1/18/12 – The difference in uterine rupture (UR) rates between unscarred and scarred uteri is significant: 0.7 in 10,000 in an unscarred uterus and 64 in 10,000 in a scarred uterus. This 91% increase in 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.
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
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.
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.
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
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
Jessica W.
I’m so sorry your OB wasn’t supportive of VBAC, but your repeat CS might have been necessary due to your gestational diabetes. The best way to know is to get a copy of your medical records and operative report for both surgeries and schedule some consultations with 2-3 VBAC supportive care providers to get their opinions. You might have to meet with more in order to find someone truly supportive. Here is a list of questions to ask them (http://vbacfacts.com/2009/06/06/interviewing-care-providers-questions-to-ask/) and ways to find them (http://vbacfacts.com/2008/03/08/finding-a-vbac-supportive-ob-or-midwife/). Just be aware that there are a lot of OBs out there who say they are supportive of VBAC, but really aren’t (http://vbacfacts.com/2008/04/13/the-three-types-of-care-providers-amongst-obs-and-midwives/), so getting referrals from women who have successfully VBACed is a good way to find a VBAC OB.
Read more on planning a VBAC here: http://vbacfacts.com/2009/01/15/im-pregnant-and-want-a-vbac-what-do-i-do/.
In terms of birth intervals, we really need larger studies to give us some definitive evidence. Read more here: http://vbacfacts.com/2011/11/11/birth-intervals-uterine-rupture/.
If you want to read the research available on VBAC after multiple cesareans (VBAMC), go here: http://www.plus-size-pregnancy.org/CSANDVBAC/csvbacindex.html#VBAC%20After%20Multiple%20Cesareans%20FAQs
Best of luck!
Jen