Breech presentations (where a baby presents with feet or bottom down) have an increased risk of perinatal and neonatal complications, and are usually delivered by cesarean section. As an alternative, so that the baby can be delivered vaginally, an attempt can be made to turn the baby so that it is head down: this manoeuvre is called an external cephalic version (ECV).

Drugs that relax the uterus (tocolytic agents) are sometimes used to help improve ECV success rates. Nitroglycerin is a tocolytic agent, but intravenous nitroglycerin has not been tested as an agent to help ECV. There is some suggestion that nitroglycerin may be more helpful in women who have not previously been pregnant (nulliparous women) than in women who have been pregnant more than once (multiparous women), and so we have planned two trials.

This study is designed to answer the following questions for nulliparous women:

Will administration of IV nitroglycerin for uterine relaxation improve ECV success rates? Will an increase in ECV success result in a decreased cesarean section rate?

Inclusion Criteria:

• any non-cephalic presentation
• singleton pregnancy
• >/= 37 weeks gestational age
• normal amniotic fluid volume
• reassuring fetal heart rate

Exclusion Criteria:

• labor
• ruptured membranes
• history of third trimester bleeding
• any pre-existing uterine scar
• pregnancy induced hypertension and gestational diabetes
• oligohydramnios and polyhydramnios
• intrauterine growth restriction or macrosomia
• hypotension or any serious medical illness
• inability to comprehend the consent form