What was the Canadian Term Breech trial?

sri_cmicr_termbreech_logoA student midwife asked: “I have seen mention of the Canadian term breech research in journals, but googling this just takes me to various studies, and I know this was controversial research that was criticised but as I don’t know the history or how they fit together, I don’t know where to start with reading the critiques.  Is there a good overview?”

Yes, and you’re absolutely right; I couldn’t easily find a ‘beginner’ online overview either, so here we go.  Just bear in mind that, like any story, this is told from my perspective, and others might tell it slightly differently, or prioritise different elements of it.

The Canadian term breech trial was a study which began in 1997 with the aim of seeing whether vaginal birth or caesarean section was the safest option for babies who were presenting by the breech (that is, bottom first). The lead researchers (Hannah et al 2000) were based at the University of Toronto in Canada.

The idea was to assign women whose baby was breech randomly to ‘vaginal birth’ or ‘caesarean section’ in a randomised trial and then to look at the outcomes. We could then find out how many of the women and babies in each group were alive and well, look at who had problems and compare these within the two groups, thus finding out if one of these practices was safer and/or better than the other.  Because serious problems are (happily) quite rare, researchers need as many people as possible in their studies in order to get good data, so this was a multi-centre trial, which means that data is collected from lots of other centres (in this case hospitals) around the world.  In total, 26 countries contributed data to this study.

Originally, the research was going to continue for five years, but the researchers decided to stop the trial early and publish the results, because they felt that the data was showing that caesarean section was a far better and safer option than vaginal birth for breech babies.  The results were published in The Lancet (Hannah et al 2000) and here’s the abstract:

BACKGROUND: For 3-4% of pregnancies, the fetus will be in the breech presentation at term. For most of these women, the approach to delivery is controversial. We did a randomised trial to compare a policy of planned caesarean section with a policy of planned vaginal birth for selected breech-presentation pregnancies.
METHODS: At 121 centres in 26 countries, 2088 women with a singleton fetus in a frank or complete breech presentation were randomly assigned planned caesarean section or planned vaginal birth. Women having a vaginal breech delivery had an experienced clinician at the birth. Mothers and infants were followed-up to 6 weeks post partum. The primary outcomes were perinatal mortality, neonatal mortality, or serious neonatal morbidity; and maternal mortality or serious maternal morbidity. Analysis was by intention to treat.
FINDINGS: Data were received for 2083 women. Of the 1041 women assigned planned caesarean section, 941 (90.4%) were delivered by caesarean section. Of the 1042 women assigned planned vaginal birth, 591 (56.7%) delivered vaginally. Perinatal mortality, neonatal mortality, or serious neonatal morbidity was significantly lower for the planned caesarean section group than for the planned vaginal birth group (17 of 1039 [1.6%] vs 52 of 1039 [5.0%]; relative risk 0.33 [95% CI 0.19-0.56]; p<0.0001). There were no differences between groups in terms of maternal mortality or serious maternal morbidity (41 of 1041 [3.9%] vs 33 of 1042 [3.2%]; 1.24 [0.79-1.95]; p=0.35).
INTERPRETATION: Planned caesarean section is better than planned vaginal birth for the term fetus in the breech presentation; serious maternal complications are similar between the groups.

small__2729938953Almost as soon as it had been published, however, other researchers, practitioners and consumer groups began to spot problems with the methods that had been used to carry out the research.  They realised that there were so many issues with the way in which the research was designed and carried out that its findings could not be relied upon.  People started to publish critiques and articles discussing these, and the conversation grew and grew.  The concern was international, and although the authors tried to defend their work, most people now believe the results of this trial to be of little value.  However, there is concern about the impact of the trial on midwives’ and obstetricians’ skills in vaginal breech birth, although some independent midwives and a few hardy obstetricians and midwives working within the system in different countries continued to attend breech births throughout this time.  Change is now happening, though it is a slow, uphill battle in some areas.

So here are a few resources to surf around, and several of these offer links elsewhere too, like this one, which has a good overview if you need more and links to several of the related articles and later research 🙂


Canadian Term Breech Trial Resources

As several of these papers discuss and reference the ongoing and related research, I’ll not repeat all that here, but I hope this helps you find a clearer way through the maze.


photo credit: paul bica via photopin cc

Want to stay up to date and get regular updates on birth-related research and thinking sent free to your inbox?

Sign up to my newsletter list.

Books to help you become informed and make the decisions that are right for you…

If this blog post or any of my work has helped you or those you care for, please buy me a coffee and help me continue to provide independent birth information online as well as in my books.

Thank you 💜

2 comments for “What was the Canadian Term Breech trial?

Comments are closed.