Trial of Labor after C slides question

julyjennifer · April 2012

A link to these slides on recommendations for Trial of Labor after Cesarean (TOLAC) was posted below in response to another question. This is very interesting info. https://www.slideshare.net/bjebelli/vbac2010a

One of the recommendations was against a TOLAC when the previous C/S occurred at the 2nd stage, when the mom was fully dilated and pushing (also referred to in the slides as "failure of descent") In particular I'm looking at slides 18 and 34.

A good friend just had a c-section in this situation, so this interests me. Her baby was 10 lbs.

I'm wondering if anyone knows why the chances of a successful VBAC seem to be so low in this scenario. The slides seem to indicate it is only a 10-15% success rate, from what I can tell.

annabelle.27 · April 2012

Huh. I actually find that quite hard to believe. I had a c-section with my first after three hours of pushing, due to fetal malpositioning (OP with brow presentation). Everyone- the OB who did my c-section, the midwife who successfully delivered DS2, and my friend the L+D nurse- told me I would be a great candidate for a vbac, as there was nothing wrong with me, and that it was just poor positioning on my baby's part. They were right- I had a successful vbac two months ago with just two hours of labour from start to finish. Given that true CPD is supposed to be quite rare, I would think that many if not most c-sections given during the second stage of labour are due to fetal malpositioning, and I have a hard time believing that would somehow cause a 90% vbac failure rate in the future.

ETA: When I use this "prediction" calculator, it gives me a predicted success rate of 71% when I select "yes" to "Indication for prior cesarean of arrest
of dilation or descent?" and leave all other factors untouched, compared to 82% for responding "no" to that same question. Although this calculator still says that you'd have a lower success rate for arrest of dilation or descent, it's a far cry from the 10% the slides quoted...

https://www.bsc.gwu.edu/mfmu/vagbirth.html

This next link seems to state that results can vary widely. It references two studies, one that found that vbac attempts when the previous c-section occurred in second stage had a 13% success rate, and the second which found that the same vbac attempts had a 66% success rate

The success rate is much lower for patients whose labor arrested in the second stage: only 13% of patients who were fully dilated at the time of their prior delivery had a successful VBAC. In a similar study, patients who had their prior cesarean delivery in the first stage of labor had a lower rate of cesarean delivery than those who had their prior cesarean delivery in the second stage of labor. However, in this study, 66% of patients who had a cesarean delivery for dystocia in the second stage had a successful VBAC.

https://emedicine.medscape.com/article/272187-overview

The link below outlines more studies with vastly different conclusions, with success rates ranging from 13% to 75%.

https://www.homebirth.org.uk/vbchances.htm#point

It is interesting that results are all over the map, but I tend to believe the more favourable predictions myself.

iris427 · April 2012

That info is not really correct. There was one study that found a VBAC success rate of only 13% in moms who had a c/s at 10 cm. However, many other studies have found much higher success rates, like 60%+. I had my c/s at 10 cm and had a fast and uncomplicated VBAC and we have had many other posters here who also had successful VBACs in the same situation. The problem with looking only at the mother's dilation is it does not account for the reason for her cesarean. If it was for true CPD, sure she is probably not a great VBAC candidate. But if it was because of a undiscovered breech or fetal malposition, or the baby went into sudden distress or her provider was simply not patient enough, there is no reason the mother cannot have a VBAC like anyone else. In fact, one study has found that in mothers who had their c/s at 8 cm or more for an unrecurrent reason, they have VBAC success rates of 90%, probably because having dilated so much once already gives them an advantage going into their second labor. Even when you look at mothers who had a primary cesarean for CPD, success rates are often over 60%.

nosoup4u · April 2012

iris427:
In fact, one study has found that in mothers who had their c/s at 8 cm or more for an unrecurrent reason, they have VBAC success rates of 90%, probably because having dilated so much once already gives them an advantage going into their second labor.

This was the reason my MW and doula gave me for being confident I'd be able to VBAC with my second. She would always say that your body "remembers" how far it got, so since I got up to pushing, it'd be fine.

Which totally makes sense...women who've had a successful first vaginal birth don't worry about their bodies not being able to do it again, right? Ugh, all those studies make me angry.

honkytonk_kid · April 2012

I think at least part of the problem lies with provider bias. A provider who is not truly VBAC supportive might be going in thinking along the lines of "well I guess we can try, but she probably just can't push babies out." So at the first sign of delay/plateau/stall, they recommend a c/s instead of waiting it out.

Like iris said, true CPD mamas may have a low(er) chance of successful VBAC, but I'm a little wary of most provider's definition of CPD. I don't mean that to sound cynical or anti-OB, but in the absence of real evidence of anatomic issues (ie android pelvis, prior pelvis injuries, etc) I would nearly always err on the side of a TOLAC. There are just so many things that can factor into why the c/s happened in the first place- baby's size and position, induction, epidural, mom's ability to move around, etc- that can lead to a CPD diagnosis that I would never just assume a mama can't push future babies out. That's the problem with any of these VBAC success predictors- there are too many factors to consider.

iris427 · April 2012

honkytonk_kid:
I think at least part of the problem lies with provider bias. A provider who is not truly VBAC supportive might be going in thinking along the lines of "well I guess we can try, but she probably just can't push babies out." So at the first sign of delay/plateau/stall, they recommend a c/s instead of waiting it out.
Like iris said, true CPD mamas may have a low(er) chance of successful VBAC, but I'm a little wary of most provider's definition of CPD. I don't mean that to sound cynical or anti-OB, but in the absence of real evidence of anatomic issues (ie android pelvis, prior pelvis injuries, etc) I would nearly always err on the side of a TOLAC. There are just so many things that can factor into why the c/s happened in the first place- baby's size and position, induction, epidural, mom's ability to move around, etc- that can lead to a CPD diagnosis that I would never just assume a mama can't push future babies out. That's the problem with any of these VBAC success predictors- there are too many factors to consider.

ITA with all of this.

iris427 · April 2012

nosoup4u:
iris427:
In fact, one study has found that in mothers who had their c/s at 8 cm or more for an unrecurrent reason, they have VBAC success rates of 90%, probably because having dilated so much once already gives them an advantage going into their second labor.
This was the reason my MW and doula gave me for being confident I'd be able to VBAC with my second. She would always say that your body "remembers" how far it got, so since I got up to pushing, it'd be fine.
Which totally makes sense...women who've had a successful first vaginal birth don't worry about their bodies not being able to do it again, right? Ugh, all those studies make me angry.

My doctor and doula said the same thing. And good point in your second paragraph.

julyjennifer · April 2012

Thanks guys, this is all very interesting.

I'm glad to hear there's more to the story. It's interesting too that your body "remembers" that it can fully dilate, but makes sense to me. Depending on how far the first baby descended, you probably had a lot of things get stretched out down there, which can only help the second time around, I would think.

LindseyJW · April 2012

i guess it would depend on the reason for the failure to descend. i'm sure there is data out there on it.

i had a c/s for that reason. baby was OP, and i think lacked sufficient fontanels for molding. he wasn't big though, only 8.7 at almost 42 weeks. i pushed at home for 8hrs following more than 30hrs of labor before transferring for a c/s.

my hbac baby was slightly smaller at 7.9 and had plenty fontanels. labor start to finish was about 7hrs. i pushed for maybe 20 minutes.

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