El‐Zibdeh 2005

Methods	Unit of randomization: pregnancy Method of randomization: day of week attending clinic Timing of randomization: presentation for new pregnancy Blinding: unclear Power calculation: no Number of centers: 1 180 women randomized, 0 exclusions, 180 women analyzed Source of funding: not stated
Participants	Women (< 35 years old) with ≥ 3 consecutive unexplained abortions with same husband with a new pregnancy Age: treatment 22% age 20‐24 years, 36% age 25‐29 years, 41.5% age 30‐34 years, control: 21% age 20‐24 years, 48% age 25‐29 years, 31% age 30‐34 years Location: Jordan Timing and duration: 1994‐2000
Interventions	10 mg oral dydrogesterone, twice daily. 5000 IU IM hCG every 4 days, or no treatment Control: no treatment Duration: until miscarriage or 12th gestational week
Outcomes	Miscarriage, preterm delivery, fetal malformations, perinatal death (not analyzed in review: hospitalization for vaginal bleeding)
Notes	Dates of study: 1994‐2000 Funding sources: not stated Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Allocation by day of the week
Allocation concealment (selection bias)	High risk	Allocation by day of the week
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Not stated but unlikely that knowledge of assignment would influence outcomes
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not stated but unlikely that knowledge of assignment would influence outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	Does not appear to be incomplete data
Selective reporting (reporting bias)	Low risk	None noted
Other bias	Low risk	None noted