Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Miscarriage rates
Systematic review	223 women, 93 with 3 or more consecutive miscarriages 4 RCTs in this analysis	Proportion of women who had a miscarriage 23/130 (18%) with progesterone 35/93 (38%) with placebo	Peto OR 0.38 95% CI 0.20 to 0.70 P = 0.002 See further information on studies for details of methodological weaknesses of included RCTs	Moderate effect size	progesterone