Czajkowski 2007.

Methods	2‐arm active‐controlled randomised trial
Participants	53 women were randomised in a hospital setting in Poland. The population comprised women with signs and symptoms of threatened abortion (vaginal bleeding usually accompanied by abdominal pains), live singleton intrauterine pregnancy confirmed by ultrasound examination, and gestational age of 12 weeks. Exclusion criteria comprised women with a history of hypertension, diabetes mellitus, severe liver disorders (i.e. Rotor syndrome, Dubin‐Johnson syndrome, jaundice, or liver failure), drug or alcohol addiction, uterine anomalies, cervical disease, cerebral apoplexy, and allergy to any component of the drugs that would be administered in the study. Women who had received any hormonal drug during the last 3 weeks preceding the study or had participated any other clinical trial during the last 3 months were also excluded.
Interventions	300 mg micronized vaginal progesterone daily plus oral placebo versus 30 mg of oral dydrogesterone daily plus vaginal placebo for 6 weeks.
Outcomes	The study recorded the following outcomes relevant for this review: miscarriage.
Notes	Evidence of trial documentation and data requested from the corresponding author, but no response was received by the time of publication of this review.