Nifedipine for Acute Tocolysis of Preterm Labor

Inclusion Criteria:

- Between 16 and 44 years of age inclusive

- Singleton pregnancy

- Intact membranes

- Between 28-0/7 weeks and 33-6/7 weeks' gestation inclusive

- Reported or documented uterine activity

- Cervical dilation between 2 cm and 4 cm inclusive

Exclusion Criteria:

- Multifetal gestation

- Less than 28 weeks' gestation

- 34 or more weeks' gestation

- Ruptured membranes

- More than 4 cm dilated

- Previously received a course of corticosteroids for fetal lung maturation

- Oligohydramnios

- Fetal growth restriction

- Chorioamnionitis or temperature of at least 38.0 degrees Celsius

- Fetal death

- Preeclampsia

- Suspected placental abruption or placenta previa

- Lethal fetal malformation or amniotic fluid index at least 35

- Systolic BP < 90 mmHg or diastolic BP < 50 mmHg

- Baseline tachycardia (pulse >120 after 2 consecutive measurements 30 minutes apart)

- Chronic hypertension treated with antihypertensives in pregnancy

- Seizure disorder or HIV

- Maternal allergy to nifedipine

- Known maternal cardiac disease

- Women who have received progesterone therapy in the second or third trimester for
prevention of preterm birth