Kumar 2014.

Methods	Unit of randomization: pregnancy Method of randomization: computer‐generated Timing of randomization: early pregnancy Blinding: yes Power calculation: yes, needed 163 women in each group, planned to recruit 180 women to allow for loss to follow‐up Number of centers: 2 antenatal clinics from one Center 180 women randomized, 826 women had results for primary outcome to analyze Source of funding: Indian Council of Medical Research
Participants	Women with history of idiopathic, ≥ 3 first‐trimester pregnancy losses and currently in the first trimester with a live pregnancy (preferably 2‐8 weeks' gestation). Exclusion: known cause of recurrent miscarriage, women who had taken an injection of hCG or hydroxyprogesterone Age: 18‐35 Location: India
Interventions	20 mg dydrogesterone (taken as 2 x 10 mg tablets) from time of enrolment to 20 weeks Control: identical placebo Additional control group of women without a history of miscarriage who were age‐matched, healthy, pregnant women with at least 1 live birth
Outcomes	Cytokine profiles, pregnancy outcomes (from results section) ‐ miscarriage, EGA at delivery, preterm delivery, cesarean LBW, SGA
Notes	Dates of study: May 2010‐April 2013 Funding sources: Indian Council of Medical Research Declarations of interest: all trial authors state no conflicts of interest
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Simple randomization sequence generated by computers
Allocation concealment (selection bias)	Low risk	Coded numbers on packets each containing 60 tablets of drug or placebo, sequentially distributed
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Randomization unknown until after study completed
Incomplete outcome data (attrition bias) All outcomes	Low risk	12 lost to follow‐up with appropriate reasons
Selective reporting (reporting bias)	Unclear risk	All outcomes recorded not stated in methods
Other bias	Low risk	No other sources of bias identified