Maintenance Therapy by Vaginal Progesterone after Threatened Idiopathic Preterm Labor: A Randomized Placebo-Controlled Double-blind Trial

Abstract

Background: Patients with arrested preterm labor (PTL) are at increased risk for recurrence ofpreterm birth (PTB). Maintenance tocolysis after arrest of acute PTL is of questionable value. Theobjective of this study was to evaluate the efficacy of 200 mg vaginal progesterone in order toprevent PTB in women with episodes of threatened PTL.Materials and Methods: This is a randomized double blind clinical trial study.Women with singletonpregnancies between 28-36 weeks of gestation, who were hospitalized for PTL were included. Atotal of 173 pregnant patients were randomly allocated to receive 200 mg vaginal progesteronesuppositories (n=86) or placebo (n=87) daily until the 36th gestational week. The two groups werecompared relative to demographic characteristics, incidence of PTB before 34 and 37 weeks, andmaternal and neonatal complications. Data were analyzed by chi-square and Fisher’s exact tests.Results: Mean latency until delivery in the cases was longer than the control group (23.88 ± 18.01vs. 16.67 ± 12.9; p=0.004).Treatment with progesterone was not associated with a reduction inthe rate of PTB before 34 weeks [cases: 9 (10.8%) vs. controls: 8 (10%)] and 37 weeks [cases: 45(54.2%) vs. controls: 33 (41.2%)]. Log rank analysis revealed a significant difference for mean timeto delivery between the two groups (p=0.028). There were no significant differences for neonataland maternal complications in the two groups.Conclusion: Prophylactic administration of 200 mg vaginal progesterone suppositories aftersuccessful tocolysis in patients with threatened idiopathic PTL is associated with a longer latencyto delivery, but failed to reduce the rate of PTB (Registeration Number: IRCT138706051096N1).