Applying medical research to clincial realities

Applying medical research to clincial realities

Isabel recently asked over on Uterine rupture rates after 40 weeks:

“I wonder however if there are studies that compare the method of induction. My Doula said that the increase rates of uterine/ scar rupture was due to using high dosages of Pitocin, but now the induction uses lower dosages and administered at longer intervals. Do you know something about this?
Thank you”

Isabel,

Great question.

A few factors to consider:

1. Induction protocols can vary by provider, including some providers who don’t induced planned VBACs at all.
2. Induction guidelines can vary by hospital.
3. Women can react to the same drug/dose differently.
4. Some studies do compare the uterine rupture rates among spontaneous, induced, and augmented planned VBACs.

Medical studies on induction are only relevant to your situation if your provider follows the same protocol outlined in the study. However induction protocols are often not spelled out in detail unless that is the focus of the study.

When reading medical research, make special note of the sample size. We need ample participants in order to accurately capture and report the incidence of uncommon events such as uterine rupture. I typically like to see at least 3,000.

Also remember that it’s ideal to have a experimental group (who receives the induction protocol) and a control group (who does not receive the induction protocol) in order to measure the difference in outcomes, such as fetal distress, uterine rupture, hemorrhage, cesarean hysterectomy, etc. Ideally, we would have a couple thousand, at least, in the experimental and control group.

In terms of the trend that induction now uses lower dosages and is administered at longer intervals, that may be true in some practices, but I would always confirm and not assume.

Anecdotally, I have heard a wide range of induction protocols reported just as research has identified similar variations among cesarean and episiotomy rates that are not linked to medical indication. This California Healthcare Foundation infographic clearly illustrates how hospitals differ:

Tale of Two Births

In terms of specific studies comparing the method of induction, the first resource that comes to mind is the Guise 2010 Evidence Report.

Search for the word Cytotec and there is a discussion comparing rates of rupture by Pitocin, prostaglandins, and Cytotec.

Pitocin is associated with the lowest rate of rupture among the chemical agents which is likely why ACOG (2010) recommends Pitocin and/or Foley catheter induction in planned VBACs when a medical indication presents. (Learn more about what the Pitocin insert actually says.)

There may be more recent studies out there. Google Scholar is a good place to start. You can often obtain the full texts of medical studies at your local library, university, or graduate school.

Also, if you subscribe to Evidence Based Birth’s newsletter, she will email you a crash course on how to find good evidence.

I hope this helps!

Jen

What is the induction protocol at your facility? Does it differ for those with a prior cesarean? Let me know in the comment section.

Resources Cited

American College of Obstetricians and Gynecologists. (2010). Practice Bulletin No. 115: Vaginal Birth After Previous Cesarean Delivery. Obstetrics and Gynecology, 116 (2), 450-463, http://dhmh.maryland.gov/midwives/Documents/ACOG%20VBAC.pdf

California Healthcare Foundation. (2014, Nov). A Tale of Two Births: High- and Low-Performing Hospitals on Maternity Measures in California. Retrieved from California Healthcare Foundation: http://www.chcf.org/publications/2014/11/tale-two-births

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). Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK44571/

Friedman, A. M., Ananth, C. V., Prendergast, E., Alton, M. E., & Wright, J. D. (2015). Variation in and factors associated with use of episiotomy. JAMA, 313(2), 197-199. Retrieved from http://jama.jamanetwork.com/article.aspx?articleid=2089343

Kozhimannil, K. B., Arcaya, M. C., & Subramanian, S. V. (2014). Maternal Clinical Diagnoses and Hospital Variation in the Risk of Cesarean Delivery: Analyses of a National US Hospital Discharge Database. PLoS Med, 11(10). Retrieved from http://journals.plos.org/plosmedicine/article?id=10.1371%2Fjournal.pmed.1001745

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.

Does the term “TOLAC” tweak you?

Does the term “TOLAC” tweak you?

On the acronym TOLAC (trial of labor after cesarean)….

Some studies break out statistics in four ways.

1. ERCS/D (elective repeat cesarean section/ delivery)
2. VBAC (vaginal birth after cesarean)
3. CBAC (cesarean birth after cesarean aka cesarean after planned VBAC)
4. TOLAC (VBAC + CBAC stats)

Because we are unable to predict who will have a VBAC or CBAC, the TOLAC stat enables us to review outcomes from a variety of angles:

  • TOLAC vs. ERCS
  • VBAC vs. ERCS
  • CBAC vs. ERCS

Some women find the TOLAC acronym offensive, because it implies “trying,” so practitioners sensitive to this may way to use the phrase “planning a VBAC.”   Understanding that TOLAC isn’t a dig at moms, but just a straightforward, objective term that care providers use, can (hopefully) take the sting out of the word.

Remember, your care provider is not your girlfriend.  They use clinical terms because that is the language of their world. They speak like clinicians because they are clinicians. All that said, providers who are aware of how the term TOLAC is received by some women use the term “planned VBAC.”

So moms, you use the language that works for you! Just remember that TOLAC is really more of a clinical term and when your provider uses it, it doesn’t necessarily mean that they are a jerk.  They just may have forgotten to code switch from clinical to sensitive language.

Moms don’t typically say, “I’m so excited for my TOLAC!” However, if you do, you might make your provider laugh and connect with them on a human level.

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.

False comparison: Fatal car accidents and VBAC

False comparison: Fatal car accidents and VBAC

RETRACTION/ CORRECTION: I originally posted this article challenging the thought that you are more likely to die in a fatal car accident than during a VBAC.  I tried to crunch the numbers in the way that I felt most accurate.  However, it has been bugging me ever since because there is no accurate way to compare these two events and I should have emphasized that more. We can accurately and fairly compare the risks of VBAC to the risks of a repeat cesarean or the risks of a first time time mom.  However, it is a misleading to compare the risks of birth to non-birth events because they are to different.  While I did discuss this at great length at the end of this article, the title I originally chose (Myth: Mom more likely to die in car accident than VBAC) just continued to feed this false comparison.  I have since updated the article and title.  I apologize for any confusion I caused.

_____________________

On fatal car accident statistics: There are many, many variables that factor into an individual’s risk of dying in a car accident.  The most accurate way to calculate your risk is by miles driven.  To learn more, please refer to the National Motorists Association’s document “Understanding Highway Crash Data.” I use the figures below in order to get an average rate for the purpose of discussion.

On terminology: Read why I use the term TOLAC.

_______________________________

Prepare yourself for yet another installation to the Birth Myth series.  I’ve heard this sentiment many times over the years and I’m sure you have too.   The well-meaning people who share this “statistic” simply desire to give moms seeking information on VBAC some encouragement:

If your husband is worried about you dying during a VBAC, tell him you are four times more likely to die in a car accident on your way home from work today.  Sorry if that sounds morbid, but the odds of the mother dying in a VBAC are truly minuscule.

Another article (filled with inaccurate statements, contradictions, and oodles of statistics without sources) recently making the rounds on Facebook says one of the risks of hospital birth is the 1:10,000 risk of a fatal car accident on the way to the hospital.

While these statements are very comforting, as birth myths tend to be, they are false comparisons.  We can accurately and fairly compare the risks of a TOLAC to the risks of a repeat cesarean or the risks of a first time time.  However, it is a misleading to compare the risks of birth to non-birth events.

Comparing unlike risks

Many birth advocates try to weigh the event of uterine rupture against other life events in an attempt to give context, but this is a misleading and inaccurate comparison.  Andrew Pleasant in his article entitled, Communicating statistics and risk, explains:

Try not to compare unlike risks.  For instance, the all-too-often-used comparison ‘you’re more likely to be hit by a bus / have a road accident than to…’ will generally fail to inform people about the risks they are facing because the situations being compared are so different.  When people assess risks and make decisions, they usually consider how much control they have over the risk.  Driving is a voluntary risk that people feel (correctly or not) that they can control.  This is distinctly different from an invisible contamination of a food product or being bitten by a malaria-carrying mosquito.

Comparing the risk of a non-communicable disease, for example diabetes or heart disease, to a communicable disease like HIV/AIDS or leprosy, is similarly inappropriate.  The mechanisms of the diseases are different, and the varying social and cultural views of each makes the comparison a risky communication strategy.

Take away message: Compare different risks sparingly and with great caution because you cannot control how your audiences will interpret your use of metaphor.

Comparing lifetime/annual risk to your risk of something happening over a day (or two)

Your annual or lifetime risk of something happening will often be higher than your risk of a birth related complication.  But this is because the annual risk of something measures your risk for 365 days.  The lifetime risk of something is often based on 80 years.  You are likely to be in active labor for one day, maybe two.  To compare the risk of something that happens over 1-2 days to the aggregate risk of something that could happen any day over 365 days or 80 years is unfair and confusing.

Look at something like your lifetime risk of breast cancer which is often quoted as 1 in 8.  So one could easily say, “Hey, I have a greater risk of breast cancer over my lifetime than I do have a uterine rupture!”  But, let’s look at this a bit more:

Again, I refer to Andrew Pleasant’s article, Communicating statistics and risk:

An oft-reported estimate is the lifetime breast cancer rate among women. This rate varies around the world from roughly three per cent to over 14 per cent.

In the United States, 12.7 per cent of women will develop breast cancer at some point in their lives. This statistic is often reported as, “one in eight women will get breast cancer”. But many readers will not understand their actual risk from this. For example, over 80 per cent of American women mistakenly believe that one in eight women will be diagnosed with breast cancer each year.

Using the statistic ‘one in eight’ makes a strong headline but can dramatically misrepresent individual breast cancer risk.

Throughout her life, a woman’s actual risk of breast cancer varies for many reasons, and is rarely ever actually one in eight. For instance, in the United States 0.43 per cent of women aged 30–39 (1 in 233) are diagnosed with breast cancer. In women aged 60–69, the rate is 3.65 per cent (1 in 27).

Journalists may report only the aggregate lifetime risk of one in eight because they are short of space. But such reporting incorrectly assumes that readers are uninterested in, or can’t comprehend, the underlying statistics. It is critically important to find a way, through words or graphics, to report as complete a picture as possible.

Take away message: Be extra careful to ensure your readers understand that a general population estimate of risk, exposure or probability may not accurately describe individual situations. Also, provide the important information that explains variation in individual risk. This might include age, diet, literacy level, location, education level, income, race and ethnicity, and a host of other genetic and lifestyle factors.

To compare events that are so different like the risk of a fatal car accident and the risk of TOL maternal mortality is inaccurate and doesn’t help moms understand their options.  Your risk of a car accident depends on how much you drive, when you drive, if you are distracted or on medication, etc, etc, etc.  The variables that impact your risk of dying during a  TOLAC are very different.  However, one way these two events are similar:  Sometimes we can make all the “right” or “wrong” decisions and the element of luck will sway us towards a good or bad outcome.

The problems with birth myths and false comparisons

False comparisons and birth myths like this are shared with the best of intentions.  So often the risks of VBAC are exaggerated for reasons having nothing to do with the health of baby and mom.  Birth advocates share these myths (which they believe to be true) as a way of boosting the morale of moms seeking VBAC as these moms are constantly faced with a barrage of unsupportive comments from family, friends, and even care providers.

The problem is, women make plans to have (home) VBAC/VBAMC based on these myths.  They make these plans because birth myths make the risk of VBAC, uterine rupture, infant death, and maternal death look practically non-existent.  That is dangerous.

Perpetuating these myths impedes a mom’s ability to provide true informed consent.  If a mom thinks her risk of uterine rupture is similar to a unscarred mom or a unscarred, induced mom, or less than her risk of getting struck by lighting or bitten by a shark, she does not have accurate picture of the risk.  And if she doesn’t understand the risks and benefits of her options, she is unable to give informed consent or make an informed decision.

Birth advocates get all up in arms about the mom who plans an elective, primary cesarean section without “doing her research.”  Or the mom who consents to an induction at 38 weeks because her OB “said it was for the best.”  Or when an OB coerces a mom into a repeat cesarean by saying the risk of uterine rupture is 15%.  Shouldn’t we be just as frustrated when moms plan (home) VBACs based on misrepresentations of the truth?  Shouldn’t we hold ourselves to the same standard that we expect from others?

The second problem with perpetuating these false comparisons and myths is that once women learn the true risks, they seem gigantic in comparison to the minuscule risk they had once accepted.  Now VBAC seems excessively risky and some loose confidence in their birth plans.  Birth advocates do not support moms by knowingly perpetuating these myths.  The reality is, the risks of VBAC are low.  We don’t need to exaggerate or minimize the benefits or risks of VBAC.  If we just provided women with accurate information from the get go, they would be able to make a true, informed decision.

The third problem is that we really look dumb when we say stuff like this.  If we want to be taken seriously, we really need to double check what we pass on.  I encourage you to ask for a source when someone says something that sounds to good to be true or just plain fishy.  (And hold me to the same standard!)  I often ask people for a source for their assertions… with varying results.

Sometimes people have a credible source available and share it with me.  I learn more and it’s all good.  Other times, people get angry.  They think I’m challenging them or trying to argue with them.  But the truth is, I’m just trying to learn. What I have found is, when people get angry, it’s sometimes because they don’t have a source and they are insulted that I didn’t accept their statement at face value.  They have just accepted what a trusted person told them as the truth and expect me to do the same.

Doesn’t it strike you as odd that some people encourage the continual questioning OBs and the medical system, yet expect you to accept what they say as The Truth no questions asked?   “Question everyone but me.”  Why?  Why is it when we question an OB, that’s a good thing, yet when we hold our birthy friends and colleagues to the same standard, that is being argumentative?  I say, ask for the source.  From everyone.

Take away messages

It is inaccurate and misleading to compare two events that are as different as a fatal car accident and TOL maternal mortality.  Period.

Let’s stop this false comparison and bring us back to what we should be comparing TOLAC/VBAC to: the risks of a repeat cesarean.

When women plan a VBAC based on false information,  their confidence can be shattered when they learn that the risk of uterine rupture and maternal death are much higher than they were lead to believe.

When women plan a VBAC based on false information, they are deprived of their right to informed consent.

While the risk of scar rupture is very different than the risk of a fatal car accident, it is similar to other serious obstetrical emergencies such as placental abruption, cord prolapse, and postpartum hemorrhage.

Guise J-M, Eden K, Emeis C, Denman MA, Marshall N, Fu R, Janik R, Nygren P, Walker M, McDonagh M. Vaginal Birth After Cesarean: New Insights. Evidence Report/Technology Assessment No.191. (Prepared by the Oregon Health & Science University Evidence-based Practice Center under Contract No. 290-2007-10057-I). AHRQ Publication No. 10-E003. Rockville, MD: Agency for Healthcare Research and Quality. March 2010.   http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf

_________________________________

For those who are interested in the reasoning and mathematics from the original article:

But, if we were going to compare the unlike risks of a fatal car accident and TOLAC, this is how I would do it: compare the daily risks of the events.

Maternal death and TOL

Per the report presented at the 2010 NIH VBAC conference entitled Vaginal Birth After Cesarean: New Insights (Guise, 2010):

Overall rates of maternal harms were low for both TOL [trial of labor] and ERCD [elective repeat cesarean delivery]. While rare for both TOL and ERCD, maternal mortality was significantly increased for ERCD at 13.4 per 100,000 versus 3.8 per 100,000 for TOL . . . The rate of uterine rupture for all women with prior cesarean is 3 per 1,000 and the risk was significantly increased with TOL (4.7/1,000 versus 0.3/1,000 ERCD).

Put another way, there is a 0.0038% (1 in 26,316) risk of maternal death during a trial of labor.  For a mom to die is very rare.

Risk of a fatal car accident

Of the 311,000,000 people living in the US (US Census, 2012), about 40,000 die annually (Beck, 2006) from car accidents in the United States which gives us a annual rate of 0.0129% (1 in 7,752).  (But remember, this is a very rough representation of the risk due to all the factors I previously mentioned.)

Many women look at this number and say, “See, you are more likely to die in a car accident than during a TOL.”

But remember, 0.0129% (1 in 7,752) is the annual rate of Americans dying due to car accidents.

To compare something like your annual risk of a fatal car accident to your risk of dying during a TOL is an unfair and inaccurate comparison.   It would be more accurate (though still a false comparison) to compare your daily risk of a fatal car accident (because most people travel in a car every day) to the risk of maternal death during a TOL because you are not in labor every day for a year.  Let me explain.

Comparing TOL maternal mortality to fatal car accidents

Often this false comparison is expressed as, “You are more likely to have a fatal car accident on the way to the hospital than have a uterine rupture or die during a VBAC.”  But the risk of a fatal car accident on the day you drive to the hospital is not 1 in 7,752.  That is your risk over a year.  We have to estimate your risk on that day you drive to the hospital by dividing 0.0129% by 365 days which equals 0.00003534% or 1 in 2,829,458.

No matter what stat we use from any study, the risk of maternal mortality during a TOL is much greater.  (But remember, this is a false comparison anyways!)

Guise’s data pegs the risk at 0.0038% or 1 in 26,316 which is 107.5 times greater than the risk of a fatal car accident as you drive to the hospital in labor.  This does not mean that the risk of dying during a TOL is so large, but rather our daily risk of a fatal car accident is so small that it’s literally theoretical.  (Read Kim James’ “Understanding obstetrical risk” for more.)

What about the risk of uterine rupture?

Using the 0.47% (1 in 213 TOLs) risk of scar rupture (Guise, 2010), the risk of a fatal car accident is 13,283 times smaller.

Why don’t we spread the risk of rupture/maternal mortality across the entire pregnancy?

After I initially published this article, someone left this great comment on Facebook:

I get this, but I also get why using annual stats of car accidents would be accurate when you are looking at uterine rupture rates themselves and not just during TOL, since a risk of rupture exists throughout pregnancy and not just during labor and mom would be pregnant for approximately 10 months or more.

I wondered about the best way to crunch the numbers because these events are so different and thus so difficult to compare.  In the end, it is a false comparison, but here was my original thinking….

Most Americans are in a car everyday, so they have that risk – no matter how small – every day unless they are not in a car in which case their risk is zero.  The risk is primarily associated with being in a car.

The risk of uterine rupture and maternal mortality is primarily associated with being in labor, so we can’t spread the risk of rupture/maternal mortality across the whole pregnancy because the risk of rupture/maternal mortality is not the same from conception to delivery.

One study examined 97% of births that occurred in the The Netherlands from 1st August 2004 until 1st August 2006 and found that 9% (1 in 11) of scar ruptures happened before the onset of labor. When we take 9% of the overall rate of scar rupture 0.64% (1 in 156) (including non-induced/augmented, induced, and augmented labors), we get a 0.0576% (1 in 1736) risk of pre-labor scar rupture and a 0.5824% (1 in 172) risk of rupture during labor (Zwart 1009). Since the risk of rupture is not the same over the entire pregnancy and labor, we cannot accurately calculate a daily risk of rupture.

In other words, the risk of rupture is rare before labor (0.0576% or 1 in 1736) and then becomes uncommon when labor begins (0.5824% or 1 in 172).  Even though we could go into labor anytime during pregnancy, the risk before we go into labor is so small in comparison to the risk when we actually go into labor.

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.

Myth: Two numbers less than 1% are similar

Myth: Two numbers less than 1% are similar

I have often heard, “If two numbers are less than 1%, they are similar.”  Typically
this is expressed while comparing the risks of rupture in an unscarred versus scarred uterus.   But is this true?  How different can two numbers less than 1% be?

Two numbers less than 1% are no more similar than two numbers greater than 1%

Just because two numbers are less than 1%, that doesn’t make them any more similar than two numbers greater than 1%.  A 2% risk of something happening is very different than an 89% risk.  While they are both greater than 1%, they represent drastically different levels of risk.

2% = 1 in 50 risk

89% = 1 in 1.12 risk

89% represents a 44 times greater risk than 2%.

What about numbers less than 1%?

It might seem rational that since numbers less than 1% are so small, that there wouldn’t be as much of a difference between them.  But numbers less than 1% work in the same way as those greater than 1%.   Let’s run a few and measure the difference.

1 in 100 represents 1%.

1 in 1,000, is the same as 0.1%, and is 10 times smaller than 1%.

1 in 10,000, is the same as 0.01%, and is 100 times smaller than 1%.

1 in 100,000, is the same as 0.001%, and is 1,000 times smaller than 1%.

1 in 1,000,000, is the same as 0.0001%, and is 10,000 times smaller than 1%.

Comparing small risks

According to Zwart* (2009), the risk of uterine rupture in:

– an unscarred mom is 1 in 14,286 (0.007% or 0.7 in 10,000) and

– a scarred mom is 1 in 156 (0.64% or 64 in 10,000).

(Both statistics include non-induced/augmented, induced, and augmented labors.)  Even though both numbers are less than zero, they represent very different levels of risk.  In fact, the risk of rupture in an unscarred mom is 91 times smaller than a scarred mom.  It’s not that the risk of rupture is excessively high in a scarred mom, but that it is so very, very, very low in an unscarred mom.

Using the language from Kim James’ handout Understanding Obstetrical Risk, the risk of rupture in an unscarred mom would be described as “very rare” whereas the risk of rupture in a scarred mom would be described as “uncommon.”

Take away messages

Just because two numbers are less than 1% does not mean that they are similar.  Numbers below 1% represent just as much of a range as numbers greater than 1%.

While the risk of scar rupture is very different than the risk of unscarred rupture, it is similar to other serious obstetrical emergencies such as placental abruption, cord prolapse, and postpartum hemorrhage.

Resources Cited

* Zwart (2009) differentiated between uterine rupture and dehiscence, featured 358,874 total deliveries, 25,989 of which were trials of labor after a cesarean.  Zwart included 97% of births in The Netherlands between August 1, 2004 and August 1, 2006, making it “the largest prospective report of uterine rupture in women without a previous cesarean in a Western country.”

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

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.

The best compilation of VBAC/ERCS research to date

The best compilation of VBAC/ERCS research to date

“There is a major misperception that TOLAC [trial of labor after cesarean] is extremely risky” – Mona Lydon-Rochelle PhD, MPH, MS, CNM, March 2010

In terms of VBAC, “your risk is really, really quite low” – George Macones MD, MSCE, March 2010

Both Drs. Macones and Lyndon-Rochelle are medical professionals and researchers who made these statements at the 2010 NIH [National Institutes of Health] VBAC Conference. Now you may think, “Wait a sec. Everything I’ve heard from my family, friends, and medical provider is how risky VBAC is and how cesareans are the conservative, prudent, and safest choice.” Why the discrepancy between the statements of these two prominent care provider researchers and the conventional wisdom prevalent in America?

It’s likely that your family, friends, and even your medical provider are not familiar with the latest and best compilation of VBAC research that was released in March 2010. It’s also possible that they are not familiar with the latest VBAC recommendations published in July 2010 by the American Congress of Obstetricians and Gynecologists (ACOG). Additionally, there are often legal and non-medical factors at play that influence how care providers counsel women on VBAC, including pressure from hospital administrators.

When I come across any VBAC study, I always wonder if it made the cut to be included in the 400 page Guise 2010 Evidence Report that was the basis for the 2010 NIH VBAC Conference. Guise 2010 reviewed each published VBAC study, performed a quality assessment, and assembled an excellent review of the VBAC literature to date:

Quality assessment is an assessment of a study’s internal validity (the study’s ability to measure what it intends to measure). If a study is not conducted properly, the results that they produce are unlikely to represent the truth and thus are worthless (the old adage garbage in garbage out). If however, a study is structurally and analytically sound, then the results are valuable. A systematic review, is intended to evaluate the entire literature and distill those studies which are of the highest possible quality and therefore likely to be sound and defensible to affect practice.

Guise focused on these key questions: “1) a chain of evidence about factors that may influence VBAC, 2) maternal and infant benefits and harms of attempting a VBAC versus an elective repeat cesarean delivery (ERCD), and 3) factors that may influence maternal and infant outcomes.” Ultimately, this 400 page document was distilled into the 48 page VBAC Final Statement produced by the NIH VBAC Conference.

This is wonderful because people who want the big picture, can read the VBAC Final Statement whereas those who want to know the exact figures, how studies were included/excluded, and the strength of the data available, can read the Guise 2010 Evidence Report.

You can get a feel for the topics presented at the NIH VBAC Conference by reading the Programs & Abstracts document. If you want more detail, you can watch the individual presentations. I was there for the three day conference and it was eye opening. I wish more medical professionals and moms were aware of this information as they are excellent resources for anyone looking to learn more about VBAC.

Everyone wants to know the bottom line: what is the risk of death or major injury to mom and baby. Here is an overview of maternal and infant mortality and morbidity per Guise (2010). It’s important to remember that the quality of data relating to perinatal mortality was low to moderate due to the high range of rates reported by the strongest studies conducted thus far. Guise reports the high end of the range when they discuss perinatal mortality which was 6% for all gestational ages and 2.8% when limited to term studies. This is a long way of saying, we still don’t have a good picture of how many babies die due to uterine rupture.

It’s also important to remember that the statistics shared in Guise (2010) are for all VBACs. They include all scar types, women who have had multiple prior cesareans, induced/augmented labors, etc. It would have been helpful if they had broke out the data in these ways as we know we can reduce the risk of rupture (and thus perinatal mortality) through spontaneous labor.

While rare for both TOL [trial of labor after cesarean] and ERCD [elective repeat cesarean delivery], maternal mortality was significantly increased for ERCD at 13.4 per 100,000 versus 3.8 per 100,000 for TOL. The rates of maternal hysterectomy, hemorrhage, and transfusions did not differ significantly between TOL and ERCD. The rate of uterine rupture for all women with prior cesarean is 3 per 1,000 and the risk was significantly increased with TOL (4.7 1,000 versus 0.3 1,000 ERCD). Six percent of uterine ruptures were associated with perinatal death. Perinatal mortality was significantly increased for TOL at 1.3 per 1,000 versus 0.5 per 1,000 for ERCD… 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 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. While TOL rates have decreased over the last decade, VBAC rates and adverse outcomes have not changed suggesting that the reduction is not reflecting improved patient selection.

Women are entitled to accurate, honest, and high quality data. They don’t deserve to have the risks exaggerated by an OB who wishes to coerce them into a repeat cesarean nor do they deserve to have risks sugar-coated or minimized by a midwife or birth advocate who may not understand the risk or whose zealous desire for everyone to VBAC clouds their judgement. Sometimes it can be hard to find good data on VBAC which is why I’m so thankful for the 2010 NIH VBAC Conference and all the excellent data that became available to the public as a result. There are real risks and benefits to VBAC and repeat cesarean and once women have access to good data, they can individually choose which set of risks and benefits they want. I think the links I have provided above represents the best data we have to date.

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.

Confusing fact: Only 6% of uterine ruptures are catastrophic

Confusing fact: Only 6% of uterine ruptures are catastrophic

It is important to note that the information shared in Guise (2010), the 400 page Evidence Report on which the 2010 NIH VBAC Conference was based, collected the best data we have available on trial of labor after cesarean.  That said, they reported, “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.  Bottom line: We still don’t have an accurate idea of how deadly uterine rupture is to babies.  This is a topic on which Guise recommended future researchers focus.  I highly recommend that anyone interested in TOLAC (trial of labor after cesarean), especially those who blog or share information on social networking sites, review this very important document as it is a fascinating analysis of the best research we have to date on TOLAC.


How many times have you heard, “Only 6% of uterine ruptures are catastrophic” or “Uterine rupture not only happens less that one percent of the time, but the vast majority of ruptures are non-catastrophic?” But what does that mean? Does that mean only 6% of uterine ruptures are “complete” ruptures? Result in maternal death? Infant death? Serious injury to mom or baby? This article will explain to you the difference between uterine rupture and uterine dehiscence as well as explain the source and meaning of the 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, also called true, complete, or even (to further add to the confusion) catastrophic rupture, is a opening through all the layers of the uterus. Per a Medscape article on Uterine Rupture in Pregnancy:

Uterine rupture is defined as a full-thickness separation of the uterine wall and the overlying serosa. Uterine rupture is associated with (1) clinically significant uterine bleeding; (2) fetal distress; (3) expulsion or protrusion of the fetus, placenta, or both into the abdominal cavity; and (4) the need for prompt cesarean delivery and uterine repair or hysterectomy.

Whereas a uterine dehiscence, also called a incomplete rupture or a uterine window, is not a full-thickness separation. It’s often asymptomatic, does not pose any risk to mom or baby, and does not require repair. Again, I refer to Medscape:

Uterine scar dehiscence is a more common event that seldom results in major maternal or fetal complications. By definition, uterine scar dehiscence constitutes separation of a preexisting scar that does not disrupt the overlying visceral peritoneum (uterine serosa) and that does not significantly bleed from its edges. In addition, the fetus, placenta, and umbilical cord must be contained within the uterine cavity, without a need for cesarean delivery due to fetal distress.

When reading medical studies, look for how they define uterine rupture in the “Methods” section. While some medical studies combine the statistics for rupture and dehiscence, ultimately reporting an inflated rate of rupture, other studies distinguish between the two events.

So, what does the 6% statistic mean and where did it come from?

The statistic “Only 6% of uterine ruptures are catastrophic” is from the Evidence Report (Guise 2010) which was the basis of the 2010 NIH VBAC Conference and it refers to the rate of infant death due to uterine rupture. 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 (Guise 2010).

In other words, of the women who had uterine ruptures, 6.2% (1 in 16) resulted in infant deaths. When we limited the data to women delivering at term, as opposed to babies of all gestational ages, the risk was as high as 2.8 (1 in 36)%.

When we look at the overall risk of an infant death during a trial of labor after cesarean, the NIH reported the rate of 0.13%, which works out to be one infant death per 769 trials of labor.

The source of the confusion

The problem with this statistic is that some people have misinterpreted it to mean that only 6% of ruptures are true, complete uterine ruptures. In other words, if we take the 0.4% (1 in 240) uterine rupture rate (Landon, 2004), they believe that only 6% of those ruptures or 0.024% (1 in 4166) are true, complete ruptures. This is false. The 0.4% uterine rupture statistic measured true, complete, uterine ruptures in spontaneous labors after one prior low, transverse (“bikini cut”) cesarean.

So how many dehiscences did Landon (2004) detect? Landon reported a 0.7% uterine rupture rate and a 0.7% dehiscence rate. (Note that these statistics include a variety of scar types as well spontaneous, augmented, and induced labors.) So Landon found that dehiscence occurs at the same rate as uterine rupture.

I think the best way to avoid confusion is to use very clear language: 6.2% (1 in 16) of uterine ruptures result in an infant death. Put another way, for every 16 uterine ruptures, there will be one baby that dies.

Elapsed time and infant death

What determines if a baby dies or has brain damage? Some research on infant cord blood gases has suggested that if the baby isn’t delivered (almost always by CS) within 16 – 17 minutes of a uterine rupture, there can be serious brain damage or death to baby. You can watch a presentation from the 2010 NIH VBAC Conference entitled “The Immediately Available Physician Standard” by Howard Minkoff, M.D. for more information or read his presentation abstract.

Now you know the difference between uterine rupture, uterine dehiscence and the meaning of the 6% statistic. It’s helpful to understand the terminology used in relation to uterine rupture otherwise it can be very confusing as you wade your way through the statistics! It’s also very important for people to use specific words whose definitions are clear instead of words such as “catastrophic” that could mean multiple things.

Afterward – The big picture

The following are excerpts from the Evidence Report (Guise 2010) , the 400 page evidence report assembled for the 2010 NIH VBAC Conference. The limitation of Guise (2010) is that these stats are for all VBACs – all scar types, multiple prior cesareans, induced/augmented labors, etc. It would have been helpful if they had broke out the data in these ways.

While rare for both TOL [trial of labor] and ERCD [elective repeat cesarean delivery], maternal mortality was significantly increased for ERCD at 13.4 per 100,000 versus 3.8 per 100,000 for TOL. The rates of maternal hysterectomy, hemorrhage, and transfusions did not differ significantly between TOL and ERCD. The rate of uterine rupture for all women with prior cesarean is 3 per 1,000 and the risk was significantly increased with TOL (4.7 1,000 versus 0.3 1,000 ERCD). Six percent of uterine ruptures were associated with perinatal death.” Perinatal death due to UR from term studies was 2.8%. “Perinatal mortality was significantly increased for TOL at 1.3 per 1,000 versus 0.5 per 1,000 for ERCD… 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 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. While TOL rates have decreased over the last decade, VBAC rates and adverse outcomes have not changed suggesting that the reduction is not reflecting improved patient selection.

A systematic review strives to be patient-centered and to provide both patients and clinicians with meaningful numbers or estimates so they can make informed decisions. 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 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 Taken in aggregate, the evidence suggests that the approximate risks and benefits that would be expected for a hypothetical group of 100,000 women at term gestational age (GA) who plan VBAC rather than ERCD include: 10 fewer maternal deaths, 650 additional uterine ruptures, and 50 additional neonatal deaths. Additionally, it is important to consider the morbidity in future pregnancies that would be averted from multiple cesareans particularly in association with placental abnormalities.

What do you think? Leave a comment.

Jen Kamel

Jen Kamel is the founder of VBAC Facts, an educational, training and consulting firm. As a nationally recognized VBAC strategist and consumer advocate, she has been invited to present Grand Rounds at hospitals, served as an expert witness in a legal proceeding, and has traveled the country educating hundreds of professionals and highly motivated parents. She speaks at national conferences and has worked as a legislative consultant in various states focusing on midwifery legislation and regulations. She has testified multiple times in front of the California Medical Board and legislative committees on the importance of VBAC access and is a board member for the California Association of Midwives.

Learn more >

Free Report Reveals...

Parents pregnant after a cesarean face so much misinformation about VBAC. As a result, many who are good VBAC candidates are coerced into repeat cesareans. This free report provides quick clarity on 5 uterine rupture myths so you can tell fact from fiction and avoid the bait & switch.

VBAC Facts does not provide any medical advice and the information provided should not be so construed or used. Nothing provided by VBAC Facts is intended to replace the services of a qualified physician or midwife or to be a substitute for medical advice of a qualified physician or midwife. You should not rely on anything provided by VBAC Facts and you should consult a qualified health care professional in all matters relating to your health.