Vaginal birth after cesarean (VBAC): Clinical sciences

.Vaginal birth after cesarean, also known as VBAC, refers to a successful vaginal delivery in a patient with a prior C-section. While many patients may choose to undergo a trial of labor after cesarean, also known as TOLAC, to avoid the risks of major abdominal surgery, others may elect for a repeat C-section due to the increased operative risks with an intrapartum C-section compared to a planned one.

Ultimately the decision must be individualized but it is important to know the risks, benefits, and contraindications, so you can provide your patient with the best information to make their decision.

The first step when a patient presents desiring a TOLAC is to perform a focused history and physical examination, …

with particular attention to their obstetric history. This means obtaining the past operative note to know what kind of C-section they had. The most common type of C-section is one where a low transverse incision is made in the lower uterine segment of the uterus to deliver the infant.

However, sometimes a classical C-section is performed where a vertical incision is made in the contractile portion of the uterus. This is important because TOLAC is not recommended for a patient with a prior classical C-section, due to a higher risk of the uterus rupturing during labor.

Patients with a history of an extreme preterm delivery, a history of significantly large fibroids, or a history of a difficult extraction of the infant may have had a classical C-section.

Here are a couple of clinical pearls! You can’t determine the type of uterine scar by looking at the direction of the skin incision. Sometimes vertical skin incisions are made while the uterine incision is low transverse; alternatively, a patient may have a low transverse skin incision but their uterine incision is vertical, meaning it’s classical. Additionally, some types of uterine surgery should be treated as if the patient had a classical C-section. This happens when incisions are made into the contractile portion of the uterus, such as when removing large intramural leiomyomas during a myomectomy.

Okay, back to your patient. You’ll also want to know the number of prior C-sections. The risk of uterine rupture increases with each previous C-section. Generally, TOLAC is considered safe with one or two prior C-sections, though this may vary by provider comfort.

It’s also helpful to know the indication for the prior C-section. Patients who have previously had an arrest of dilation or descent are less likely to have a successful VBAC. Alternatively, a patient who had a C-section for breech or for non-reassuring fetal assessment could be more likely to have a successful VBAC, simply because they haven’t been able to truly labor before.

Also ask your patient about prior vaginal births, because a prior vaginal birth, either before or after their C-section, will also increase the odds of successful VBAC.

Be sure to find out when the C-section was performed, as an interval of at least 18 months is ideal to allow the uterine scar to fully heal.

Other things worth considering are age, height, prepregnancy weight, and history of hypertension, as these impact the chances of successful VBAC. Remember, these historical factors can only help provide an estimate of the chances of success if your patient decides to attempt a VBAC.

Ultimately each patient has to make their own decision, but providing an estimate of their odds for a successful trial of labor will help to prevent the complications associated with an intrapartum C-section.

Now, if your patient has a contraindication to TOLAC, such as a prior classical C-section, more than two prior C-sections, or any contraindication to labor in general, perform a repeat C-section when delivery is indicated.

On the flip side, if there are no contraindications to TOLAC, there are many things to discuss when planning delivery.

You need to review the risks and benefits of both TOLAC and planned repeat C-section with your patient. A planned repeat C-section carries all the risks that come with a major abdominal surgery.