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Note: While this article was originally published in 2012, it received a complete face lift in 2021.

How many times have you heard, “Only 6% of uterine ruptures are catastrophic?”

Or “Uterine rupture not only happens less than one percent of the time, but the vast majority of ruptures are non-catastrophic?”

But what does that actually mean?

Does that mean only 6% of uterine ruptures are “complete” ruptures? Result in maternal mortality? Perinatal mortality? Serious injury to parent or baby?

This article will explain to you the difference between uterine rupture and uterine dehiscence, define catastrophic uterine rupture, as well as explain the source and meaning of that seemingly slippery 6% statistic.

Distinguishing between uterine rupture and uterine dehiscence

First, it’s important to understand what a uterine rupture is and how that differs from a uterine dehiscence. Uterine rupture fundamentally is a full-thickness opening through the uterine wall. During pregnancy, this involves two layers of the uterus, the myometrium (the uterine muscle) and the serosa (the outer uterine layer).

Sometimes uterine rupture can be referred to as a true or complete uterine rupture. I avoid that language because I find it muddies the waters and confuses birthing people. Either the uterine wall separates completely or it does not. If it does, it’s a uterine rupture.

Contrast that with a uterine dehiscence which is not a full-thickness separation. It’s often asymptomatic, does not pose any risk to the birthing parent or baby, and does not require surgical repair.

It is believed that many dehiscences go undiagnosed as the only time they would be identified is via an ultrasound, cesarean, or manual uterine exploration after vaginal delivery which is not recommended per ACOG guidelines.

Uterine dehiscence also goes by other names, such as an incomplete uterine rupture or uterine window, which I also avoid in order to reduce confusion particularly among birthing families.

How medical studies define uterine rupture

There is a lot of discussion about how medical studies define uterine rupture. The definition that they use ultimately impacts the uterine rupture rate that they report. If a study defines uterine rupture as any uterine “defect,” it is going to include dehiscence within that definition which inflates the reported uterine rupture rate.

All the studies that we reference here at VBAC Facts® clearly define uterine rupture as a full thickness separation of the uterine wall which distinguishes uterine rupture from uterine dehiscence.

Studies published around the 1980s or earlier typically combine the two events whereas modern studies typically do not.

However, it is always worthy to confirm the definitions spelled out in the methodology section of any VBAC study.

What does the 6% catastrophic uterine rupture statistic mean?

The statistic “Only 6% of uterine ruptures are catastrophic” is from the Guise (2010) Evidence Report which was the basis of the 2010 National Institutes of Health VBAC Conference. Here is the exact quote:

The overall risk of perinatal death due to uterine rupture was 6.2 percent. The two studies of women delivering at term that reported perinatal death rates report that 0 to 2.8 percent of all uterine ruptures resulted in a perinatal death.

In other words, of the birthing people who had uterine ruptures, 6.2% (1 in 16) resulted in perinatal deaths meaning the baby died either during labor or within 28 days of being born. When we limited the data to people delivering at term, as opposed to all gestational ages, the risk decreased to 0 – 2.8% (1 in 36).

The risk of catastrophic uterine rupture is very low

Using those figures, we are able to take a step back and ask ourselves, “What is the risk of a uterine rupture related perinatal death during a spontaneous labor after cesarean?” Some quick math, using the 0.7% risk of uterine rupture reported by Landon (2004), generates a risk range from 1 in 2,380 to 1 in 5,100.

Expressed another way, that is a 0.02% – 0.04% risk of uterine rupture related perinatal death.

No matter how you slice it, that is a pretty low absolute risk.

Nevertheless, as we often express within these discussions, it doesn’t matter how low the risk is when it happens to you. That small number represents the pain and loss of grieving parents. So while it’s important to clarify the low risk, we also have to acknowledge the human loss it represents.

The quality of evidence available on uterine rupture related perinatal mortality is not strong

Guise also noted, “Overall, the strength of evidence on perinatal mortality was low to moderate” due to the wide range of perinatal mortality rates reported by the studies included in the report.

In other words, the studies measuring uterine rupture related perinatal mortalities observed such divergent numbers that a “middle ground” or “average” number was hard to accurately generate. This means we still don’t have strong data documenting how often a uterine rupture results in a perinatal mortality.

I also appreciate their candor when they discuss what we know, what we don’t, and the best guesses we can make based on the available evidence:

Often, however, the data do not allow a direct estimate to calculate the numbers that people desire such as the number of cesareans needed to avoid one uterine rupture related [perinatal] death. The assumptions that are required to make such estimates from the available data introduce additional uncertainty that cannot be quantified. If we make a simplistic assumption that 6 percent of all uterine ruptures result in perinatal death (as found from the summary estimate), the range of estimated numbers of cesareans needed to be performed to prevent one uterine rupture related perinatal death would be 2,400 from the largest study, (204) and 3,900-6,100 from the other three studies of uterine rupture for TOL and ERCD. (10, 97, 205)

ACOG’s VBAC guidelines on planned VBAC and neonatal morbidity

We can also look to ACOG’s VBAC guidelines. While they don’t address uterine rupture related perinatal mortality specifically, likely because evidence strength is low, they do compare neonatal morbidity rates during planned VBAC versus elective repeat cesarean section:

ACOG 2019 VBAC Guidelines: Table 2. Composite Neonatal Morbidity From Elective Repeat Cesarean Delivery and Trial of Labor After Previous Cesarean Delivery in Term Infants

I want to highlight a couple things on this chart.

First, for most of these numbers, the risk is higher with a planned VBAC (which they refer to as TOLAC or trial of labor after cesarean), but the absolute risk – the likelihood of these events occurring – is still quite low during a planned VBAC or elective repeat cesarean delivery.

Let’s start with perinatal mortality, which captures fetal deaths after 20 weeks of pregnancy through infant deaths within 28 days of birth. Given that this outcome covers the largest span of time in comparison to the other outcomes, and in fact includes all of the other stillbirth and mortality outcomes within it, the rates here for this “umbrella” outcome are going to be the highest on the chart: 0.13% (1 in 769) for planned VBAC and 0.05% (1 in 2,000) for elective repeat cesarean delivery.

So what happens when we break out those numbers among the other subcategories representing smaller spans of time either before, during, or after birth? Neonatal mortality, which includes only deaths from birth to 28 days of life, is also low: 0.11% (1 in 909) for planned VBAC versus 0.06% (1 in 1,667) for elective repeat cesarean delivery.

Note that the risk is not zero for either measure or mode of delivery.

When we look at stillbirth, we can see that the risk of stillbirth before labor (antepartum) is low (0.10% planned VBAC vs 0.21% for elective repeat cesarean) as is the risk of stillbirth during labor (intrapartum) (0.01 – 0.04% planned VBAC vs 0 – 0.004% planned repeat cesarean).

Another outcome to note on this chart is HIE which stands for hypoxic-ischemic encephalopathy and describes an infant that has sustained brain damage as a result of oxygen deprivation. We can see that the absolute risk is again higher with planned VBAC, 0 – 0.89%, versus 0 – 0.32% in a planned repeat cesarean section, but the absolute risks are low.

Even though these numbers are from ACOG’s 2019 VBAC guidelines, they still reference the Guise 2010 Evidence Report as their source. I have two thoughts about this.

First, given that this data is from a summary report published in 2010, pulling from even older studies, it is possible that due to advances in health care, we could see lower rates of perinatal complications. This is an area where further research is needed to reflect current available technologies and practices.

Second, I chuckle at the fact that ACOG’s 2019 VBAC guidelines cite a nine year old report given that some conferences insist speakers limit their citations to only the prior five years. We simply do not have that luxury with the VBAC research. If you are a conference planner, I urge you to reconsider this requirement. I digress.

The source of the confusion about “catastrophic uterine rupture”

But let’s circle back to the 6% statistic. Where did the confusion about this number and catastrophic uterine rupture emerge?

I think it’s a combination of blurring what defines a uterine rupture versus uterine dehiscence as well as a lack of clarity on how studies define uterine rupture and the ambiguous language (“catastrophic uterine rupture”) we use to describe this heartbreaking event.

The fundamental problem with this 6% statistic is that some people have misinterpreted it to mean that only 6% of reported uterine ruptures are actual uterine ruptures.

In other words, they hear a rate of uterine rupture, like 0.7% from the Landon (2004) study, and believe that only 6% of those events are “true” uterine ruptures and the rest are uterine dehiscences.

Clearly, this leaves them with the impression that the risk of uterine rupture is truly miniscule.

How often uterine rupture and uterine dehiscence occur

However, one of the largest VBAC studies, Landon (2004), which distinguished uterine rupture from uterine dehiscence, reported the rate of each to be 0.7% or 1 in 143 planned VBACs.

Keep in mind that this reflects the outcomes of 18,000 who labored after a cesarean, 63% of which were either induced or augmented. (Yes, you can induce or augment a labor after cesarean.)

When they broke out the rate of uterine rupture for those who labored spontaneously after cesarean – without induction or augmentation – the uterine rupture risk decreased to 0.4% or 1 in 240 planned VBACs.

This is the number I often use when discussing uterine rupture because – through isolating just spontaneous labor after cesarean – it gets us as close as possible to a “baseline” risk of uterine rupture.

Let’s be clear about “catastrophic uterine rupture”

Finally, I think the best way to avoid confusion about “catastrophic uterine rupture” is to use very clear language when talking with birthing families: Research has found that 2.8 – 6.2% of uterine ruptures result in an perinatal mortality which works out to an overall risk of 1 in 2,300 to 1 in 5,100* during a planned labor after cesarean, which drops even more if the labor is not induced or augmented.

Using vague language like “catastrophic uterine rupture” – which provides us a level of comfort by avoiding outright that someone died – only adds to the uncertainty that many birthing families feel when discussing the rate and risk of uterine rupture.

Or even more, it contributes to erroneous beliefs among parents about the “true” incidence of uterine rupture, or the severity of its outcomes, leaving them with the false impression that the risk of uterine rupture is actually much lower than reported in the research.

This overarching lack of clarity is a barrier to true informed consent. Easy, clear, and straightforward language will mitigate this ongoing challenge of effectively communicating obstetrical risk to birthing families.

The safety of VBAC and the risk of uterine rupture

So what does all this mean in terms of the safety of VBAC and the risk of uterine rupture?

Looking at the totality of the evidence Guise (2010) asserts both VBAC and repeat cesarean are reasonable options which often result in healthy infants:

VBAC is a reasonable and safe choice for the majority of women with prior cesarean. Moreover, there is emerging evidence of serious harms relating to multiple cesareans… The occurrence of maternal and infant mortality for women with prior cesarean is not significantly elevated when compared with national rates overall of mortality in childbirth. The majority of women who have TOL [trial of labor] will have a VBAC, and they and their infants will be healthy. However, there is a minority of women who will suffer serious adverse consequences of both TOL and ERCD [elective repeat cesarean delivery].

We can also look to ACOG’s national guidelines which have maintained for years that VBAC is a safe, reasonable, and appropriate option for most people with a prior cesarean. As a result, they encourage VBAC access and support all Level 1 hospitals to offer labor after a cesarean.

Take home message

Now you know the difference between uterine rupture, uterine dehiscence, and catastrophic uterine rupture. You also know that the 6% statistic refers to uterine rupture related perinatal mortalities. However, that number refers to all gestational ages whereas the risk of uterine rupture related perinatal mortality among term uterine ruptures was only 2.8%.

It’s vital to understand the terminology used relative to uterine rupture in order to make sense of not only medical studies, but also to facilitate conversations between parents and clinicians.

I also think it’s very important for people to use specific words whose definitions are clear instead of phrases like “catastrophic uterine rupture” that could mean multiple things to multiple people. I have found it especially confusing to birthing families.

As tough as it may be, unambiguous terms like “uterine rupture related perinatal mortality” might be the most understandable to parents.

In this article, we highlighted the outcome of uterine rupture related perinatal mortality – the fear of many parents. At the end of the day, and in light of the increasing risks associated with multiple repeat cesarean sections, VBAC is still considered an evidence based choice and should be available to parents who wish to peruse this safe and reasonable option. The evidence and national guidelines support it.


Diving into the math

*  I received a question from a reader on how I calculated the 1 in 2300 – 1 in 5100 range for uterine rupture related perinatal mortality, so I wanted to share that math here for others that are interested.

What I did was multiply the 0.7% risk uterine rupture by Landon by 2.8% which is 0.0196%. That’s the incidence per 100: 0.0196 per 100.

To turn that into a 1 in ______ ratio, you divide 0.0196/100. That gives 5102 which I rounded to 5100, so 1 in 5100.

Do the same process with 6.2%:

6.2% * 0.7% = 0.04340%
Rate: 0.04340 per 100
Create the ratio of 1 per _____ by dividing 0.0434/100 = 2304, round down and that’s 2300
Final ratio: 1 in 2300

So using the uterine rupture rate of 0.7% and the 2.8 – 6.2% uterine rupture related perinatal mortality rate range, we can calculate the risk of uterine rupture related perinatal mortality in a given planned VBAC to be 1 in 2300 – 1 in 5100.

Now, we could crunch these numbers using different uterine rupture figures, but given the incidence of induction and augmentation, I thought the 0.7% was a good overall number.

 

Resources Cited

American College of Obstetricians and Gynecologists. (2019). ACOG Practice Bulletin No. 205. Vaginal birth after cesarean delivery. Obstetrics & Gynecology, 133(2), e110-e127. https://journals.lww.com/greenjournal/Abstract/2019/02000/ACOG_Practice_Bulletin_No__205__Vaginal_Birth.40.aspx

Guise, J.-M., Eden, K., Emeis, C., Denman, M., Marshall, N., Fu, R., . . . McDonagh, M. (2010). Vaginal Birth After Cesarean: New Insights. Rockville (MD): Agency for Healthcare Research and Quality (US). http://www.ncbi.nlm.nih.gov/books/NBK44571/

Landon, M. B., Hauth, J. C., Leveno, K. J., Spong, C. Y., Leindecker, M. S., Varner, M. W., . . . Miodovnik, M. (2004). Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery. New England Journal of Medicine, 351, 2581-2589. https://doi.org/10.1056/NEJMoa040405

 

What do you think?
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What do you think? Leave a comment.

21 Comments

  1. Jen, love this article and using it as a great reference! Can you explain the statistics for perinatal mortality after uterine rupture. ” research shows that 2.8-6.2% (1 in 2,380 to 1 in 5,100). Could you explain all the numbers that go into this equation. I realize it is based on the .4% risk of uterine rupture when IOL and induction is taken out. I apologize for this lack of ignorance on my part. Numbers are not my strong suit.

    Reply
    • Hi Jennifer!

      This is a great question because the math can be confusing and I’m sure others have similar questions.

      What I did here was multiply the 0.7% risk uterine rupture by 2.8% which is 0.0196%. That’s the incidence per 100: 0.0196 per 100.

      To turn that into a 1 in ______ ratio, you divide 0.0196/100. That gives 5102 which I rounded to 5100, so 1 in 5100.

      Do the same process with 6.2%:

      6.2% * 0.7% = 0.04340%
      Rate: 0.04340 per 100
      Create the ratio of 1 per _____ by dividing 0.0434/100 = 2304 (opps, I see a typo in the article as I have it written there as 2380, so I will fix that)
      Final ratio: 1 in 2304

      So using the uterine rupture rate of 0.7% and the 2.8 – 6.2% uterine rupture related perinatal mortality rate range, we can calculate the risk of uterine rupture related perinatal mortality in a given planned VBAC to be 1 in 2300 – 1 in 5100.

      Now, we could crunch these numbers using different uterine rupture figures, but given the incidence of induction and augmentation, I thought the 0.7% was a good overall number.

      Did that help?

      Reply
  2. Hi,

    This addresses VBAC after 1 caesarean. I was very lucky to deliver vaginally (a perfect birth, thank G-d!) after my first 2 caesareans. But since then I have had 2 more. What resources can you point me to that discuss my chances of a healthy natural birth after 4 caerareans?

    Thanks so much.

    Reply
    • Hi Esther,

      The truth is, there isn’t much evidence on vaginal birth after multiple cesareans. Go here to learn more.

      Reply
  3. Totally agree that the confusion here comes down to the use of the word ‘catastrophic’. If, by ‘catastrophic’, folks mean ‘someone dies’, this is where the waters get muddied (in the case of the Landon, 2004 stats, anyway). It is so important to mind one’s language with regards to stat discussion.

    In South Australia, our government perinatal guidelines reference a VBAC rupture rate between 0.5% and 1% (stating that “most series” report this). I wondered if you could point me in the direction of the series which report a rupture closer to 1%? I am keen to know if these reports include dishiscences as well as complete ruptures.

    Thank you kindly!

    Reply
    • Hi Tessa,

      Here are two sources:

      Landon (2004) reported a uterine rupture rate of 1.0% among induced labors.

      Mercer (2008) reported a rate of 0.87% among spontaneous labors and 1.37% among induced labors.

      Hope this helps!

      Jen

      Reply
  4. These statistics are only relevant to hospital birth. The neonatal mortality rate following uterine rupture is low +/- 6% IF DELIVERY IS WITHIN 16-28 MINUTES from the time of rupture. Which is nearly impossible if transporting from home, even if you live near the hospital. After this timefram has passed, neonatal mortality rates rise to 60%. Do the research. This kind of article is dangerous and irresponsible.

    Reply
    • Cara,

      Absolutely. I reference the 17 minute time frame in the article above which is one of the risks of homebirth.

      Best,

      Jen

      Reply
  5. I had to have a c section with my first child. There were complications, as my cervix swelled, I stopped dialating, and she went into distress. Afterwards, they realized she was stuck. The c section was needed but now I am pregnant with my second and want to do a VBAC. I met with my new doctor today, as we recently moved. I felt she was trying to sway me to have another c section. She told me I was at risk for things to go wrong during VBAC because of the complications with my first birth. I am concerned about the risks during a VBAC. I feel confused and uncertain. Any comments are appreciated.

    Reply
    • Amber,

      I’ve posted your question here.

      Best,

      Jen

      Reply
    • Amber,

      I shared your comment over on Facebook. Join us there to view the responses.

      Best,

      Jen

      Reply
  6. Hmmm,always something to think about. How about we prevent unnecessary c-sections in the first place. We could help families to make decisions based on fact instead of fear. We sometimes feel like we can have all of the answers, but reality is that not all births are picture perfect,even in the best of circumstances.

    Reply
    • Joanne,

      I completely agree. We need to prevent unnecessary primary (and repeat) cesareans. One of the things that can make that happen is for women to be aware of how the risks increase in post-cesarean pregnancies regardless of the mode of delivery, and especially if a mom has multiple repeat cesareans. Unfortunately, primary and repeat cesareans are generally viewed as benign by the public.

      Warmly,

      Jen

      Reply
  7. I was with a woman who wanted to have a VBAC at home. She was 8cm when she insisted ‘something was wrong’. An ambulance was called, she was transported to hospital and everyone flew into action. Surgery determined her baby had delivered into her abdominal cavity but both mother and baby were fine. The surgery was performed about 1.25 hours after she initially felt something was wrong. The lesson for me . . . always listen to the mother!

    Reply
  8. As much as I’m a proponent of home and natural birth, I think it’s pretty dangerous to do a first VBAC at home–should there be a uterine rupture, you could lose both mother and baby, and there really isn’t time to get to the hospital in that situation. You can still have all those things in hospital with a CNM or other provider willing to give the support necessary.

    Reply
  9. Becky, I’m not sure you can so simply draw that conclusion. Lack of unnecessary interventions, freedom of movement, lack of restrictions of food and fluids, close attendance of the hb midwife, and overall greater level of comfort of the mother very likely would decrease the incidence of complications in the first place. Furthermore, close observation of the mw to spot issues early on and call ahead while in transport to hospital can decrease risks.

    Reply
    • “Lack of unnecessary interventions, freedom of movement, lack of restrictions of food and fluids, close attendance of the hb midwife, and overall greater level of comfort of the mother very likely would decrease the incidence of complications in the first place.”

      Do you have any evidence for any of this? The one difference might be the lack of augmentation or induction at home, but homebirths may be more likely to be prolonged labors, which is also a risk factor for a uterine rupture.

      In any case, *if a rupture happens,* we already know that time is of the essence to prevent a death or brain damage. Being a half or more away from the OR instead of 10 minutes absolutely will affect the mortality rate.

      Reply
    • Katie thats not true a uterus rupture is not something that can be prevented with lack of intervention and food in take during child birth at home. I’ve had it happen and me and my son are happy and well thanks to the doctors and nurses that acted quickly. I’m sure if I was home my life would be very different. I think your statement is quite ignorant and you are unaware of what its like to endure that kind of trauma. And just so you know the time it takes for an ambulance to get you from your home to a hospital could be much to long. You or your baby could be one of those catastrophic ruptures. I’m greatful for my life and my sons life. Its all because of the doctors, nurses and surgeons in a facility capable to handle those kind of problems.

      Reply
      • Stephanie, you said “uterus rupture is not something that can be prevented with lack of intervention”. That is mostly false (I use “mostly” instead of “absolutely” only due to the fact that ruptures cannot be fully prevented in any pregnant woman’s circumstances). Interventions such as inductions, epidurals, anesthesia and coached pushing CAN have an impact on UTERINE rupture rates. The less the body is messed with while in labor (or to put it into labor), the more likely things will turn out well. I’m sorry that you had a rupture, but the fact of the matter is just because YOU felt better to have your vbac in a hospital (I am assuming it was a vbac, but uterine ruptures do occur in vaginal deliverers without have prior c/s, so I can’t be sure) doesn’t mean the risks are higher at home or that interventions don’t cause more ruptures (possibly causing more ruptures than the lives they save even, possibly). The differences in a woman’s comfort and lack of interventions experienced at home do have an impact. And who is to say that the increased stress in a hospital setting, that causes increased adrenaline, wouldn’t contribute to a rupture? The factual statistics aren’t there for all of this yet. But there has been some proof that interventions can contribute to bad outcomes in vbacs and in TOLAC.

        Reply
  10. Nice article. It is important for parents to keep in mind that this mortality rate is based on babies born in hospital. The mortality rate for rupture at a homebirth would likely be much higher, since time is so much of the essence when a rupture occurs.

    Reply

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Jen Kamel

Jen Kamel is the CEO and Founder of VBAC Facts® whose mission is to increase access to vaginal birth after cesarean (VBAC). VBAC Facts® works to achieve this mission through their educational courses for parents, online membership for professionals, continuing education trainings, and consulting services. As an internationally recognized consumer advocate, Jen speaks at conferences across the world, presents Grand Rounds at hospitals, advises on midwifery laws and rules that limit VBAC access, educates legislators and policy makers, and serves as an expert witness and consultant in legal proceedings. VBAC Facts® envisions a time when every pregnant person seeking VBAC has access to unbiased information, respectful providers, and community support so they can plan the birth of their choosing in the setting they desire.

Learn more >

Jen Kamel

Jen Kamel is the CEO and Founder of VBAC Facts® whose mission is to increase access to vaginal birth after cesarean (VBAC). VBAC Facts® works to achieve this mission through their educational courses for parents, online membership for professionals, continuing education trainings, and consulting services. As an internationally recognized consumer advocate, Jen speaks at conferences across the world, presents Grand Rounds at hospitals, advises on midwifery laws and rules that limit VBAC access, educates legislators and policy makers, and serves as an expert witness and consultant in legal proceedings. VBAC Facts® envisions a time when every pregnant person seeking VBAC has access to unbiased information, respectful providers, and community support so they can plan the birth of their choosing in the setting they desire.

Learn more >

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