Intravenous Nitroglycerin for External Cephalic Version
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: A study showing some benefit of uterine relaxation with IV nitroglycerin in external version exemplifies, along with other studies, how many patients with breech presentations today can avoid the need for Cesarean section.
Source: Hilton J, et al. Intravenous nitroglycerin for an external cephalic version. Obstet Gynecol 2009;114:560-567.
Three to 5% of patients at term will have breech presentations, and in most countries 90% of these patients will be delivered by Cesarean section. With a Cesarean section rate in the United States > 30%, there has been some effort to circumvent the need for Cesarean section in patients motivated to have a vaginal delivery by attempting, in a variety of ways, external version (EV).
Hilton et al conducted a randomized clinical trial in which IV nitroglycerin was used to relax the uterus during EV. One hundred twenty women with breech presentations were recruited for the study — 82 were nulliparas and 44 were multiparas. About half in each group received 100 µg of nitroglycerin in 10 mL of diluent. The other half received saline. If the version was unsuccessful due to inadequate relaxation, a second dose was administered after 30 minutes and the EV was reattempted.
In nulliparas, the success rate was 24% with nitroglycerin vs 8% in the placebo group (P = 0.04), and in the multiparas, the difference was not statistically significant between treated and control groups (44% vs 43%), but there was a reasonable success rate of version alone. Side effects were minimal and, surprisingly, hypotension occurred as frequently in the placebo group as in the treatment group. Nine patients in this study described pain during the procedure as being "intolerable," resulting in the procedure being abandoned.
Commentary
In 2000, the Hannah et al randomized trial, suggesting a higher rate of perinatal morbidity and mortality in breech fetuses delivered vaginally compared with Cesarean section,1 put a nail in the coffin of vaginal delivery for breeches. A cost-analysis from 1993 showed that breeches were responsible for 15% of our Cesarean sections and they ate up $1.4 billion annually in health care dollars (obviously an under-estimate when considering 2009 figures). Also, importantly, some patients today are highly motivated to try anything to avoid Cesarean section.
The literature is filled with small studies involving various methods to convert a breech to a vertex, and some are more elaborate than others. The above study seems to show that nitroglycerin works reasonably well as an adjunct in converting breeches in the most difficult patient category — nulliparas. However, it does not seem to add anything in multiparas, in whom EV worked in about half of patients without the need for other help. Although many clinicians use medications such as terbutaline, ritodrine, and nifedipine for the same effect, it does seem likely that nitroglycerin would provide the ultimate short-acting uterine relaxation (to which any clinician who has used it to deliver a second twin can attest). Nevertheless, there appears to be more to version than uterine relaxation, such as operator experience and lowering maternal pain and anxiety. Here the literature provides conflicting results regarding the use of epidural or spinal anesthesia. One study showed no benefit from spinal anesthesia (49% vs 51%),2 while another study did show benefit (67% vs 32%),3 compared with controls. In yet another interesting paper, Rozenberg et al first tried converting 169 breeches at 36-37 weeks using a beta-mimetic (salbutamol) as a uterine relaxant.4 They were successful in 56.8%. They then enrolled 68 of the remaining 73 patients to have epidural anesthesia. Seventy-two percent of these patients were nulliparas. In 27 patients (39%) the investigators were successful, with a combined success rate of 68% in multiparas and 28.6% in nulliparas.
Finally, "alternative" methods have also yielded modest success with far less fanfare, risk, and cost. For example, there have been a few studies showing some success with acupuncture. One such study worth mentioning involved a randomized trial by Neri et al, billed as the first study of its kind in a "Western" pregnant population (Italy).5 Two hundred twenty-six women with breeches between 33 and 35 weeks had a combination of acupuncture and moxibustion applied to a specific acupoint (BL67). At delivery, 53.6% of the treated group of 112 patients showed up with vertex presentations vs 36.7% of the 114 patient controls (P = 0.01).
So, today there are some options open to those patients with breeches wishing preemptive measures to avoid Cesarean section. The first would be the seemingly innocuous acupuncture approach at 33-35 weeks. The next would be to attempt a version with a uterine relaxant such as nitroglycerin at 37 weeks, and then, if unsuccessful, to try again using spinal or epidural anesthesia. Another last ditch idea (on which I could find little information) would be to try to convert breeches at term under epidural anesthesia (with the usual anesthetic level of T5) before doing a cesarean section, and to let the level drop if the version is successful, followed by induction. Although this would require some fine tuning in timing, it might be successful, and only one anesthesia would be needed.
As to the technique, the most important first step is to gently dislodge the breech from the pelvis and then to guide the head downward only after the first step has been accomplished. It does not seem to matter whether the pathway involves a forward roll or a backward roll. Ultrasound should be used to track progress and to observe fetal heart rate changes. Also, versions probably should not be attempted if there is a cord around the neck. Anterior placentas are not a contraindication to EV, but in Rh-negative patients it would be useful to do a post-version Kleihauer-Betke calculation of fetal cells in the maternal circulation to determine if a larger dose of anti-immunoglobulin would be needed.
References
- Hannah ME, et al. Planned cesarean section versus planned vaginal birth for breech presentation at term: A randomised multicentre trial. Term Breech Trial Collaborative Group. Lancet 2000;356:1375-1383.
- Dugoff L, et al. The effect of spinal anesthesia on the success rate of external cephalic version: A randomized trial. Obstet Gynecol 1999;93:345-349.
- Weiniger CF, et al. External cephalic version for breech presentation with or without spinal analgesia in nulliparous women at term: A randomized controlled trial. Obstet Gynecol 2007;110:1343-1350.
- Rozenberg P, et al. External cephalic version with epidural anesthesia after failure of a first trial with beta-mimetics. BJOG 2000;107:406-410.
- Neri I, et al. Acupuncture plus moxibustion to resolve breech presentation: A randomized controlled study. J Matern Fetal Neonatal Med 2004;15:247-252.
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