A randomized controlled trial of intramuscular versus vaginal progesterone for the prevention of recurrent preterm birth

Objective: To compare the efficacy of intramuscular hydroxyprogesterone caproate with that of vaginal progesterone for prevention of recurrent preterm birth. Methods: A prospective randomized controlled trial was conducted at a US tertiary care center between June 1, 2007, and April 30, 2010. Women with singleton pregnancies (16-20 weeks) and a history of spontaneous preterm birth were randomly allocated using a computer-generated randomization sequence to receive either a weekly intramuscular injection of hydroxyprogesterone caproate (250 mg) or a daily vaginal progesterone suppository (100 mg). Participants, investigators, and assessors were not masked to group assignment. The primary outcome was birth before 37 weeks of pregnancy. Per-protocol analyses were performed: participants who completed follow-up were included. Results: Analyses included 66 women given intramuscular progesterone and 79 given vaginal progesterone. Delivery before 37 weeks was recorded among 29 (43.9%) women in the intramuscular progesterone group and 30 (37.9%) in the vaginal progesterone group (P=0.50). Conclusion: Weekly intramuscular administration of hydroxyprogesterone caproate and daily vaginal administration of a progesterone suppository exhibited similar efficacy in reducing the rate of recurrent preterm birth. (C) 2016 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.