7 Surprising Studies on VBAMC

In 2017 ACOG released practice bulletin 184 with updated guidelines for VBAC. In the guidelines it states that "most women with one previous cesarean delivery with a low transverse incision are candidates for and should be counseled about VBAC and offered TOLAC". About VBA2C it states that "it is reasonable to consider women with two previous low transverse cesarean deliveries to be candidates for TOLAC, and to counsel them based on the combination of other factors that affect their probability of achieving a successful VBAC". However, there is no recommendation for those with more than two repeat cesareans although, they do use the term "more than one cesarean delivery" and "after two cesareans" almost interchangeably. VBAMC stand for VBAC After Multiple Cesareans. Basically it is an all inclusive term of VBA2C, VBA3C, VBA4C, etc...

So, how do you decide what the risks are for attempting VBAMC? I am so glad you asked! There have been seven studies in recent history addressing that exact thing. I am going to briefly summarize the largest seven of them here, then link to where I found them so you can dig even further, if you would like.

The risk of rupture for those with more that two cesareans is widely unknown. VBAC's of this nature have definitely happened and we hear stories of them here and there but, a large scale, systematic way to keep track of them has not existed in the past. The highest number of VBAC birth order documented in medical literature in the past is after 5 cesareans. There are anecdotal stories of women having a VBAC after 4 Cesareans (look for a VBA4C story coming up on the podcast)!

More data is certainly needed to accurately judge the associated risks in VBA3+C. However, the data from the studies indicated in the table below implies that a TOLAC (Trial of Labor After Cesarean) should not be denied to women who want to pursue that option. The average rupture rate for women in all seven of these studies is just 1.2% which is so close to the 1% guideline ACOG sets forward as an "acceptable" risk rate for VBAC. Higher risks of rupture rates need to also be carefully considered against the substantial rising risks with subsequent cesareans.

What Do the Studies Show?

Since 2004, three newer VBAMC studies have much larger data sets providing more powerful conclusions than the smaller studies before them.

  • "Lin and Raynor (2004) found a rupture rate of 1.0% among 596 TOLACs after multiple cesareans, a data set almost six times as large as these other studies.

  • Macones (2005) found a rupture rate of 1.8% among 1,082 TOLACs, a data set about 10 times as large, and based on a multi-center study of 16 hospitals.

  • Landon (2006) found a rupture rate of 0.9% among 975 TOLACs, a data set over 9 times as large, and based on a multi-center study of 19 hospitals. It was also the only prospective study, unlike the other studies which used retrospective data." - (Plus Size Pregnancy, 2008)

Note also that the results of these three large studies fall mostly within the 1-2% rate that was found in the largest pre-2004 data. In fact, if only the most statistically powerful studies are considered from both time periods, the results show a uterine rupture risk largely between 1-2%.

Summary of the Largest VBAMC Studies

What Do I Do With This?

Your best choice going forward is to get your operative report from the hospital and doctors office that performed your cesarean and go through all of that information with several VBAC supportive providers in your area, Get their opinion, ask the right questions, and determine a plan moving forward that you are comfortable with and with a provider who is supportive of your desires.

Be sure to visit our podcast and listen to episode's 13 and 29 about women who went through some remarkable cesarean births and went on to achieve their VBA4C.

The summary of studies and referenced sources for this blog can be found here.


Are you over the VBAC myths and want solid data to back up the facts? Grab your FREE VBAC MythBusters guide here.

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