Some friends of mine at the Coalition for Breech Birth (a consumer advocacy organisation) have been discussing the role of practitioner experience in reducing risk associated with vaginal breech birth. My response is a bit longer than Facebook will permit, so I’m putting it here.

The study I find most useful in this discussion is here:

Su M, McLeod L, Ross S, Willan A, Hannah WJ, Hutton E, et al. Factors associated with adverse perinatal outcome in the Term Breech Trial. Am J Obstet Gynecol. 2003 Sep;189(3):740-5. PubMed PMID: 14526305. Epub 2003/10/04. eng.

Overall, the team found very few factors associated with an increase or reduction of risk of adverse perinatal outcome. They did find a dose-reponse relationship between amount of labour and adverse outcome. In other words, a pre-labour CS seemed to afford the most benefit, followed by early labour CS. By the time you are in active labour (>3 cm), there is no longer a statistically significant difference between CS and vaginal birth. So I get particularly annoyed when this study is used to tell women who arrive in advanced labour with an undiagnosed breech that a CS is the safest option.

They also found, contrary to popular belief, that big babies (>3500g) fared no worse than more averaged weight babies, but small babies (<2800g) did. Makes sense to me. Generally but not always, babies who are very small at term may already be slightly compromised; labour may be an additional stress. On the other hand, if a chunky 9-pounder folded in half can fit both his abdomen and his legs through your pelvis, chances are his head is going to fit, especially if you are with someone who knows how to help it into an optimal position.

He also needs to fit without help, because the study also revealed that using augmentation to enhance a labour which is not progressing well enough on its own was associated with over twice the risk of labours which proceeded spontaneously. Similarly, longer second stages increased the risk, so our baby needs to be descending fairly easily in the second stage, without help, or a CS may be the better option.

But the only factor shown to reduce the risk associated with a vaginal breech birth (by over 2/3) is the presence of an experienced clinician at the birth. This person need not be a licensed obstetrician, and the years of experience did not make a difference either – the TBT team specifically looked at these factors. The risk reduction occurred only when ‘an experienced clinician was defined as a clinician who judged him or herself to be skilled at vaginal breech delivery, confirmed by the Head of Department.’ Midwives were among those included in this definition.

Although we do not (yet) have any research (get back to me in a decade or so) which looks at the results of spontaneous breech birth with experienced clinicians at term, this analysis of the TBT suggests that this scenario is significantly less risky than many of the births included in the trial which were responsible for adverse outcomes. Add to that the further benefits we are seeing emerge with upright breech (reduction in need for manoeuvres and the minor injuries these can sometimes cause), and vaginal breech birth is a realistic option for many women.

One further comment on the research: Many are frustrated because the results of retrospective observational studies overwhelmingly indicate similar outcomes for vaginal breech birth and planned CS. These have comparatively little influence on guidelines because they are considered ‘biased.’ However, understanding why they are biased is sometimes useful. Retrospective studies are most often done by experienced practitioners who feel their own results conflict with the lowest common denominator represented by a large multi-centre RCT like the TBT. They present these results to illustrate that a comparatively safe vaginal breech service is possible, despite the fact that breech is often grossly mismanaged in many areas. Retrospective studies do not necessarily represent the ‘norm.’ But they do suggest, along with the TBT’s own data, that if your provider feels confident supporting you to have a vaginal breech birth, you can probably feel pretty confident as well.

Update 2015: A meta-analysis of observational studies indicates significantly better short-term outcomes when CS is planned than when VBB is planned. However, the rate of complications following planned VBB is much less than reported in the Term Breech Trial and similar to the results when a cephalic birth is planned. Read Berhan et al 2015 by clicking the link.

Shawn