myth versus reality

Myth: Risk of uterine rupture doesn’t change much after a cesarean

myth versus reality

1/18/12 – The difference in uterine rupture (UR) rates between unscarred and scarred uteri is significant: 1 in 14,286 in an unscarred uterus and 1 in 156 in a scarred uterus.  Another way to express this is: 0.7 in 10,000 (0.007%) in an unscarred uterus and 64 in 10,000 (0.64%) in a scarred uterus.  This 91 times greater risk does not mean that the risk of UR is so large in a scarred mom, it’s that it’s so very, very small in an unscarred mom.


I came across a couple different bits of (mis)information the past day that have really concerned me. In both situations, people, one of whom is a certified professional midwife (CPM), give false information regarding how a cesarean affects one’s risk of uterine rupture in future pregnancies.

First, a women with a prior cesarean asks for uterine rupture rates after a cesarean, “preferable one with stats” on Facebook. One woman gives this reply:

… almost all cases the risk of rupture is less than one percent, even after multiple sections, or special scars such as an inverted T. The risk is roughly double what it is for an unscarred uterus, but considering the tiny numbers it doesn’t really make a difference, especially since the vast majority of ruptures are not catastrophic in nature, something that is not differentiated in study results.

(There are several things that are false in this statement, but I’ll save those for another post.) Then later in the day, I came across this comment from a CPM’s website:

Will you do a vaginal birth after cesarean?
Yes. Studies have shown that there isn’t much of a difference in uterine rupture rates in someone that has had a previous cesarean and someone who has never had one. A lot of my clients are VBAC’s or attempted VBAC’s. I am completely comfortable with this.

Both of these representations of uterine rupture after a cesarean are erroneous. It’s especially disturbing that a midwife who is counseling VBAC moms and attending their births at home, is giving her clients grossly incorrect information. The risk of a uterine rupture does much more than double after a cesarean as the risk in an unscarred uterus is infinitesimal in comparison to a scarred uterus.

Comparing the risk of uterine rupture: Prior cesarean vs. no prior cesarean

I started looking around and quickly found Uterine rupture in the Netherlands: a nationwide population-based cohort study (Zwart, 2009) which contains the data I needed to compare the rates of rupture in unscarred vs. scarred uteri. You can read the study in its entirety here.

This study included 358,874 total deliveries, making it “the largest prospective report of uterine rupture in women without a previous cesarean in a Western country.” It also differentiates between uterine rupture and dehiscence which is really important because we want to measure the rate of complete rupture. (Remember how the lady from Facebook made the statement, ” the vast majority of ruptures are not catastrophic in nature, something that is not differentiated in study results.” That portion of her statement was also false.)

Zwart (2009) looked at 25,989 deliveries after a cesarean and found 183 ruptures giving us a 0.64% uterine rupture rate or 64 per 10,000 deliveries. 72% of those ruptures occurred in spontaneous labors. Of the 183 ruptures, 7.7% resulted in infant deaths representing 14 babies dying. This gives us a rate of infant mortality due to uterine rupture after a cesarean of 0.05% or 5 in 10,000 deliveries.

Zwart also looked at 332,885 deliveries with no prior cesarean resulting in 25 ruptures giving us a 0.007% uterine rupture rate or .7 per 10,000 deliveries. 56% of ruptures occurred in spontaneous labors. Of the 25 ruptures, 24% resulted in infant deaths representing 6 babies dying. This gives us a rate of infant mortality due to uterine rupture in an unscarred uterus of 0.0018% or 0.18 in 10,000 deliveries.

This study found that the risk of uterine rupture is 91 times greater in a woman with a prior cesarean vs. a woman without a prior cesarean. Not double, not similar, but 91 times greater.

It is important to note that, “severe maternal and neonatal morbidity and mortality were clearly more often observed among women with an unscarred uterine rupture as compared to uterine scar rupture.” Meaning, if an unscarred mom ruptures, her baby is more likely to die than a scarred mom. We see this when we compare the 24% of unscarred ruptures that resulted in an infant death vs. the 7.7% of scarred ruptures that resulted in an infant death which represents a 3 fold greater risk.

However, due to the fact that uterine rupture occurs more frequently in a scarred uterus, the risk of infant mortality due to uterine rupture after a previous cesarean was 27.8 times greater than the risk of infant mortality after a rupture in an unscarred uterus.

In other words, while ruptures in unscarred uteri are more deadly to infants, more infants die due to ruptures in scarred uteri because they occur more frequently.

OBs are often vilified (rightfully so) for giving women inflated rates of uterine rupture and I’ve documented several examples here: Another VBAC Consult Misinforms, Scare tactics vs. informed consent, Hospital VBAC turned CS due to constant scare tactics, and A father says, Why invite the risk of VBAC?.

As a result, women seek out midwives thinking that they will be a source of accurate information and judicious support. But what happens when your midwife tells you that your risk of uterine rupture has not increased as a result of your prior cesarean section? If you have done your homework, hopefully you find another midwife fast. I would really question the skills and knowledge of a midwife who is so unknowledgeable on the risks of VBAC and yet attends VBAC births in an out-of-hospital setting.

But suppose your haven’t done your homework, you trust your midwife, and you move forward with your plan to have a VBAC at home based on the incorrect statistics she supplies. I can’t begin to imagine the rage I would feel if I decided to have a home VBAC based on false information provided by my care provider, and then the unimaginable happened, and I ruptured, and then I learned the truth: that my risk of uterine rupture increased 91 times as a result of my prior cesarean. I would be beyond angry. I would feel so betrayed.

It’s unfortunate when a woman chooses a mode of delivery based on false information. Whether it’s a a woman deciding to have a repeat cesarean due to the exaggerated risk of uterine rupture provided by her OB or a woman deciding to have a (home) VBAC due to her midwife playing down and underestimating the risk of uterine rupture. It is just as bad to minimize the risk of uterine rupture as it is to inflate the risk.

While the risk of rupture in a spontaneous labor after one prior low transverse cesarean is comparable to other obstetrical emergencies, it is important for women weighting their post-cesarean birth options to know that their risk increased substantially due to their prior cesarean. It is important for them to understand the risks and benefits of VBAC vs. repeat cesarean. It is important for them to have access to accurate information and be able to differentiate between a midwife’s/blogger’s/doula’s/birth advocate’s/person on Facebook’s hopeful opinion vs. documented statistics.

I implore those who interact with, and have impact on, women weighing their birth options: do not pass along information, no matter how great it sounds, if you don’t have a well-designed scientific study supporting it. If you hear a statistic you would love to use and share, just ask the person who gave you this information,”What is the source?” and use the citation anytime you quote the statistic. But if the person doesn’t have a well-designed scientific study, be wary and don’t use the stat. This way, we can reduce the rumor and increase the amount of good information on the Internet. I know, a lofty goal.

Read more birth myths debunked including Lightning strikes, shark bites, and uterine rupture and Myth: Unscarred mom induced (with Pit) as likely as VBAC mom to rupture.


Zwart, J. J., Richters, J. M., Ory, F., de Vries, J., Bloemenkamp, K., & van Roosmalen, J. (2009, July). Uterine rupture in the Netherlands: a nationwide population-based cohort study. BJOG: An International Journal of Obstetrics and Gynaecology, 116(8), pp. 1069-1080. Retrieved January 15, 2012, from

rutpures in scarred uteri

22 thoughts on “Myth: Risk of uterine rupture doesn’t change much after a cesarean

  1. VBAMHopeful

    I was wondering if you have any information on the risk of uterine rupture after myomectomy as it compares to VBAC? I had a 3.3cm intramural fibroid removed from the fundus. My uterus was not cut all the way through though it was deeply embedded. It seems to me that VBAM is even more discouraged than VBACs. Why is this? Is it because it was a vertical incision? This is confusing to me because it seems like a vertical incision on the body of the uterus is completely different than an incision on the top of the uterus. I have also heard that it may be because contractions originate from the fundus. But if that is true wouldn’t it mean that the intensity of the contraction builds to the lower part of the uterus. From the medical literature it looks like the lower part of the uterus is where rupture is most often seen, and it isn’t always along the c-section scar. I have tried to find actual experiences of women who have experienced rupture but the only ones I have found were not during labor but rather several weeks prior to when a c-section would have been scheduled. So no matter what they wouldn’t have avoided a rupture. If your scar holds up until the point of TOL, wouldn’t it stand to reason that its integrity has been sufficiently proven to make a TOL an option just as much as C-section?

    1. Jen Kamel Post author


      Myomectomies vary a lot person to person due to individual circumstances. Your best bet is to review your operative report with a few VBAC supportive doctors/midwives in your area and get their opinion.

      The lower part of the uterus is where most ruptures occur in scarred uteri because the rupture is occurring along the cesarean scar. Among the very rare uterine ruptures in unscarred women, ruptures occur all over the uterus.

      While uterine rupture can occur before labor begins, it’s exceedingly rare. Over 99.95% of ruptures occur during labor. Read more here.

      So labor does put more stress on the uterus and if there is a weakness in the uterus, like an existing scar, that increases the risk of uterine rupture. That’s why even though scarred uteri hold up during pregnancy, there is an increased rate of uterine rupture in comparison to unscarred uteri.

      This is an area of unknown risk because not every combination of myomectomy scars have been studied in terms of uterine rupture.

      So, I recommend talking with some doctors/midwives in your area and getting their opinion.

      Ultimately the choice is yours.



      PS – If you would like to talk to other women who have had myomectomies, come post a question on the VBAC Facts Facebook page.

      1. VBAMHopeful

        Can you direct me to information that forms the basis or supports the thinking that vertical and classical incisions are at a higher risk for uterine rupture than low transverse? I have searched and searched but the only info that I can find just makes the statement that they are riskier and doesn’t direct to any studies or concrete evidence. I think the risk is generally stated as approximately 9%. Just wondering where this is coming from.

        1. Jen Kamel Post author

          Hi there!

          Classical (high, vertical) incisions go into the upper part of the uterus which does all the work during labor. The thought is, if that upper part (the fundus) is cut, it’s more likely to rupture during labor. Very few women have classical incisions, so it’s been insufficiently studied which means we don’t have super great numbers quantifying the risk of rupture among these scar types. ACOG says that parents with classical incisions are not “generally” considered candidates for VBAC.

          Low vertical incisions are OK for VBAC per ACOG because they are in the lower uterine segment which is associated with lower rates of uterine rupture.

          If you want to dig deeper, I cover this in great detail and so much more in my online workshop for parents.




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