginal birth after cesarean (VBAC) compared to those who undergo an elective repeat cesarean section 3.
- The overall frequency of complete uterine rupture in women who attempt VBAC is approximately 0.63% 4.
Factors Influencing Uterine Rupture Risk
Several factors can influence the risk of uterine rupture in women who attempt VBAC:
- Prior vaginal delivery is associated with a lower risk of uterine rupture (adjusted odds ratio [aOR] 0.3,95% CI 0.2-0.5) 4.
- Induction of labor is associated with a higher risk of uterine rupture (aOR 2.2,95% CI 1.4-3.4) 4.
- Labor before a primary cesarean delivery can decrease the risk of uterine rupture in a subsequent trial of labor 5.
Specific Considerations for Classical C-Section
While the available evidence does not provide a specific risk estimate for uterine rupture after a classical C-section, it is generally recommended that women with a previous classical uterine incision shouldn't attempt a trial of labor 2. This is due to the increased risk of uterine rupture associated with classical incisions.
Comparison with Other Delivery Methods
The risk of uterine rupture is significantly higher in women who attempt VBAC compared to those who undergo a planned repeat cesarean delivery (PRCD), particularly in twin gestations (OR: 9.43; CI: 3.54-25.17) 6. However, the absolute risk of uterine rupture remains low in both groups.