VBAC After 2 Cesareans - Distorted Risk Perception

I recently wrote about ACOG's change in guidelines (August 2010), now "allowing" a trial of labor (TOL) again in women with 2 prior cesareans, whether or not they have had a prior vaginal birth.  This was a welcome change of policy and a breath of fresh air after many years of campaigning to get VBA2C back.

However, in the same post, I discussed the chilling effect that the earlier 2004 guidelines (which disallowed TOLs after 2 prior cesareans unless the woman had already had a prior vaginal birth) had had on the choices of women, and decried the reality that many women were forced into unnecessary repeat cesareans by these old guidelines.

The fact of the matter is that when ACOG makes these sweeping policy decisions (like all breeches should be born by cesarean, or VBAMC is not appopriate), it has MAJOR effects on the birthing climate in the world, effects that are not easily changed even if ACOG later recognizes its decisions were based on questionable research and changes its mind.

The net effect of disallowing VBAMC has been that only a few doctors in the world now "allow" women to choose a trial of labor after 2 prior cesareans, even though the risks associated with this have been shown to be reasonable. 

And although ACOG now "allows" a trial of labor after 2 cesareans, few OBs are rushing to change their policies.  The barn door is open, that horse is gone, and it's not coming back anytime soon.  I have hopes for change still, but I'm not holding my breath while waiting. The simple truth is that women are still being harmed by those old rules, even now.  ACOG has much to answer for.

This is similar to what has happened with breech births in the United States.  A flawed study came out that suggested that all breech babies were safer being born by cesarean, and BOOM, vaginal breech birth all but disappeared from the country, almost overnight.  Medical schools even quit teaching how to attend vaginal breech births, so many doctors now have no idea how to safely attend a surprise breech that shows up at the hospital. 

Research since the flawed breech study has questioned its conclusions and other recent studies have shown that vaginal breech birth is a reasonable option for most breech babies (and safer for the mother) ─ but it's close to too late to bring back the option because the art has been lost among so many providers.  Canada has been leading the way to try and get vaginal breeches re-established, but there's a long way to go.

As with breech, many doctors have developed an extremely distorted picture about risk with VBAC after two cesareans. 

And as with breech, all it took was one flawed study (Caughey 1999) that showed an abnormally high rate of rupture in VBA2C mothers, and ACOG rushed to virtually ban access to VBA2C. 

The problem is, that study had only 134 women in it, a sample size far too small to reliably determine risk (much less base sweeping policy decisions on); coincidence could easily have distorted the results.  No study before or since has shown such rates ─ but that didn't matter to ACOG.  It changed the rules, VBAMC was basically disallowed, and despite later research that showed the risk was not nearly as high as the Caughey study, VBAMC is still viewed by many as "far too risky" to even consider.  All on the basis of one very small, very flawed study.

Of course, some doctors have been overestimating the risk for uterine rupture in any VBAC  for years, but the degree of risk overestimation is especially egregious with VBA2C. 

Look at the following study, which surveyed doctors in France about their perceptions of the risks for uterine rupture with VBA1C and VBA2C.  The doctors overestimated the risk for rupture with both, but the overestimation was HUGE in the VBA2C group. 

In addition, they underestimated the risks associated with multiple repeat cesareans and counseled the women insufficiently about these.

As a result, less than a quarter of doctors surveyed would even consider "letting" a woman try a VBA2C trial of labor. 

The amazing thing is that this survey was published five years after major research showing far lower rupture rates in VBA2C mothers than these doctors estimated.

So what is the risk for rupture in VBA2C?  Studies vary, but the largest and most statistically powerful studies have shown rupture rates generally between 0.9% - 2.0% (Leung 1993, Miller 1994, Asakura 1995, Lin and Raynor 2004, Macones 2005, Landon 2006).

Tahseen and Griffiths (2010) did a meta-analysis of studies on VBA2C.  They found the average rupture rate was 1.36% and that the maternal morbidity between VBA2C and repeat cesarean was similar.

Note that all these studies include VBA2Cs with lots of induction and augmentation.  (Indeed, in Macones 2005, 16 of 19 ruptures in the VBA2C group were associated with induction or augmentation.)  With spontaneous labors only, the rupture risk for VBA2C would likely be even less.  (Never zero, alas, but less.)

What did the French doctors estimate the rupture risk to be with VBA2C?  14%!!!  Seven to fifteen times than the real risk.   

Distorted risk perception among doctors is one of the biggest things we battle on so many topics, from VBAC after multiple cesareans, to breech births, to pregnancy among women of size. 

AUGH.



Abstract

Vaginal birth after two previous c-sections: obstetricians-gynaecologists opinions and practice patterns. Doret M, Touzet S, Bourdy S, Gaucherand P.  J Matern Fetal Neonatal Med. 2010 Mar 17.

Hospices Civils de Lyon, Hôpital Femme-Mère-Enfant, Service d'obstétrique, F-69677 Bron, Lyon, France.

Objectives. To evaluate obstetricians' practice patterns, opinions and factors influencing decision-making about mode of delivery in women with two previous c-sections.

Methods. A questionnaire was mailed to the 160 obstetricians from the Rhone-Alpes perinatal network. Questionnaires included demographic, organisational information and questions about physicians' opinion, practice patterns and patient counseling concerning vaginal birth after c-section (VBAC) after one and two caesarean sections.

Results. Response rate was 65.6%; 100% and 23.8% would offer VBAC to women with respectively one and two previous c-sections.

Uterine rupture rate was largely overestimated in both women with one (2.8%) and two prior c-sections (14.2%).

Factors positively influencing obstetricians were cerebral palsy estimated rate less than 20%, a minimal decision to birth delay less than 20 min when emergency c-section would be required. Neonatal severe outcomes consecutive to trial of labour as well as placenta praevia or accreta risk and morbidity associated with multiple c-sections would be insufficiently discussed.

Conclusion. Obstetricians largely prefer a third planned c-section in women with two previous c-sections.

This decision is partly based on a large overestimation of immediate maternal and neonatal serious outcomes consecutive to trial of labour as well documented serious long term outcomes of multiple c-sections are insufficiently considered.  [sic]

PMID: 20233132