Understanding the Risk of Uterine Rupture
If you’ve had a C-section before, you may have asked your provider about the possibility of giving birth vaginally next time. This is called a vaginal birth after cesarean, or VBAC. Some providers may prefer to call it a TOLAC, or trial of labor after cesarean. Even if your doctor was supportive of the idea, you were probably warned about the risk of uterine rupture, which on the surface sounds pretty scary. This is when the uterus “ruptures” along the previous C-section scar due to the strain of uterine contractions in labor pulling uterine muscle tissue upwards towards to fundus (top of the uterus), and away from the scar tissue around the earlier incision. The reality is that most of the time, the ‘explosion’ implied by the word ‘rupture,’ doesn’t happen at all, and even when a rupture does occur, it is much more likely to result in good outcomes than you’d think, especially when you’re set up in a birth setting with access to quick intervention.
The possibility of rupture is very real, and can potentially result in the death of a mother or baby. But the overstated emphasis on the likelihood of this extreme circumstance happening is called a ‘distortion of risk.’ There have been a number of randomized controlled trials evaluating the actual risk of uterine rupture during an attempted VBAC, and consistently, they result in conclusions that the real risk of uterine rupture for women who go into labor at any gestational age is at 325 in 100,000, or 0.003% according to the NIH, up to even the most conservative estimate being 1 in 200, or .4% (Lyndon), including women with multiple cesarean scars. Those are excellent odds, considering that other types of complications in labor that require immediate cesareans in a normal low risk pregnancy, such as cord prolapse or placental abruption, are just as, or even more, likely to occur in a first-time mom without a scar (Block, 88).
Some particularly dramatic doctors have told women I’ve worked with that the risk of rupture is anywhere from 2-15% of the time, or more. This number commonly gets over-inflated if you’re not familiar with the history of studies on uterine rupture. Older studies from the 1990s and before tended to make no distinction between a uterine rupture and a uterine dehiscence – an asymptomatic separation of the uterine muscle with the outer layer, or serosa, still intact. Some of these studies involved doctor’s doing a cesarean and noticing a ‘window’ or a thinner part of the uterus, and counting that as a rupture, even when there were no symptoms or dangers otherwise. Some of them involved doctors physically examining vbac women internally after a vaginal birth to feel for a dehiscence (ouch!… and why?!). There is just no measurable way to know whether a ‘window’ or ‘dehiscence’ would have, or would ever, result in or lead to a uterine rupture. For all we know, it could either be a sign of a uterine rupture about to happen, or nothing at all. As far as we know, it also does not have any effect on future pregnancies or future vaginal births, especially since we know, uteruses heal.
Some factors might increase or decrease this baseline absolute risk of .4%. Some factors that might influence your particular risk of rupture include:
Previous successful VBAC can decrease your risk
An interdelivery interval of 18 months or less
Multiple previous cesareans
Induction with Cytotec/Misoprostol (a cervical ripening agent) is associated with a dangerous increase in risk, and had not been discovered to be associated with it until more recent studies.
Induction with pitocin can increase the risk slightly, but some may still consider this to be an acceptable risk.
Previous uterine rupture
congenital uterine anomalies
Previous complicated surgery, especially with a T-shaped or a J-shaped scar
If you are a woman considering attempting a VBAC, you have anywhere from a 60 to 95% chance of having a successful vaginal delivery (NIH). But some risk factors have been shown to decrease the likelihood of success for a trial of labor, though there is a possibility that these factors only influence cesarean rates in a labor after cesarean because they influence doctors to preventively or iatrogenically intervene with cesarean:
Continuous fetal monitoring
Gestation or pregnancy going past 40 weeks
suspected big baby
True rupture can be very dangerous, and precautions should be done to protect against its consequences. Some signs of a uterine rupture that your birth attendant might be looking for would include:
Concerning and persistent changes in fetal heart rate (i.e. deviation from normal heart rate patterns that happen consistently)
loss of intrauterine pressure or labor stopping altogether
visible changes in the shape of your abdomen, such as a bandl’s ring, or baby’s presenting parts in the abdomen
decrease in station (the depth of progress the baby has made down the vaginal canal)
Sharp pain that continues even between contractions
Excessive bleeding or hemorrhage
The consequences of rupture can be devastating, especially if it’s compounded with other complications like hemorrhage or blood clotting disorders. But the number of people who suffer long-term consequences from uterine rupture specifically is also commonly overstated. So, here are the numbers:
Perinatal brain damage or death: 130 per 100,000 in a labor after cesarean vs. 50 in a planned repeat cesarean for every 100,000 (NIH). *keep in mind first-time moms’ risk overall is 100 per 100,000 (Macdorman et al.) the absolute risk to your baby’s life in a VBAC is very similar to what it was in your first pregnancy, but is higher than an RCS.
in a labor after cesarean (LAC), Maternal mortality also lessens from 13 down to 4 in 100,000 (NIH).
LAC has a lower risk of hysterectomy (relatively by 7 times: see Goer pg. 285), blood transfusions, and deep-vein thrombosis, and a successful vaginal birth includes a shorter hospital stay.
It’s also clear that among the rare instance of rupture, if immediate action is taken, the risk to the baby’s life is about 6% of the time. Mark Landon, MD, director of maternal-fetal medicine at Ohio State University College of Medicine, says that according to his research, ninety percent of real ruptures actually end well, with a repaired uterus and a healthy mother and child (Block). So as a doula, if you were to ask me, “Are VBACs safe?” I’d say that generally, they are just as safe as a repeat cesarean if not more safe in terms of maternal mortality, and neonatal risks are pretty equivalent to the risks of a first-time birth. But to truly know your personal level of risks, discuss this information with your practitioner, and follow up with your own research. I know and trust that you’ll make the best decision for YOU and your baby.
Block, Jennifer. Pushed The Painful Truth about Childbirth and Modern Maternity Care. Cambridge, MA. 2007
Childbirth Connection, “VBAC or Repeat C-section,” last updated November 16, 2012, http://www.childbirthconnection.org/article.asp?ck=10214.
Zwiefler et al., “Vaginal Birth after Cesarean in California: Before and After a Change in Guidelines,” Annals of Family Medicine 4, no. 3 (2006): 228-34.
Landon, Mark B. et al., “Risk of Uterine Rupture with a Trial of Labor in Women with Multiple and Single Prior Cesarean Delivery,” Obstetrics & Gynecology 108, no.1 (2006): 12-20.
Lydon-Rochelle et al., “Risk of Uterine Rupture During Labor Among Women With a Prior Cesarean Delivery,” New England Journal of Medicine 345, no.1 (2001): 3-8.
Marian F. MacDorman et al., “For Low-Risk Women, Risk of Death May be Higher for Babies Delivered by Cesarean,” Birth 33, no.3 (2006): 175-82.
McMahon et al., “Comparison of a Trial of Labor with an Elective Second Cesarean Section,” New England Journal of Medicine 335 (1996): 689-95.
National Institutes of Health, Consensus Development Statement, “NIH Consensus Development Conference Statement on Vaginal Birth after Cesarean: New Insights,” vol. 27, no. 3 (March 2010), pg. 14 and 17, https://consensus.nih.gov/2010/images/vbac/vbac_statement.pdf.
Simkin, Penny et al. Pregnancy, Childbirth, and the Newborn the Complete Guide. Da Capo Press. New York, NY. Fifth Edition: September 2018.