Comparison 5.

Vaginal progesterone versus placebo: multiple pregnancy and another risk factor

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Preterm birth less than 34 weeks	2	158	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.29, 1.10]
2 Preterm birth less than 37 weeks	2	168	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.72, 1.18]