Uterine rupture risk in a VBA2C

[rareimer]

I saw an OB today that told me the risk of rupture was 3% for a VBA2C...i know i could probably find this statistic somewhere here if i really looked, but can't seem to at the moment.  Is this percentage accurate?

[Ms. B. Sprout]

Hi Robyn! Just as a comparison, an OB told me 7% last month when I consulted for a VBA2C. Of course, he also looked me straight in the eye and told me ACOG doesn't support VBA2C, so let's just say telling the truth is not his strong suit.

3% and 7% are both too high, from what I've looked at. The NIH consensus statement from March 2010 attempted to look at all the evidence and assess these types of risks. They classify the evidence assessing risk of rupture in VBAMC (not just VBA2C) as "low-grade," possibly because of small studies, inclusion of induced women or women with other risk factors, etc. Nevertheless, this is what they say:

Factors That Increase the Risk of Uterine Rupture

The following discussion of factors that affect the risk of uterine rupture is based on low-grade evidence.

Women with classical and low vertical uterine scars have an increased risk of rupture when compared to women who had a low transverse uterine incision at the time of cesarean delivery. Induction of labor has been associated with uterine rupture. However, due to variation among studies with respect to indications for delivery, induction protocol, agent and dose, and subsequent use of oxytocin, it is difficult to identify an absolute risk of uterine rupture associated with induction. The risk of rupture in women at term who have their labor induced is higher (1,500 per 100,000) than the risk of rupture if labor starts spontaneously (800 per 100,000). The risk of rupture may be increased in women who are induced at more than 40 weeks (3,200 per 100,000 at more than 40 weeks versus 1,500 per 100,000 at 37 to 40 weeks). There does not appear to be an increased risk of rupture with oxytocin augmentation of spontaneous labor.

A recently published meta-analysis revealed that increasing number of prior cesarean deliveries may increase risks of uterine rupture; two or more previous cesarean deliveries were associated with higher rupture rates (1,590 per 100,000) than one prior cesarean delivery (560 per 100,000). Other factors that may increase the risk of uterine rupture include unfavorable cervical status at the time of admission, obesity, inter-pregnancy interval of 18 months or less, single-layer closure for the initial cesarean delivery, infant weighing more than 4,000 grams, and giving birth in a low-volume hospital. Insufficient data are available to quantify the specific effects of these factors.

Also, on Plus-Size Pregnancy Kmom has a bunch of studies indexed in table form so you can see outcomes, rates of induction, etc. The research is a little dated -- I am not sure the last time she updated it. But it's still a valuable collection of studies at-a-glance, and it's some of the studies that NIH was looking at too I assume (unless there's some secret trove of studies that only medpros get to see).

Sooo, after looking at all this, I personally put the rate somewhere between 1% and 2%. For what that's worth.

VBAC Facts may also be helpful. I haven't poked around her site much yet, but this page looks informative.

[labortrials]

I wish I could remember where I saw this percentage and decided it seemed the most likely . . . perhaps it was something Marsden Wagner wrote, or it ws the Landon (2004) study . . . anyway, it goes from .5% VBAC to 1%+ for VBA2C.  However, I 'think' even this # is called into question because inductions and/or augmentations were not limited out of the study.

Sorry I'm fuzzy on my specifics right now . . .

[jenniro]

Kmom has a lot of great info, as pp said, http://plus-size-pregnancy.org/CSANDVBAC/NewestVBAMCresearch.htm#VBAMC Research Since The 2004 Guidelines

I also found this study published in 2009 http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.2009.02351.x/abstract  It is a meta-analysis and all the studies the authors use are in the body of the article.  There is a study, Caughey 1999, 134 TOL after 2 c-sections with a rupture rate of 3.7%  But looking at the 15 other studies, not one has a rupture rate for VBA2C higher than 2%.  So, I don't put much stock in one study with different results than everyone else.  Too bad OBs do