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?
The waning of vaginal breech deliveries in many developed countries (including the United States and Canada) further increases the risks of these births. In a survey of Canadian obstetricians regarding management of breech presentation at term, 69% of respondents felt that Canadian residents-in-training were insufficiently experienced to safely manage a trial of labor and vaginal delivery for mothers with frank breech presentations at term.5 The declining numbers of clinicians experienced in vaginal breech delivery also made it necessary for the authors of the Term Breech Trial to include centers from developing countries in order to recruit enough participants. The inclusion of these centers was probably a net strong point, since intended vaginal birth is standard, rather than exceptional, in most developing countries. That is, obstetricians in these countries are probably more experienced in vaginal breech delivery than their counterparts in developed nations.
The fact that elective cesarean failed to reduce neonatal morbidity in countries with a high PMR may have been due to this greater level of experience. However, the perinatal or neonatal mortality rate among women randomized to intended vaginal delivery in these countries was 3 times greater than the perinatal mortality rate among women undergoing elective cesarean section. Thus, it is possible that babies born with problems attributable to intended vaginal birth died—instead of becoming survivors with serious morbidity.
Because the authors of the Term Breech Trial knew that many obstetricians would be disappointed by the findings, they conducted a number of subanalyses. They performed regression analysis looking for significant interactions between the treatment group and a number of factors for the combined outcome of perinatal mortality, neonatal mortality, and serious neonatal morbidity. These factors included parity, type of breech presentation, gestational age, presence of labor, presence of ruptured membranes, estimated fetal weight, method of assessing attitude of the fetal head, and method of assessing pelvic adequacy. They found no significant interaction between the treatment group and these factors. That is, they were unable to identify a subgroup for whom the effect of the 2 treatments on the combined outcome was equivalent.
The authors also analyzed their data according to years of experience of the practitioner present at each vaginal delivery. They found an advantage to the fetus/infant for elective cesarean section even among infants delivered by obstetricians with more than 20 years of experience in vaginal breech delivery. The authors analyzed their data excluding vaginal breech deliveries that occurred after prolonged labor, after induced or augmented labor, deliveries in which a footling or uncertain breech was present, and deliveries in which no skilled clinician was present. They also analyzed their data excluding women having a vaginal breech delivery without epidural anesthetic. They found an advantage to the fetus for cesarean delivery in all the subgroups analyzed.
Are the results generalizable?
A major question clinicians must address when interpreting the results of any randomized controlled trial (RCT) is whether they are generalizable to the practice of medicine in the clinician’s own setting. One concern raised by many RCTs is that conditions in the university hospitals in which most trials are carried out may differ from those in most practice environments. Out of necessity, the Term Breech Trial included a wide variety of community and university settings, as well as more than 2 dozen countries. The authors anticipated the problem of different styles of practice by laying out a very clearly defined study protocol, with strict guidelines for eligibility and intrapartum management drawn from the Canadian consensus conference.3 In addition, by classifying countries according to the PMR, the authors ensured that the findings would be applicable in both developed and developing nations.
Although it would be beneficial to compare the results of the Term Breech Trial with those of future multicenter RCTs on the subject, the Term Breech Trial yields solid data. And since the number of obstetricians experienced in vaginal breech delivery continues to decline in the developed world, this trial is likely to be the only large-scale evidence we will ever have. Its findings are certainly much more reliable than those of the small RCTs and observational studies that preceded it.
Although it affects only 3% to 4% of term pregnancies, the breech presentation is thought to occur in as many as 50% of gestations prior to 32 weeks.1 Most of these early breech presentations resolve spontaneously, converting to a cephalic position as the pregnancy progresses. Attempts to facilitate version in the remainder of breech pregnancies typically involve external manipulation, i.e., external cephalic version (ECV), as the fetus nears term.
The power of suggestion.In recent years, alternative approaches have proven effective to some degree. In a prospective case series conducted in the early 1990s, 100 gravidas with breech-presenting fetuses at 37 to 40 weeks’ gestation were treated with hypnosis and matched with a historical control group of women with similar obstetric and sociodemographic characteristics.1 Subjects were given hypnotic suggestions for relaxation and the easing of fear and anxiety and were asked why their babies were in the breech position. They received as much hypnosis as possible—barring inconvenience—until the infant converted to the cephalic position or was delivered. Hypnosis was judged to be effective if the infant converted spontaneously or if subsequent ECV was successful. Eighty-one percent of fetuses in the treatment group converted to cephalic presentation by the time of delivery compared with 48% in the control group, a statistically significant difference.
Asian tradition.The ancient Chinese practice of moxibustion—the application of heat to acupoint BL 67 from a burning, cigar-shaped roll of herbs—was tested in a randomized controlled trial conducted in Nanchang, China.2 Because moxibustion is a popular remedy for breech presentation in China, it was impossible to use “sham” moxibustion as a placebo for the control group. (Controls received routine prenatal care but no interventions for breech presentation.) When the smoldering preparation of mugwort, known as “moxa” in Japan, was held beside the outer corner of the fifth toenail, fetal activity increased and conversion to the cephalic position occurred in 98 of 130 fetuses (75.4%) in the treatment group—82 of them during the first week of treatment—compared with 62 of 130 fetuses (47.7%) in the control group. During treatment, the women were asked to record the number of active fetal movements for 1 hour each day. The mean number of fetal movements during a 7-day period was 48.45 for women treated with moxibustion compared with 35.35 for the controls. Researchers postulated that moxibustion acts by increasing fetal movements, although there is evidence that it also affects maternal plasma cortisol and prostaglandin levels.3,4
The tried and true.ECV itself is a very old procedure, having been described in the literature as early as 1860.5 Before the development of imaging technologies, fetal presentation was determined using Leopold’s maneuvers, and version typically was performed without tocolysis or sedation, with poor success rates. Today, breech presentations are confirmed by ultrasound imaging, which also yields information on the type of breech and the positioning of the fetal spine, neck, and head. Along with estimated fetal weight, these factors are useful in predicting the success of ECV for a given patient. Fewer than 10% of successfully converted fetuses return to the breech position.
A prospective study of pregnancy outcomes after successful ECV found a higher risk of dystocic labor and fetal distress than for pregnancies with spontaneously occurring cephalic presentation, suggesting that the cephalic position per se does not completely eliminate the risk of cesarean delivery.6 Among the pregnancies in which ECV was successful, the incidence of intrapartum cesarean deliver was 16.9%—2.25 times higher than for controls (P<.005).
REFERENCES
1. Mehl LE. Hypnosis and conversion of the breech to the vertex presentation. Arch Fam Med. 1994;3(10):881-887.
2. Cardini F, Weixin H. Moxibustion for correction of breech presentation. A randomized controlled trial. JAMA. 1998;280(18):1580-1584.
3. Cooperative Research Group of Moxibustion Version of Jangxi Province Studies of version by moxibustion on Zhiyin points. In: Xiangtong Z, ed. Research on Acupuncture, Moxibustion and Acupuncture Anesthesia. Beijing: Science Press; 1980:810-819.
4. Cooperative Research Group of Moxibustion Version of Jangxi Province. Further studies on the clinical effects and the mechanism of version by moxibustion. In: Abstracts of the Second National Symposium on Acupuncture, Moxibustion and Acupuncture Anesthesia. August 7-10, 1984; Beijing, China.
5. Classic pages in obstetrics and gynecology: on a new method of version in abnormal labour. John Braxton Hicks. Lancet. 1860;2:28-30 and 55.Am J Obstet Gynecol. 1976;125(5):711.-
6. Lau TK, Lo KW, Rogers M. Pregnancy outcome after successful external cephalic version for breech presentation at term. Am J Obstet Gynecol. 1997;176(1 Pt 1):218-223.
