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Clinical Reviews

The term breech: vaginal or cesarean delivery?

The Term Breech Trial has been hailed for shining light on the murky question of how best to deliver term breech infants. But does it really?

January 2002 · Vol. 14, No. 1

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.

Vaginal delivery

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.

The rate of successful vaginal delivery—when attempted—also differs markedly between the subgroups, from 68.3% in countries with high perinatal mortality to 44.7% in those with low perinatal mortality. Two reputable studies have determined the success rate of well-selected breech trials of labor to be around 70%.3,4 The 56.7% overall success rate in the Term Breech Trial raises questions about eligibility and selection criteria, and also about the variability in operator characteristics.

Another potential source of variability is the use of conduction analgesia in breech trials of labor. Normal, spontaneous progress in the first stage of labor, with optimal maternal expulsive forces and cooperation in the second stage of labor, is highly desirable for vaginal breech delivery. Inefficient maternal pushing in the second stage will expose the fetus to intravaginal manipulations that could jeopardize its well-being.

It appears that—at least in some cases—epidural analgesia has the potential to cause uterine hypocontractility and a prolonged, inefficient second stage of labor. For this reason, some skilled operators believe that epidural analgesia is best avoided in a breech trial of labor.5 We are not at all surprised that among the women in the Term Breech Trial who were able to deliver vaginally (in the group assigned to vaginal delivery), only 25.1% received epidural analgesia. What we do not understand is why a repeat analysis was performed after excluding the vaginal deliveries that did not involve epidural analgesia. Just the opposite might have been interesting: a repeat analysis after excluding the cases with epidural analgesia! Or, instead of an arbitrary stratification based on national PMR statistics—which might be totally irrelevant for the level of care in the particular institutions selected to participate in the study—stratification based on clinical factors such as the availability and use of epidural analgesia might have been more meaningful.

The selection process

The development of inclusion criteria was undoubtedly the first step in selecting appropriate candidates for the breech trial of labor. In practice, however, there is a second step in the selection process: the observation of labor abnormalities that might disqualify cases previously considered appropriate. In the Term Breech Trial, this second step was likely highly variable. For many experienced practitioners, conditions such as premature rupture of membranes (PROM), an absence of spontaneous labor, uterine hypocontractility, or an abnormal labor curve would prompt a reconsideration of the mode of delivery. Some experts believe that any arrest of spontaneous progress in labor necessitates cesarean section.6 Contrary to that, in the Term Breech Trial, as many as 22.4% of the cases assigned to planned vaginal birth had PROM, an unspecified number were induced, and a significant number of cases had augmented labor. Even Brenner, one of the few authors to conclude that the induction of labor is acceptable for women with breech presentations, noted that labor augmentation is associated with higher rates of infant mortality and morbidity.7

The authors conducted another repeat analysis after excluding 335 cases in which labor was induced or augmented, presentation was footling, or supervision was inadequate. These excluded cases, which account for 32% of the total for planned vaginal delivery, were responsible for 55.7% of the total adverse outcomes in that group only. This suggests that poor eligibility criteria may have contributed to an increased risk of fetal injury.

Does the trial reflect the customary clinical approach to breech presentation in labor or, rather, suggest that the operators felt bound by the randomized assignment? Is the higher rate of successful vaginal delivery in countries with high perinatal mortality indicative of greater operator experience with vaginal breech births (as speculated by the authors), or were the operators simply not as quick to resort to cesarean delivery, compared with their counterparts in countries with low perinatal mortality?

Interpreting outcomes

The authors’ interpretation of their results sometimes defies clinical plausibility. For example, in regard to the 16 cases of perinatal mortality, is it conceivable that the neonatal death from possible gastroenteritis in one infant who had been discharged home well, or the sudden infant death syndrome (SIDS) in a low-birth-weight infant also discharged home well, or the neonatal deaths from respiratory problems in possibly premature newborns might be attributed to something other than the mode of delivery? Also included are cases of intrapartum death with “fetal heart tones disappearing before a cesarean section could be done.” Such cases could reflect labor management rather than consequences attributable to mode of delivery.

We also are unconvinced by the authors’ contention that “the avoidance of labor…could have contributed to better outcomes.” The same logic could be extended to any woman in labor—whether presentation is cephalic or breech. An overall policy of planned cesarean section would prevent complications of labor because there would be no labor! Only 3 cases of perinatal death appear to be related to a difficult vaginal breech delivery in the group randomized to planned vaginal birth, equal to the rate of perinatal mortality in the planned-cesarean-delivery group.

The interpretation of cases involving serious neonatal morbidity also appears subjective and speculative. How serious are the 5 cases of brachial plexus injury in the vaginal-delivery group when most were already improving 2 to 4 days after delivery? Further, measures of neonatal morbidity such as the Apgar score are influenced by the subjectivity of unblinded caregivers and rarely signify long-term morbidity. Intracerebral or intraventricular hemorrhage, another measure of neonatal morbidity, also may be unrelated to the mode of delivery,8 whereas measures of serious neonatal morbidity such as spinalcord injury or basal skull fracture actually occurred in the planned-cesarean group.

Even if we accept the alarming rates of serious neonatal morbidity presented in the study—1.4% in the planned-cesarean group versus 3.8% in the planned-vaginaldelivery group—the risk differential, also known as the attributable risk (the difference attributable to a trial of labor) is only 2.4%. For practical purposes, this means that among 100 women with breech presentation, a trial of labor is associated with 2 more undesired outcomes on average than if there were no trial of labor. Applying the same reasoning for the 0.2% difference in prolonged NICU admissions, among 1,000 women with breech presentation, a trial of labor is associated with only 2 more prolonged NICU admissions (longer than 4 days) than if there were no trial of labor.

The middle road: deciding case by case

Martin L. Gimovsky, MD
Professor and Vice Chairman Department of OBG Director, Maternal-Fetal Medicine Newark Beth Israel Medical Center Newark, NJ

While the design of the Term Breech Trial was exceptional and the data it yielded valuable, I do not believe it definitively answered the question of which mode of delivery is best for breech presentations at term—vaginal or cesarean. Rather, I would argue for making that decision on a case-by-case basis.

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