A randomized double-blind controlled trial of the use of dydrogesterone in women with threatened miscarriage in the first trimester: study protocol for a randomized controlled trial.

Background: Miscarriage is a common complication of pregnancy occurring in 15-20 % of all clinically recognized pregnancies. Currently, there is still no good scientific evidence to support the routine use of progestogens for the treatment of threatened miscarriage because the existing studies were not large enough to show a significant difference and some of them were not randomized or double-blind.

Methods: This is a double-blind, randomized controlled trial. A total of 400 patients presenting with first-trimester threatened miscarriage will be enrolled. They will be randomized to take dydrogesterone 40 mg per os, followed by 10 mg per os three times a day or placebo until twelve completed weeks of gestation or 1 week after the bleeding has stopped, whichever is longer. The primary outcome is the percentage of miscarriage before 20 weeks of gestation.

Discussion: We postulate that the dydrogesterone therapy will significantly reduce the risk of miscarriage in women with threatened miscarriage.

Trial Registration: This study is registered at ClinicalTrials.gov, NCT02128685 . Registered on 29 April 2014.