Le Vine 1964.

Methods	Unit of randomization: pregnancy Method of randomization: women were alternated between 'Group A' and 'Group B'. It is unclear who decided which group would be treatment and which would be placebo Timing of randomization: within the 16th week of pregnancy Power calculation: no Blinding: yes (double) Number of centers: not stated 56 women randomized, 26 women excluded, 30 women analyzed Source of funding not stated
Participants	Women who had had 3 consecutive miscarriages, were < 16 weeks' gestation and with no signs of threatened miscarriage in the current pregnancy Age: 20‐42 Location: USA Timing and duration: unknown
Interventions	500 mg/week IM of hydroxyprogesterone caproate Duration: until miscarriage or the 36th week of gestation Control: placebo
Outcomes	Miscarriage Side effects of treatment suffered by the mother Deformities in the baby Preterm birth
Notes	Dates of study: not stated 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	Alternating group A and B
Allocation concealment (selection bias)	High risk	Alternating group A and B
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Stated 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	High risk	56 women randomized, 26 women excluded, 30 women analyzed
Selective reporting (reporting bias)	Low risk	None
Other bias	Low risk	None