Study to Evaluate is ECV Success is Improved and the Side Effects Reduced With the Use of IV NTGL Versus Terbutaline

Breech presentation of a term pregnancy is a common occurrence. A procedure known as external cephalic version (ECV) is frequently used by obstetricians to turn the baby into the vertex position prior to delivery in order to avoid a cesarean section and the associated risks. Medications to relax the uterus, known as tocolytics, are used in conjunction with the procedure as they have been shown to improve the success rate of ECV, but with inconsistent, varying results.

Breech presentation occurs in approximately 3-4% of all births and all women with breech presentation at term undergo cesarean delivery. The only way to avoid a cesarean is to manually turn the baby prior to the date of delivery, a procedure known as elective external cephalic version (ECV). ECV has been shown to reduce the frequency of breech presentation at term and thus lessen the risks associated with breech delivery and those of cesarean section, with little risk to the mother or baby. Tocolysis, administered immediately prior to the ECV and commonly used at The Mount Sinai Hospital, has been shown to improve the success rate of ECV. Several different agents are known to cause tocolysis. These include beta-mimetics (ritodrine, terbutaline), nitroglycerine (NTGL) and nifedipine.Terbutaline has been shown to improve success rate of ECV. Another study published in 2004 by El-Sayed et al showed that subcutaneous terbutaline was associated with higher rates of successful ECV than IV NTGL in term patients. There is inconsistent data in regard to the success rate of ECV with NTGL. In a study published in 2003 by Bujold et al, NTGL was associated with a higher rate of side effects and a lower rate of successful ECV when compared to ritodrine. Another study published in 2009 by Hilton et al showed that NTGL was more efficacious for ECV in nulliparous versus multiparous women. Yet another study published in 2009 by Yanny et al showed no differences between sublingual NTGL versus placebo in efficacy, and reported no significant side effects. A study published in 2003 by Bujold et al showed that sublingual NTGL was associated with a higher incidence of headache and did not improve the success rate of ECV. It may be beneficial to use NTGL instead of terbutaline because NTGL is a shorter acting agent and the procedure itself only lasts 10-15 minutes. Additionally, both medications have side effects. Terbutaline is associated with maternal tachycardia, hyperglycemia, hypokalemia, pulmonary edema, cardiac arrhythmias, hypertension and myocardial ischemia, and NTGL is associated with maternal nausea, vomiting, headache, and hypotension. For both medications the side effects are self- limiting but depending on the patient's co-morbidities one drug may be beneficial for that individual patient. To date no study has compared the efficacy of intravenous terbutaline versus intravenous NTGL in women presenting for ECV. The purpose of this study is to determine if the success rate of ECV can be improved with the use of IV NTGL.