Methods to facilitate ECV success
Two techniques that can facilitate ECV success are tocolysis, which relaxes the uterus, and neuraxial analgesia/anesthesia, which relaxes anterior abdominal wall muscles and reduces or relieves ECV-associated pain.
In tocolysis, a medication is administered to reduce myometrial activity and to relax the uterine muscle so that it stretches more easily around the fetus during repositioning. Tocolytic medications originally were studied for their use in decreasing myometrial tone during preterm labor.
Tocolysis clearly is effective in increasing ECV success rates. Reviewing the results of 4 randomized trials, Cluver showed a 1.38 risk ratio for successful ECV when terbutaline was used versus when there was no tocolysis. The risk ratio for cesarean delivery was 0.82.20 Fernandez, in a study of 103 women divided into terbutaline versus placebo groups, had a 52% success rate for ECV with the terbutaline group versus only a 27% success rate with the placebo group.21
Tocolytic medications include terbutaline, nifedipine, and nitroglycerin.
Tocolysis most often involves the use of β2-adrenergic receptor agonists, particularly terbutaline (despite the boxed safety warning in its prescribing information). A 0.25-mg dose of terbutaline is given subcutaneously 15 to 30 minutes before ECV. Clinicians have successfully used β2-adrenergic receptor agonists in the treatment of patients in preterm labor, and there are more data on this class of medications than on other agents used to facilitate ECV.
Although nifedipine is as effective as terbutaline in the temporary treatment of preterm uterine contractions, several studies have found this calcium channel blocker less effective than terbutaline in facilitating ECV.22,23
The uterus-relaxing effect of nitroglycerin was once thought to make this medication appropriate for facilitating ECV, but multiple studies have found success rates unimproved. In some cases, the drug performed more poorly than placebo.24 Moreover, nitroglycerin is associated with a fairly high rate of adverse effects, such as headaches and blood pressure changes.
Over the past 2 decades, there has been a resurgence in the use of neuraxial analgesia/anesthesia in ECV. This technique is more effective than others in improving ECV success rates, it reduces maternal discomfort, and it is very safe. Specifically, it relaxes the maternal abdominal wall muscles and thereby facilitates ECV. Another benefit is that the anesthesia is in place and available for use should emergency cesarean delivery be needed during or after attempted ECV. Neuraxial anesthesia, which includes spinal, epidural, and combined spinal-epidural techniques, is almost always used with tocolysis.
The major complications of neuraxial analgesia/anesthesia are maternal hypotension and fetal bradycardia. Each is dose related and usually transient.
In the past, there was concern that using regional anesthesia to control pain would reduce a patient’s natural warning symptoms and result in a clinician applying excessive force, thus increasing the chances of fetal and maternal injury and even fetal death. However, multiple studies have found that ECV complication rates are not increased with use of neuraxial methods.
Higher doses of neuraxial anesthesia produce higher ECV success rates. This dose-dependent relationship is almost surely attributable to the fact that, although lower dose neuraxial analgesia can relieve the pain associated with ECV, an anesthetic dose is needed to relax the abdominal wall muscles and facilitate fetus repositioning.
The literature is clear: ECV success rates are significantly increased with the use of neuraxial techniques, with anesthesia having higher success rates than analgesia. Reviewing the results of 6 controlled trials in which a total of 508 patients underwent ECV with tocolysis, Goetzinger and colleagues found that the chance of ECV success was almost 60% higher in the 253 patients who received regional anesthesia than in the 255 patients who received intravenous or no analgesia.25 Moreover, only 48.4% of the regional anesthesia patients as compared with 59.3% of patients who did not have regional anesthesia underwent cesarean delivery, roughly a 20% decrease. Pain scores were consistently lower in the regional anesthesia group. Multiple other studies have reported similar results.
Although the use of neuraxial anesthesia increases the ECV success rate, and decreases the cesarean delivery rate for breech presentation by 5% to 15%,25 some groups of obstetrics professionals, noting that the decreased cesarean delivery rate does not meet the formal criterion for statistical significance, have expressed reservations about recommending regional anesthesia for ECV. Thus, despite the positive results obtained with neuraxial anesthesia, neither the literature nor authoritative professional organizations definitively recommend the use of neuraxial anesthesia in facilitating ECV.
This lack of official recommendation, however, overlooks an important point: While the cesarean delivery percentage decrease that occurs with the use of neuraxial anesthesia may not be statistically significant, the promise of a pain-free procedure will encourage more women to undergo ECV. If the procedure population increases, then the average ECV success rate of roughly 60%6 applies to a larger base of patients, reducing the total number of cesarean deliveries for breech presentation. As only a small percentage of the 110,000 to 150,000 women with breech presentation at 36 weeks currently elects to undergo ECV, any increase in the number of women who proceed with attempts at fetal repositioning once procedural pain is no longer an issue will accordingly reduce the number of cesarean deliveries for the indication of malpresentation.
Nitrous oxide for labor pain
Overarching goal: Reduce cesarean delivery rate and associated risks
In the United States, increasing the use of ECV in cases of breech-presenting fetuses would reduce the cesarean delivery rate by about 10%, thereby reducing recovery time for cesarean deliveries, minimizing the risks associated with these deliveries (current and future), and providing the health care system with a major cost savings.
Tocolysis and the use of neuraxial anesthesia each increases the ECV success rate and each is remarkably safe within the context of a well-defined protocol. Reducing the pain associated with ECV by administering neuraxial anesthesia will increase the number of women electing to undergo the procedure and ultimately will reduce the number of cesarean deliveries performed for the indication of breech presentation.
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