Comparison 1. Progestogens versus placebo or no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Miscarriage	7	696	Risk Ratio (M‐H, Fixed, 95% CI)	0.64 [0.47, 0.87]
1.1 Oral progestogen versus no treatment	3	408	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.38, 0.85]
1.2 Vaginal progesterone versus placebo	4	288	Risk Ratio (M‐H, Fixed, 95% CI)	0.75 [0.47, 1.21]
2 Preterm birth	5	588	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.52, 1.44]
3 Pregnancy‐induced hypertension	2	337	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.54, 1.88]
4 Antepartum haemorrhage	2	337	Risk Ratio (M‐H, Fixed, 95% CI)	0.76 [0.30, 1.94]
5 Stillbirth	2	262	Risk Ratio (M‐H, Fixed, 95% CI)	1.94 [0.18, 20.49]
6 Congential abnormalities	2	337	Risk Ratio (M‐H, Fixed, 95% CI)	0.70 [0.10, 4.82]