Tocolytic Therapy for Preterm Labor in Multiple Gestation

To compare the tocolytic efficacy oxytocin receptor antagonist (Atosiban) with that of calcium channel blockers (Nifedipine) among women with multiple gestation who present with threatened preterm labor.

Preterm birth remains the principal cause of early neonatal death. Infants born preterm (before 37 weeks' gestation) often suffer significant immediate morbidity and need lengthy stays in neonatal intensive care units. Moreover, there is a significant risk of long-term neurological morbidity in a proportion of the survivors. Patients with a multiple gestation are at significant risk for preterm labor and delivery as approximately 60% of all those pregnancies will be delivered preterm. A number of oxytocin receptor antagonists have been developed, and of these, three, atosiban, barusiban and retosiban have been investigated in humans as tocolytic agents. To date, only atosiban is in use outside of clinical trials. Atosiban is an oxytocin receptor antagonist which was specifically developed for the treatment of preterm labor. Early reports of the use of Atosiban for tocolysis showed promise both in vitro and in animal studies, and preliminary studies in pregnant and non-pregnant humans suggested a very low incidence of maternal side effects .

Women with twin pregnancy with preterm labor between 24 weeks 0 days and 32 weeks 6 days of gestation will be included and randomly assigned to the Atosiban group.

Women with twin pregnancy with preterm labor between 24 weeks 0 days and 32 weeks 6 days of gestation will be included and randomly assigned to the Nifedipine group.

After random allocation to a treatment group, women will receive Atosiban as follows: Atosiban was given as a single loading intravenous dose, 6.75 mg in 0.9% sodium chloride solution, followed by an intravenous infusion of 300 micrograms/min in 0.9% sodium chloride solution for the first 3 hours and then 100 micrograms/min for another 45 hours. The choice of the dose regimen for Atosiban was consistent with the recommendations of the product labeling.

After random allocation to a treatment group, women will receive Nifedipine as follows: Nifedipine was given as a loading dose of 20 mg orally followed by another two doses of 20 mg, 20-30 minutes apart as needed. Maintenance was started after 6 hours with 20-40 mg four times a day for a total of 48 hours.

Inclusion Criteria: Twin pregnancy Gestational age between 24+0 and 32+6 weeks Intact amniotic membranes Threatened preterm labor Age 18-50. Exclusion Criteria: Rupture of membranes Vaginal bleeding resulting from placenta previa or placental abruption Fever above 38°C Severe preeclampsia Maternal cardiovascular or liver diseases Systolic blood pressure less than 90 mm Hg Known uterine malformation Intrauterine growth restriction below the fifth percentile Non-reassuring fetal status Antepartum diagnosis of major fetal malformations Fetal death Previous tocolytic therapy or Betamethasone treatment

Wilson A, Hodgetts-Morton VA, Marson EJ, Markland AD, Larkai E, Papadopoulou A, Coomarasamy A, Tobias A, Chou D, Oladapo OT, Price MJ, Morris K, Gallos ID. Tocolytics for delaying preterm birth: a network meta-analysis (0924). Cochrane Database Syst Rev. 2022 Aug 10;8(8):CD014978. doi: 10.1002/14651858.CD014978.pub2.