Optimal timing for the ECV procedure
Current practice is to wait until 36 to 37 weeks to perform ECV, as most fetuses spontaneously move into vertex presentation by 36 weeks’ gestation. This time frame has several advantages: Many unnecessary attempts at ECV are avoided; only 8% of fetuses in breech presentation after 36 weeks spontaneously change to vertex5; many fetuses revert to breech if ECV is performed too early; and prematurity generally is not an issue in the rare case that immediate delivery is required during or just after attempted ECV.
ECV during labor. Performing ECV during labor appears to pose no increased risk to mother or fetus if membranes are intact and there are no other contraindications to the procedure. Some clinicians perform ECV only during labor. The advantages are that the fetus has had every chance to move into vertex presentation on its own, the equipment used to continuously monitor the fetus during ECV is in place, and cesarean delivery and anesthesia are immediately available in the event ECV is unsuccessful.
The major disadvantage of waiting until labor is that the increased size of the fetus makes ECV more difficult. In addition, the membranes may have already ruptured, and the breech may have descended deeply into the pelvis.
For the management of labor, patience is a virtue
Success rates in breech-to-vertex conversions
In 2016, the American College of Obstetricians and Gynecologists (ACOG) reported an average ECV success rate of 58% (range, 16% to 100%).6 ACOG noted that, with transverse lie, the success rate was significantly higher. Other studies have found a wide range of rates: 58% in 1,308 patients in a Cochrane review by Hofmeyr and colleagues7; 47% in a study by Beuckens and colleagues8; and 63.1% for primiparas and 82.7% for multiparas in a study by Tong Leung and colleagues.9 These rates were affected by whether ECV was performed with or without tocolysis, with or without intravenous analgesia, and with or without neuraxial analgesia/anesthesia (TABLE).
Likelihood of vaginal delivery after successful ECV
The rate of vaginal delivery after successful ECV is roughly half that of fetuses that were never in breech presentation.10 In successful ECV cases, dystocia and nonreassuring fetal heart rate patterns are the major indications for cesarean delivery. Some experts have speculated that the factors leading to near-term breech presentation—such as an unengaged presenting part or a mother’s smaller pelvis—also may be risk factors for dystocia in labor. Despite this, the rate of vaginal delivery of successfully verted babies has been reported to be as high as 80%.10
As might be expected, post-ECV vaginal deliveries are more common in multiparous than in primiparous women.
Although multiple problems may occur with ECV, generally they are rare and reversible. For instance, Grootscholten and colleagues found a stillbirth and placental abruption rate of only 0.25% in a large group of patients who underwent ECV.11 Similarly, the rate of emergency cesarean delivery was 0.35%. In addition, Hofmeyr and Kulier, in their Cochrane Data Review of 2015, found no significant differences in the Apgar scores and pH’s of babies in the ECV group compared with babies in breech presentation whose mothers did not undergo ECV.7 Results of other studies have confirmed the safety of ECV.12,13
One significant risk of ECV attempts is fetal-to-maternal blood transfer. Boucher and colleagues found that 2.4% of 1,244 women who underwent ECV had a positive Kleihauer-Betke test result, and, in one-third of the positive cases, more than 1 mL of fetal blood was found in maternal circulation.14 This risk can be minimized by administering Rho (D) immune globulin to all Rh-negative mothers after the procedure.
Even these small risks, however, should not be considered in isolation. The infrequent complications of ECV must be compared with what can occur with breech-presenting fetuses during labor or cesarean delivery: complications of breech vaginal delivery, cord prolapse, difficulties with cesarean delivery, and maternal operative complications related to present and future cesarean deliveries.
Alternative approaches to converting breech presentation of unproven efficacy
Over the years, attempts have been made to address breech presentations with measures short of ECV. There is little evidence that these measures work, or work consistently.
- Observation. After 36 weeks’ gestation, only 8% of fetuses in breech presentationspontaneously move into vertex presentation.5
- Maternal positioning. There is no good evidence that such maneuvers are effective in changing fetal presentation.15
- Moxibustion and acupuncture. Moxibustion is inhalation of smoke from burning herbal compounds. In formal studies using controls, these techniques did not consistently increase the rate of movement from breech to vertex presentation.16–18 Likewise, studies with the use of acupuncture have not shown consistent success in changing fetal presentation.19