Comparison 2.

Vaginal progesterone versus no treatment or placebo

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Preterm birth less than 34 weeks	6	1727	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.63, 1.09]
2 Preterm birth less than 34 weeks subgroup by dose	6	1727	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.64, 1.07]
2.1 Low dose (200 mg or less daily)	4	1267	Risk Ratio (M‐H, Random, 95% CI)	0.93 [0.63, 1.37]
2.2 High dose (more than 200 mg daily)	3	460	Risk Ratio (M‐H, Random, 95% CI)	0.68 [0.52, 0.90]
3 Preterm birth less than 34 weeks subgroup by timing	6	1727	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.63, 1.09]
3.1 Starting before 20 weeks' gestation	1	91	Risk Ratio (M‐H, Random, 95% CI)	0.69 [0.30, 1.58]
3.2 Starting after 20 weeks' gestation	4	1256	Risk Ratio (M‐H, Random, 95% CI)	0.74 [0.60, 0.91]
3.3 Mixed timing of start	1	380	Risk Ratio (M‐H, Random, 95% CI)	1.35 [0.90, 2.02]
4 Perinatal death	3	2287	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [0.74, 2.06]
5 Perinatal death subgroup by dose	3	2287	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [0.74, 2.06]
5.1 Low dose (200 mg or less daily)	3	2287	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [0.74, 2.06]
6 Perinatal death subgroup by timing	3	2287	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [0.74, 2.06]
6.1 Starting before 20 weeks' gestation	1	171	Risk Ratio (M‐H, Fixed, 95% CI)	1.98 [0.18, 21.39]
6.2 Starting after 20 weeks' gestation	1	1346	Risk Ratio (M‐H, Fixed, 95% CI)	1.11 [0.51, 2.42]
6.3 Mixed timing of start	1	770	Risk Ratio (M‐H, Fixed, 95% CI)	1.29 [0.63, 2.61]
7 Prelabour rupture of the membranes	2	514	Risk Ratio (M‐H, Fixed, 95% CI)	0.61 [0.23, 1.60]
8 Preterm birth less than 37 weeks	6	1597	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.89, 1.06]
9 Preterm birth less than 28 weeks	4	1569	Risk Ratio (M‐H, Fixed, 95% CI)	1.22 [0.68, 2.21]
10 Adverse drug reaction	2	562	Risk Ratio (M‐H, Fixed, 95% CI)	0.99 [0.90, 1.09]
11 Caesarean section	6	2143	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.88, 0.98]
12 Satisfaction with therapy	1	494	Mean Difference (IV, Fixed, 95% CI)	0.0 [‐0.35, 0.35]
13 Antenatal tocolysis	4	1420	Risk Ratio (M‐H, Fixed, 95% CI)	0.80 [0.62, 1.02]
14 Antenatal corticosteroids	4	1422	Risk Ratio (M‐H, Fixed, 95% CI)	0.87 [0.71, 1.06]
15 Infant birthweight less than 2500 g	4	3079	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.88, 1.03]
16 Apgar score < 7 at 5 minutes	3	2410	Risk Ratio (M‐H, Fixed, 95% CI)	0.65 [0.35, 1.19]
17 Respiratory distress syndrome	4	2560	Risk Ratio (M‐H, Random, 95% CI)	0.84 [0.64, 1.10]
18 Use of mechanical ventilation	5	3134	Risk Ratio (M‐H, Fixed, 95% CI)	0.61 [0.48, 0.77]
19 Intraventricular haemorrhage ‐ all grades	1	1333	Risk Ratio (M‐H, Fixed, 95% CI)	1.70 [0.62, 4.66]
20 Retinopathy of prematurity	2	1945	Risk Ratio (M‐H, Fixed, 95% CI)	1.07 [0.45, 2.54]
21 Necrotising enterocolitis	3	2117	Risk Ratio (M‐H, Fixed, 95% CI)	0.52 [0.13, 2.06]
22 Neonatal sepsis	2	1944	Risk Ratio (M‐H, Fixed, 95% CI)	1.41 [0.86, 2.33]
23 Fetal death	3	2328	Risk Ratio (M‐H, Fixed, 95% CI)	1.38 [0.65, 2.90]
24 Neonatal death	3	2905	Risk Ratio (M‐H, Fixed, 95% CI)	1.53 [0.75, 3.15]
25 Admission to NICU	5	4052	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.87, 1.00]
26 Patent ductus arteriosus	2	1946	Risk Ratio (M‐H, Fixed, 95% CI)	0.76 [0.47, 1.22]
27 Sensitivity analysis for perinatal death (assuming total non‐independence)	3	1144	Risk Ratio (M‐H, Fixed, 95% CI)	1.22 [0.61, 2.44]
28 Sensitivity analysis for perinatal death (assuming 1% non‐independence)	3	2263	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [0.74, 2.06]