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. ClinicalTrials.gov: NCT00579553.