We have previously discussed the problematic studies behind the 4-9% uterine rupture statistic associated with vaginal birth after a classical or T/J cesarean. Given the limited data available on these scar types, how should people who have had these types of cesareans, and want a VBAC, be counseled?

The challenge with 4-12% classical incision uterine rupture rates

First and foremost, I think we need to be honest and clearly communicate what we know and what we don’t. Conventional wisdom states that the uterine rupture risk is 4-9% or even 12%. However there are many problems with how the studies behind these statistics were conducted. As a result, we cannot say that these numbers accurately represent the risk.

However there are many problems with how the studies behind these statistics were conducted.

Notably, those studies were very small and their reported uterine rupture rates include uterine dehiscences, a benign, asymptomatic event where the uterine muscle separates, but the outer uterine layer stays intact. We need to be clear that the 9% classical cesarean uterine rupture rate not only included dehiscences but was calculated based on only those who had a vaginal delivery, rather than including all who labored after a cesarean which would have brought the rate down to 4.7%.

We need to share that modern studies on vaginal birth after classical cesarean, including T/J incisions, are few and far between because most people with these scar types have a repeat cesarean in the absence of labor. Additionally, the largest studies we have are from the mid 1900s when uterine rupture and uterine dehiscence were routinely grouped together resulting in an inflated reported rate of uterine rupture. This makes it very difficult for us to state where the risk lies with any confidence.

Why Landon’s 2004 study is not the answer to vaginal birth after classical incision uterine rupture rates

Many people point to Landon’s 2004 study which included 105 people who had a VBAC after a classical or T/J incision. However, it’s important to stress that this is an incredibly small sample size and so it’s not entirely accurate to claim that the risk is really only 1.9%. 

We cannot honestly say that risk of uterine rupture during a VBAC after a classical or T/J cesarean is only 1.9%.

In order to make that determination, we would need several sizable studies that came to a similar conclusion which we simply do not have. This study represents a single data point, not the answer to the question. 

Even though it is the largest group of people with a classical or T/J incision who planned a VBAC in a modern study, it is still a very small group. We cannot honestly say that risk of uterine rupture during a VBAC after a classical or T/J incision is only 1.9%. The risk remains unknown. This is important for birthing women and people to hear.

The largest study on VBAC after classical cesarean

The largest study we were able to uncover on vaginal birth after classical cesarean was published by Eames in 1953 and detailed in a 2005 historical review by de Costa. Of 902 vaginal births after classical cesarean, there were 23 ruptures, for a rate of 2.6%. Compare that with the 880 vaginal births after a lower uterine cesarean where 11 ruptures occurred for a rate of 1.3%. 

The largest study we were able to uncover on vaginal birth after classical cesarean was published by Eames in 1953.

Remember that these numbers very likely include dehiscences so the true occurrence of uterine rupture is probably significantly lower. I also wonder about induction or augmentation. No mention is made. 

De Costa’s review itemizes a handful of other studies on vaginal birth after classical cesarean from that time period. These include a 1948 study by Hindman of 104 people who labored after one classical cesarean and another four who either had two prior classical cesareans or one classical and one lower uterine cesarean. He reported a uterine rupture range of 1.5 – 6%. Then a 1951 study by Browne which included 8 classical VBACs, no ruptures and a 1953 study by Lane and Reid including 91 vaginal births after classical cesarean where one ruptured during labor and two ruptured late in pregnancy.

What about modern studies on VBAC after classical or inverted T/J cesarean?

What have modern studies reported? As virtually everyone with a classical or T/J incision has a repeat cesarean in subsequent pregnancies, sizeable studies on vaginal birth after classical or T/J incisions is hard to find. 

A 2002 study by Patterson followed the outcomes of 45 people with classical incisions who had 61 subsequent deliveries, 53 of which were elective repeat cesareans. Among the 8 who labored, 5 delivered via a low transverse incision, two had an emergency cesarean, and one had a vaginal delivery. There was one uterine rupture and one dehiscence presumably among those who labored, but the authors are not clear.

Patterson also followed the outcomes of 17 people who had an inverted T incision. Among them were 18 deliveries, 14 of which were elective repeat cesareans. Of the four people who labored, two had a vaginal delivery. These are really small numbers. 

Of the four people who labored, two had a vaginal delivery.

Another study by Chauhan in 2002 included data on 157 people who had another delivery after a classical cesarean. While it was their protocol for all people to have an elective cesarean at 36 weeks after lung maturity was assessed via amniocentesis, half of these people actually labored. So what happened during those 77 labors?

I was surprised to learn that the average labor length among these people was 7.3 hours plus or minus 5.6 hours. It does not seem that these physicians back in 2002 were that worried about these people laboring even though they all had repeat cesareans eventually. 

17% reached or surpassed 4 centimeters by the time of their surgical delivery, the threshold for active labor at the time, and the average dilation at surgical delivery was only 1.5 centimeters plus or minus 2.4 centimeters.

So as we had 157 people with a prior classical cesarean, 77 of which labored for about 7 hours, how many uterine ruptures do you think occurred?

So what were the outcomes among these 157 people? 15, representing 9%, experienced asymptomatic dehiscence. When the researchers looked to see if there were any differences between the people who did and did not have a dehiscence, they couldn’t find any. So as we had 157 people with a prior classical cesarean, 77 of which labored for about 7 hours, how many uterine ruptures do you think occurred?

The researchers reported one and it wasn’t among those 77 people who labored. It was among someone who had a uterine rupture at 29 weeks gestation. They presented at the hospital with vaginal bleeding and a crash cesarean was performed 14 minutes after the onset of fetal bradycardia (abnormally slow heart beat). The placenta had prematurely separated from the uterus and had been expelled into the abdomen along with the fetus through what they called a 6cm vertical “uterine defect.” The newborn was not able to be resuscitated. This was the only perinatal mortality in the study. 

Ultimately, there was not one uterine rupture among those 77 people who labored. So what does this mean? Not much. Again, this is a really small group of people who did not reach second stage, but, this is the type of data we have available to us as we try to piece together the risk of uterine rupture during a vaginal birth after a classical cesarean. Chauhan is clear to point out that a policy of repeat cesarean at 36 weeks would not have prevented the one uterine rupture and perinatal mortality in this study as it occurred well before term.

What else do parents need to know about VBAC after classical or T/J incision?

Given the limited data, what else do parents interested in a VBAC after classical or T/J incision need to know? We need to explain that while conventional wisdom believes that the fundus “does all the work in labor,” we have a 2005 study showing that there is no difference between the contractility of the lower and upper myometrium (uterine muscle). (Luckas & Wray, 2005) (Efforts to find other studies on this topic were fruitless, so if you know of any, please leave a comment below or contact me.)

We need to be clear, as Chauhan said in 2002, “Among patients with prior classic cesarean delivery, uterine rupture and dehiscence are neither predictable nor preventable” and that the outcome could result in a fetal demise. 

People need to know that the often cited 6.2% risk of catastrophic rupture, meaning a uterine rupture that results in a fetal demise, reported by the National Institutes of Health, is based on low transverse scars. We don’t know if this rate is applicable to classical or T/J scars. As Landon 2011 says, “further, it is unknown whether the maternal and fetal risks associated with uterine rupture of the classical scar are appreciably different from these associated with previous low transverse rupture in labor.”

As Landon 2011 clarified for us, “this approach has been undertaken despite little to no information concerning the risk of uterine rupture between 36 and 39 weeks’ gestation.” 

The risk of prelabor rupture seems greater with classical incisions but again, some of those studies are quite old. Some had very small sample sizes, and some categorized dehiscences as uterine ruptures. Based on the practices of that time, we also have to ask, if someone makes it to term, does that mean their scar has already been tested as de Costa suggests? 

We need to explain that ACOG recommends those with a prior classical incision deliver subsequent pregnancies between 36 weeks and zero days and 38 weeks and 6 days via elective repeat cesarean. However, this is based on the belief that the risk of uterine rupture after a classical cesarean is many times higher than the risk associated with prior low transverse incisions which has not been established. As Landon 2011 clarified for us, “this approach has been undertaken despite little to no information concerning the risk of uterine rupture between 36 and 39 weeks’ gestation.” 

VBAC after classical cesarean and patient autonomy

We have a responsibility to inform birthing people that even though ACOG makes this recommendation about early delivery via repeat cesarean, they also stress that care needs to be “individualized based on the clinical situation.” 

ACOG (2019) is clear that “the patient and her obstetrician or other obstetric care provider may judge it best to proceed with TOLAC [trial of labor after cesarean].”

They give an example: if someone presents at the hospital in active labor who might otherwise not be considered a VBAC candidate, what should happen? ACOG (2019) is clear that “the patient and her obstetrician or other obstetric care provider may judge it best to proceed with TOLAC [trial of labor after cesarean].”

As Landon experienced in his 2004 study, there will be people with classical or T/J scars who want to VBAC and will decline a cesarean. These decisions need to be honored because as de Costa reminds us, many of these people will have a VBAC with no complications. Further, as ACOG (2016) has affirmed many times for decades, the ultimate decision on how to birth lies with the birthing woman or person.

Want to learn more about this topic? We dive into all the details in our continuing education training, “Decoding Classical, T/J, and Low Vertical Scars: Navigating Limited Knowledge and Unknown Risk” available through VBAC Facts® Professional Membership.

Jen

Resources Cited

American College of Obstetricians and Gynecologists. (2016). Refusal of medically recommended treatment during pregnancy. Committee Opinion No. 664. Obstetrics & Gynecology, 127, e175-82. http://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Ethics/Refusal-of-Medically-Recommended-Treatment-During-Pregnancy

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

Browne, O. (1951). A summary of 100 deliveries in the Rotunda Hospital following previous Caesarean section. The Journal of Obstetrics and Gynaecology of the British Empire, 58, 555-557.

Chauhan, S. P., Magann, E. F., Wiggs, C. D., Barrilleaux, P. S., & Martin, J. N. (2002). Pregnancy after classical cesarean delivery. Obstetrics & Gynecology, 100(5), 946-950. https://doi.org/10.1016/s0029-7844(02)02239-1

De Costa, C. (2005). Vaginal birth after classical Caesarean section. Australian and New Zealand Journal of Obstetrics and Gynaecology, 45, 182-186. https://doi.org/10.1111/j.1479-828X.2005.00387.x

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

Hindman, D. H. (1948). Pelvic delivery following Caesarean section. American Journal of Obstetrics and Gynecology, 55, 273-285.

Landon, M. B., & Lynch, C. D. (2011). Optimal timing and mode of delivery after cesarean with previous classical incision or myomectomy: a review of the data. Seminars in Perinatology, 35(5), 257-261. https://doi.org/10.1053/j.semperi.2011.05.008

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

Lane, F. R., & Reid, D. E. (1953). Dehiscence of previous uterine incision at repeat Caesarean section. Obstetrics & Gynecology, 2, 54-62.

Luckas, M. J., & Wray, S. (2005). A comparison of the contractile properties of human myometrium obtained from the upper and lower uterine segments. BJOG, 107(10), 1309-1311. https://doi.org/10.1111/j.1471-0528.2000.tb11626.x

Patterson, L. S., O’Connell, S. P., & Baskett, T. F. (2002). Maternal and perinatal morbidity associated with classic and inverted T cesarean incisions. Obstetrics & Gynecology, 100(4), 633-637. https://doi.org/10.1016/S0029-7844(02)02200-7