Until Mary E. Hannah and her colleagues conducted the randomized controlled study known as the Term Breech Trial (published in the October 21, 2000, issue of the Lancet), data on the best delivery method for breech infants at term were sketchy and conflicting. Still, elective cesarean generally was preferred when the breech presentation was footling; the fetus was large, compromised, or had a congenital abnormality that could complicate vaginal delivery; or when a physician experienced in vaginal breech delivery was unavailable. However, the optimal mode of delivery for all other term breech fetuses remained unclear at best—at worst, controversial.
The Term Breech Trial spanned 26 countries and involved 2,088 women with a frank or complete breech presentation at term (37 weeks and later). Of the 1,041 women allocated to planned cesarean delivery, 941 (90.4%) were delivered by C-section, while 591 of the 1,042 women (56.7%) assigned to the vaginal group were delivered vaginally. An experienced clinician was present during all vaginal deliveries. The primary outcomes analyzed were perinatal or neonatal mortality and serious neonatal morbidity, which were significantly lower for the planned-cesarean group than for the vaginal-delivery group (1.6% versus 5%). For the outcomes of maternal mortality and serious maternal morbidity, there were no real differences between the groups.
Baseline characteristics of the women, infants, hospitals, countries, prenatal care, and labor were used to group the women different ways to determine whether there was an interaction between a characteristic and the treatment group for the primary outcomes. The only significant interactions involved a country’s perinatal mortality rate (PMR), as reported by the World Health Organization (WHO), and serious neonatal morbidity. Specifically, in countries with a low PMR, planned cesarean section had much greater benefits for the infant than in the trial group as a whole. In countries where the PMR is high, the benefits of planned cesarean were much lower than in the entire trial group. Because of this, researchers concluded, as many as 39 additional cesareans might be needed to avoid one infant’s serious morbidity or death in countries with a high PMR compared with as few as 7 additional C-sections in countries with a low PMR. For the study group as a whole, 14 additional cesareans would have to be performed to prevent one infant’s death or serious morbidity.
Although many clinicians now believe the mode of delivery for term breech infants clearly should be elective cesarean, particularly since the American College of Obstetricians and Gynecologists (ACOG) issued a committee opinion in favor of it in December 2001, that outlook isn’t universal. Here, 4 experts weigh in. Favoring elective cesarean is Ellen Mozurkewich, MD, MS. Arguing against relegating vaginal breech delivery to “the shelves of history” are Alex C. Vidaeff, MD, and Edward R. Yeomans, MD. And Martin L. Gimovsky, MD, makes the case for individualizing treatment.
Rarely should a single medical article alter the way physicians practice. Even the randomized controlled trial (RCT), the “gold standard” of medical research, is subject to scrutiny. The Term Breech Trial is undoubtedly a remarkable scientific undertaking.1 The way it was designed and conducted lends substantial weight to its conclusions. But is it such a perfect and convincing work that we can confidently accept it as the “last word” and relegate a whole chapter of practical contemporary obstetrics to the shelves of history? We think not, and we summarize our reasons below.
The problem: variability in exposure
Variability in the conduct of vaginal breech delivery (also called “exposure”) can produce differences in outcomes and lead to false inferences. Hannah et al attempted to control for the significant differences in practice patterns among operators in the 26 participating countries by stratifying those countries according to their national PMR, creating 2 subgroups: high and low PMR. But this stratification criterion seems arbitrary. For example, we know firsthand that the technical approach to vaginal breech delivery in Romania and the United States, both of which fall into the low-PMR category, is as different as night and day, and we presume that such differences exist between other countries as well—within subgroups. (As an intern, Dr. Vidaeff learned to conduct vaginal breech deliveries in Romania.)
Many foreign practitioners adhere to the principle of noninterference during vaginal breech births until spontaneous delivery of the scapulae occurs (or even later, according to the Vermelin or Burns-Marshall’s methods). However, in the United States and Canada, operator intervention begins when the fetus is delivered to the level of the umbilicus.2 Such technical differences may account for varying outcomes, and no statistical test can tell us which covariates (independent variables) have been omitted or underestimated in the analysis. Further, maneuvers such as the Bracht maneuver, very popular in Europe, are ignored in the United States and Canada, whereas the Piper forceps, frequently used in North America, is unknown in some parts of the world.