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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.

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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.

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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 http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.2009.02136.x/full

rutpures in scarred uteri

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

  • This is so, so important. Women need FACTS, they don’t need to be told what they want to hear! Thank you for highlighting this.

  • Regina

    I think what you’re seeing here is the retelling of information given at the VBAC symposium at the National Institutes for Health last year. There were clearly worded statements made by researchers and physicians stating that what they analyzed showed that there were not significant differences in the outcomes of first time mothers, VBAC mothers, or mothers birthing vaginally after multiple cesareans. I don’t have the studies to which they referred, however; you can go to the NIH and review their information presented during those days of discussion.

    • Jen Kamel

      Regina,

      I was at the NIH VBAC conference. It was awesome and there was a lot of great information shared. However, no one ever said that the risk of UR in a VBAC mom was “similar to” or “double” the risk of an unscarred mom. There is not one piece of research to support that false claim. You can watch all the presentations from the NIH here.

      I believe the study you are referring to was the Smith (2002) study which I have listed in my bibliography. Smith stated the risk of infant death during a VBAC attempt is “similar to the risk” of infant death during the labor of a first time mom.

      I don’t know how someone can confuse the risk of infant death with the risk of uterine rupture.

      I hope you will help me in dispelling this myth by forwarding this article to anyone who repeats it!

      Warmly,

      Jen

  • Jessica W.

    ok here is a question i really need to ask.
    I have had two c sections within 2 years (jan 2010, and Feb 2011). I have two different scars because they had to cut higher the second time around.

    I dont plan on having another kid anytime soon but you know how things tend to go.

    My question is what would be my chance of having a successful vbac if I were to get pregnant now and within 9 months (a year and 9 months after second section) have another baby. I know the longer I wait the safer it is and thats why I dont plan on having another kid for another at least year or so (another question is what about the 2 year time frame)

    I hope this made sense on what I was trying to ask.

    The reason for the second section was because I gave in and the doc wanted me to have a section (to cover his but more than anything) I had gestational diabetes and because of that the doc didnt want me to go full term.
    I honestly dont know what to think. And I think its messed up that because of an idiot doctor with my first child I am now almost FORCED to have csections for the rest of my kids and now i am LIMITED on how many kids that MY body can have.

    HELP lol!
    Thanks

  • Details

    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.

    Okay, so if 72 % of those ruptures (132)occurred in spontaneous labors, how many of the 25,989 woman had spontaneous labors and what is the rate of rupture for spontaneous labour during VBAC?

    Conversely what is the rate of rupture when a VBAC TOL is induced or augmented? 51 over what?

    I’m also intersted in the method of induction, but I understand that information wasn’t available.

    • Jen Kamel

      Details,

      < >

      Zwart did not provide the number or percentage of women who had spontaneous labors vs. induced labors. In trying to find how many labors are typically induced in the Netherlands, I found a study which stated, “In The Netherlands induction rates have remained stable over the last decade at approximately 15%” (Verhoeven, 2009). Since the induction rate has been stable, and this study included 97% of births in The Netherlands between August 1, 2004 and August 1, 2006, I felt comfortable using this 15% rate of induction to calculate the rate of uterine rupture in induced, unscarred women. Read more about induced, unscarred rupture vs. scar rupture.

      < >

      I would love that data too. Unfortunately, for whatever reason, Zwart did not break out the data in that manner.

      < >

      Zwart utilized multiple methods of induction: cervical prostaglandins (sulproston, dinoproston, and misoprostol aka Cytotec), oxytocin (Pitocin) and mechanical dilatation. Prostaglandin “dosages ranged from 0.5 to 2.0 mg with a minimal interval of 4 h in between,” but they do not provide the dosages of the women who ruptured.

      You can always email Zwart and ask these questions! Please share any additional information you receive!

      Warmly,

      Jen

  • Details

    Also in regard to your comment. “I don’t know how someone can confuse the risk of infant death with the risk of uterine rupture.” The general public believes that uterine rupture equals infant death 100% of the time. That is the first myth that needs to be dispelled!

  • kay

    I just want to say- just because there is a very low percentage of those who rupture- trust me you do NOT want to be the one it happens to.

    I had my 4th child. No previous sections. My uterus ruptured, placenta separated, and bladder was ripped in HALF!!!! My surgery consisted of a hysterectomy (after doc tried to save my uterus), 4 units of blood, bladder repair, suprapubic catheter for 7 wks and i did not get to see my baby for 9 days. NOT ONCE!!!

    He was pulled out just in time, he was not breathing and had to be intubated. He was careflighted to another hospital. I was told he would have brain damage.

    Thankfully we both miraculously healed and have NO lasting effects. Most women with ruptured uteruses alone dont come out this well.

    But dont poo it off as just docs trying to scare you. These are SERIOUS complications that can happen. and it typically happens from a previously scarred uterus.

    If you wish to risk your childs life, thats your business, but its not something to be taken lightly.

    • Jen Kamel

      Kay,

      I am so sorry about your rupture and the fact that you were unable to see your son for so long. I’m glad the doctors acted quick and that you and your son have no long-term complications.

      Who is poo-pooing the risk of rupture? Perhaps you’re unfamiliar with this website: http://vbacfacts.com/2012/12/07/some-people-think-im-anti-thispro-that-my-advocacy-style/. I have discussed uterine rupture at great length: http://vbacfacts.com/category/vbac/uterine-rupture/.

      I am not someone who poo-poos risks. In fact this article was written in response to the urban legend that rupture rates don’t vary between scarred and unscarred moms. This myth, which this article debunks, very much minimized the risk of rupture.

      Are you suggesting that all women have cesareans to circumvent unlikely and unpredictable events like uterine rupture or placental abruption? Cesareans come with their own risks: http://vbacfacts.com/2012/12/09/why-cesareans-are-a-big-deal-to-you-your-wife-and-your-daughter/. So to suggest that VBACs are only for women who choose to risk the lives of their children is inaccurate.

      Yes, the risk of rupture in an unscarred woman is extremely low, but that does not mean it is zero. That is not minimizing the risk. That’s simply a statement of fact.

      I am sincerely sorry you were the statistic.

      Warmly,

      Jen

  • Hi Jen,
    Do you know what the UR risk is for an unscarred mom while on Pitocin?

    • Jen Kamel

      Jamie,

      Ah yes, that is another persistent myth – that an unscarred, induced mom has the same risk of rupture as a scarred mom. The risk of rupture in an induced, unscarred mom is about 1 in 4,500 – still pretty darn rare. Read more here.

      Warmly,

      Jen

  • Jeannie

    Jen,

    So I’ve been going back and forth on what to do about my labor and delivery with #2. I’m 5 months along. I had my first 2.5 years ago. Was supposed to be a midwife attended home birth. We had to transfer and I ended up having a CS with a J incision (he was OP and over 10 pounds).
    I can’t really find an OB who will assist in vbac and I’m cautious about HBAC with midwives.
    This article is kind of scaring me into the “schedule the surgery” zone.
    Thoughts?

    • Jen Kamel

      Jeannie,

      Congratulations on your pregnancy!

      I wrote this article to debunk the oft repeated myth that the rate of uterine rupture doesn’t change (much) after a cesarean. While the risk does increase greatly, this does not mean that the risk of uterine rupture is excessive during a VBAC nor that VBAC is dangerous. When women believe that the risk of uterine rupture during a VBAC is similar to an unscarred mom, they are not able to make an informed decision about their birthing options. Women are entitled to fair and accurate data and that is what this article is about.

      To be clear, the rate of uterine rupture after one prior low transverse cesarean has been well documented to be 0.5% – 1% depending on a variety of factors. This is comparable to the rate of other dire obstetrical emergencies that hospitals offering L&D are able to address and most moms don’t give a thought to. But uterine rupture is marketed to the public in such a way that people really believe that it’s more serious or more likely to occur than other complications that even mothers without a prior cesarean are subject to. Yet the American College of OB/GYNs and the National Institutes of Health maintain that VBAC is a safe and reasonable option for which most women are candidates. Remember, we must not only look at the risks and benefits of VBAC, but these need be weighed against the risks and benefits of cesareans. (Here are pamphlets from ACOG and the Power to Push for you to review.)

      The risk changes with a J incision. The research on “special scars” (which include classical/high vertical scars, J & T incisions) is very limited. We have a handful of studies reporting a wide range of rates. Further, these studies included small sample sizes and did not control for important factors such as induction and augmentation. So we really don’t know that the risk is for women who want to VBAC with a special scar (also referred to as a VBASSC.) Any woman planning a VBASSC must weigh the unknown risks of VBASSC with the known risks of multiple repeat cesareans and factor in her intended family size.

      ACOG says that women with special scars are not “generally” candidates for VBAC and thus they leave the door open for women who do want to VBASSC. There are hospital based care providers who attend VBASSC but they are few and far between and you may have to travel in order to birth with them. Birthing at home comes with less rules, less regulations and more freedom to birth how you want, but carries its own set of risks.

      This is a decision that you can only make for yourself. As you collect information, be sure to ask for sources when people give you statistics. Unfortunately, there is a lot of misinformation on the internet which is what fueled my whole Birth Myths,m series.

      What area are you in? Perhaps I can post on Facebook to see if possibly there is a care provider in your area who you have not yet talked to.

      Best,

      Jen

  • Nikki Gundlach

    Hi Jen,

    I was directed to you by Rebecca, because I in really in need of vbac support.. I am living in Germany, and NO care provider, hospital or midwife will allow me to have a vba3c. I am currently nearly 15 weeks pregnant after having 3 completely unnecessary, very traumatic cesareans. I just had a meeting with the most progressive hospital for birth in the city.. They will even allow a vba2c, but not 3. They stated the risk then becomes so much higher for rupture.. Even though the dr. said in her own words “the risk is low” she also said my scar looks great, and the placenta is not anywhere near the scar.. I am being forced into having a repeat cesarean or having a UCa3c, which I really dont feel comfortable with.. Is there any way you could help me with ideas or help or even connect me with someone here in Germany? I have been searchng for 10 weeks with no luck.. I feel frustrated and lost.. Thank you..

    Nikki

  • [...] higher with a scarred uterus  (1 in 14,286 in an unscarred uterus and 1 in 156 in a scarred uterus-source) but my heart told me what I needed to do. I longed for instant bonding with my babe. Not once, but [...]

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