Goldzieher 1964.

Methods	Unit of randomization: pregnancy Method of randomization: sequentially numbered bottles. It is not clear who was responsible for the coding. Timing of randomization: unclear Blinding: yes (double) Power calculation: no Number of centers: 2 main centers 54 women randomized, 0 women excluded, 54 women analyzed Source of funding: Upjohn
Participants	Women who had either: never had a term pregnancy and who had had ≥ 2 miscarriages; or who had had ≥ 1 term pregnancy followed by a minimum number of 2 consecutive miscarriages. All women had to have a urinary pregnanediol of < 5 mg/d before 8 weeks' gestation and/or < 7 mg/d by 14 weeks' gestation. Age: not stated Location: USA
Interventions	10 mg/d of oral medroxyprogesterone Control: placebo Duration: not stated
Outcomes	Miscarriage Preterm delivery
Notes	Dates of study: not stated Funding sources: supported by a grant from the Upjohn Company, Kalamazoo, Michigan Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Low risk	Sequentially numbered bottles. Code not broken until end of trial
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind
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 outcome data
Selective reporting (reporting bias)	Low risk	None
Other bias	Low risk	None apparent