Looking back on the Term Breech Trial: To what extent does scientific literature influence doctor practice?

What impact might a seemingly robust study that was subsequently refuted have had on doctors' practices? That’s the question posed by three health economists whose previous work had focused, among other things, on explaining the increase in cesarean section rates in the United States and Canada since the 1990s.The study in question, called the Term Breech Trial, was published in 2000 in the Lancet, a journal renowned for its reliability. This randomized trial, conducted in 121 centres in 26 countries, concluded that breech babies have better short- and medium-term health outcomes if delivered by cesarean section, implying that their vaginal delivery is riskier.In the wake of this research, several learned societies of gynecology-obstetrics in North America and Europe adapted their guidelines accordingly, recommending cesarean delivery of breech babies. However, in 2004, one study—subsequently reinforced by others—contradicted the Term Breech Trial. It demonstrated that, taking into account the experience of the doctors and the characteristics of the patients who took part in the trial, the health indicators of breech babies born by cesarean section were no better than those born vaginally.Investigating responseMaripier Isabelle, associate professor in the department of economics at Université Laval in Quebec City and her colleagues Philip DeCicca from Ball State University in Indiana and Natalie Malak from the University of Alabama, wanted to know more. “It's not every day that a high-profile medical study is called into question,” she pointed out. “So we wanted to find out whether the Term Breech Trial had induced changes in doctors’ practices, and how they adjusted after it was challenged.”To do this, the researchers collated and analyzed U.S. birth data between 1995 and 2010. They covered about 28 million deliveries, including more than 750,000 cases of breech babies, for which they had newborns’ health check-ups during their first years of life. The three then compared cesarean section rates before the publication of the Term Breech Trial, over the following four years (from 2000 to 2004), and after the publication of the first article contradicting the study (from 2004 to 2010). They also used a control group of babies who presented by the head.Their results, published in early July in the journal Health Economics, speak for themselves. “The Lancet publication had no significant effect on the cesarean section rate for breech babies at term in the U.S.,” said Isabelle. This rate, which was 78.4% before 2000, rose to 80% between 2000 and 2004. "This small impact is probably because the C-section rate in such circumstances was already very high in the United States.” On the other hand, in other countries, such as Denmark, where C-section rates for breech babies were lower, the Term Breech Trial had a significant impact in a very short space of time.Notably, after 2004, “We saw a significant and rapid reduction in this rate, which surprised us. Obstetricians adjusted their practices very quickly, whereas the literature shows that, in general, changes in physicians’ practices are usually much more slowly.” Between 2004 and 2010, the cesarean section rate in breech cases fell to 66%. This drop is all the more surprising given that, during the period studied by the three researchers, the C-section rate for head-first babies rose from 6.6% to 11.4% in the U.S.As for the health outcomes of the babies concerned, “If the Term Breech Trial were true, we should have seen health effects in breech babies born vaginally after 2004. But there were none,” pointed out Isabelle, who concludes that the studies that criticized the Lancet article were “potentially right.”The researchers also observed that the reduction in the cesarean section rate for breech babies was more pronounced among young doctors, doubled in fact, compared with more experienced clinicians. Isabelle sees several possible explanations. “Obstetricians at the beginning of their careers have less ingrained practice habits and are potentially more connected to research.” She also speculates that some of their more experienced peers, who could, for example, master the technique of turning the baby in utero, may have overlooked the findings of the Term Breech Trial.Finally, the last thing that surprised the researchers had to do with the media attention of the Lancet article, while the articles that contradicted it did not receive the same media treatment. “High-profile studies influence patient demand. We might therefore have expected the Term Breech Trial to have an impact on patients, but that doesn't seem to have been the case,” said Isabelle. In her opinion, the changes in medical practice, which remain quite contextual, come more from the provision of care, i.e., from clinicians, than from patient demand.

Looking back on the Term Breech Trial: To what extent does scientific literature influence doctor practice?

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