VBAC versus Repeat Cesarean Delivery
There are few more contested topics in Obstetrics. Watching different strategies emerge in the management of women with prior Cesarean deliveries has been much like watching a pendulum swing over the last couple decades.
The adage “once a Cesarean, always a Cesarean” has been popular, and for some physicians repeat C sections are their preferred method of practice. However, with escalating rates of Cesarean deliveries (currently about 30% of all deliveries), and the known complications of multiple Cesarean deliveries, physicians have attempted to target a favorable group of women who are suitable candidates for Vaginal Birth After Cesarean (VBAC).
What are the risks of having a uterine scar? The most feared risk is uterine rupture. Uterine rupture occurs when there is scar separation. The immediate effects are maternal hemorrhage which can be life-threatening. The bleeding soon causes fetal distress, and if the fetus is not quickly delivered a stillbirth may occur. Most often uterine ruptures occur during the labor process. It occurs much more frequently in women who have had a “classical” Cesarean section, when there is a vertical uterine incision (NOT skin incision). A classical incision on the uterus goes through the deepest muscle, therefore making a weaker spot in the uterus. These can rupture before labor much more commonly than low transverse incisions. The rate of rupture of a classical incision is about 10%. The most common type of incision on the uterus is a “low transverse” incision, or smiley face incision in the lower part of the uterus (again, NOT on the skin but the uterus). This type of incision ruptures far less frequently, about 0.7% or 7 in 1000 pregnancies attempting labor.
However, there are very common, everyday benefits to a vaginal delivery, for both this pregnancy and future pregnancies. It is well-known that the recovery time after a vaginal delivery is much shorter for a new mom. There are also lower rates of postpartum pain, blood transfusion requirements, and infection rates. In addition, babies bord after a vaginal delivery have fewer respiratory problems in the nursery. In addition, prior Cesarean sections can cause other major future pregnancy complications like previa, placenta accreta, and increasing rates of uterine rupture.
The risk of a repeat C section should also be considered. The risks of a repeat C section are common: hemorrhage, blood transfusion, scar formation, wound and uterine infection, complications with future surgeries.
With these risks and benefits in mind, the challenge then becomes selecting the appropriate candidate to attempt a trial of labor after Cesarean delivery. In general, here are some recommendations for selecting an appropriate candidate for trial of labor:
-- Only one prior low transverse uterine incision.
-- A non-repetitive reason for first Cesarean (for instance: breech, twins, placenta previa etc).
-- Both an Ob/Gyn and Anesthesiologist in the hospital and immediately available for surgical intervention should a rupture occur.
-- No other relative contraindications to labor (such as breech, previa).
-- There has been a reasonable prepregnancy interval (of at least 6-9 months if not 1 year).
Other women may be considered in certain circumstances to undergo a trial of labor. Studies show that when a woman has two prior Cesarean deliveries, her success rate is acceptable to undergo a trial of labor if she also has a vaginal delivery. Women with a very large fetus have higher failure rates with trial of labor, however they may be considered in certain situations. Women who are unsure which type of scan they have on their uterus can be considered, especially when their physician evaluates their reasons for having a Cesarean section. Little is known with certainty about VBAC in a twin gestation, as most physicians prefer to simply do a repeat C section.
In appropriately selected women who undergo a trial of labor, the success rate for VBAC is about 70-75%. Therefore, if you are interested in trying to have a vaginal birth after a Cesarean section, talk to your doctor. If you have questions or would like more specific information, email Ask An OB with the link below.
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