OBJECTIVE:

To estimate whether treatment with intravenous nitroglycerin for uterine relaxation increases the chance of successful external cephalic version.

METHODS:

Two double-blind, randomized clinical trials were undertaken: one in nulliparous women and a second in multiparous women. Women presenting for external cephalic version at term were eligible to participate. The primary outcome was immediate success of external cephalic version. Other outcomes were presentation at delivery, cesarean delivery rate, and side effects and complications. Sample size calculations were based on a 100% increase in success of external cephalic version with a one-sided analysis and alpha=0.05 (80% power).

RESULT:

In total, 126 women were recruited-82 in the nulliparous trial and 44 in the multiparous trial. Seven patients did not have external cephalic version before delivery but were included in the analysis of success of external cephalic version. One patient was lost to follow-up. The external cephalic version success rate for nulliparous patients was 24% (10 of 42) in patients who received nitroglycerin compared with 8% (3 of 40) in those who receive placebo (P=.04, one-sided Fisher exact test, odds ratio 3.85, lower bound 1.22). In multiparous patients, the external cephalic version success rate did not differ significantly between groups: 44% (10 of 23) in the nitroglycerin group compared with 43% (9 of 21) in the placebo group (P=.60).

CONCLUSION:

Treatment with intravenous nitroglycerin increased the rate of successful external cephalic version in nulliparous, but not in multiparous, women. Treatment with intravenous nitroglycerin appeared to be safe, but our numbers were too small to rule out rare serious adverse effects.

LEVEL OF EVIDENCE:

I.