Nifedipine Versus Magnesium Sulfate for Late Early Preterm Tocolysifs (ASTOS2)

Nifedipine Versus Magnesium Sulfate for Tocolysis in Pregnant Women at 32 - 36 Weeks Gestation With Threatened Preterm Labor

Objective: This trial is designed to compare between the effectiveness of nifedipine versus magnesium sulfate (MgSO4) for tocolysis in women with threatened preterm labor. Patient Population: The population will include pregnant women at gestational age between 32 and 36 weeks who are 18 years old or older and have signs of threatened preterm labor. Study Design: This is a single-center, prospective, randomized controlled clinical trial. A total of 264 women pregnant between 32 and 36 weeks having threatened preterm labor will be enrolled and randomized into two parallel treatment arms. Patients in the group A will receive nifedipine, while patients in group B will MgSO4 only. Treatment: All patients will be randomized on the day of enrollment. Patients with threatened preterm labor will receive the respective tocolysis in each group. All patients will receive corticosteroids for lung maturity according to the local protocol. Primary outcome: Number of women not delivered within 48 hours of starting tocolytic therapy. Secondary outcomes: perinatal mortality, a composite of adverse neonatal outcomes, birth weight, days on ventilation support, length of admission in neonatal intensive care, prolongation of pregnancy more than 7 days, delivery after 37 weeks of gestation, number of days till delivery, maternal mortality, maternal infection, and harm to mother from intervention.

The initial dose of nifedipine will be 2 × 10 mg nifedipine capsules orally in the first hour, followed by 20 mg slow-release nifedipine every 6 hours for the next 47 hours. In the first hour after starting nifedipine, blood pressure and heart rate will be measured every 15 minutes. If blood pressure remains within the normal limits, treatment will be continued.

Women will receive only MgSo4. A loading dose of MgSo4 will be given immediately after enrollment as 4 gm diluted in 200 mL of saline solution administered intravenous over a period of 20 minutes. Afterwards, the maintenance dose of MgSo4 will be administered intravenous in a dose of 1 gm/hour given as 6 gm diluted in 500 mL saline solution titrated with a rate of 100 mL per hour, then this dose is repeated every 6 hours for 48 hours. Respiratory rate and knee jerk will be assessed hourly for women in the MgSo4 group. Serum magnesium level will be measured if clinically indicated.

The initial dose of nifedipine will be 2 × 10 mg nifedipine capsules orally in the first hour, followed by 20 mg slow-release nifedipine every 6 hours for the next 47 hours. In the first hour after starting nifedipine, blood pressure and heart rate will be measured every 15 minutes. If blood pressure remains within the normal limits, treatment will be continued.

Women will receive only MgSo4. A loading dose of MgSo4 will be given immediately after enrollment as 4 gm diluted in 200 mL of saline solution administered intravenous over a period of 20 minutes. Afterwards, the maintenance dose of MgSo4 will be administered intravenous in a dose of 1 gm/hour given as 6 gm diluted in 500 mL saline solution titrated with a rate of 100 mL per hour, then this dose is repeated every 6 hours for 48 hours. Respiratory rate and knee jerk will be assessed hourly for women in the MgSo4 group. Serum magnesium level will be measured if clinically indicated.

postponing delivery for at least 48 hours to allow the time for corticosteroid administration for fatal lung maturity

admission to intensive care, anaphylactic shock, dyspnoea, hypotension (leading to cardiotocography abnormalities), liver test abnormalities (elevated aspartate aminotransferase (AST) or alanine aminotransferase (ALT)), general side effects (nausea, vomiting, headache) and postpartum haemorrhage defined as >500 mL blood loss

Inclusion Criteria: Pregnant women with threatened preterm labor defined as 3 or more uterine contractions in 30 minutes confirmed by cardiotocography. Gestational age from 32 week + 0 days to (inclusive) 36 weeks + 0 days. Women with singleton or multiple pregnancy. Women with preterm prelabor rupture of membranes (PROM) will be included if they have uterine contractions. Exclusion Criteria: Contraindications for the use of either drugs, such as cardiac disease, hypotension, myasthenia gravis, or renal impairment. Contraindications for tocolysis, such as intrauterine demise, intrauterine infection, fetal distress, placental separation, or severe pre-eclampsia. Cervical dilatation > 5 cm. Cervical length > 30 mm by trans-vaginal ultrasound. Cervical cerclage.