Comparison 1. Strict bed rest in hospital versus no activity restriction at home.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Very preterm birth (less than 34 weeks) ‐ assuming complete correlation between twins/triplets	5	495	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.66, 1.58]
2 Perinatal mortality	5		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
2.1 Assuming independence between twins/triplets	5	1016	Risk Ratio (M‐H, Fixed, 95% CI)	0.65 [0.35, 1.21]
2.2 Assuming complete correlation between twins/triplets	5	495	Risk Ratio (M‐H, Fixed, 95% CI)	0.70 [0.30, 1.63]
3 Low birthweight (less than 2500 g)	3		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
3.1 Assuming independence between twins/triplets	3	502	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.75, 1.21]
3.2 Assuming complete correlation between twins/triplets	3	238	Risk Ratio (M‐H, Random, 95% CI)	0.91 [0.74, 1.11]
4 Low birthweight (less than 2500 g) ‐ subgroup analysis	3		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
4.1 Twin pregnancy	1	424	Risk Ratio (M‐H, Random, 95% CI)	0.84 [0.66, 1.07]
4.2 Triple pregnancy	2	78	Risk Ratio (M‐H, Random, 95% CI)	1.09 [0.64, 1.86]
5 Prelabour preterm rupture of the membrane	3	276	Risk Ratio (M‐H, Fixed, 95% CI)	1.30 [0.71, 2.38]
6 Spontaneous onset of labour	4	488	Risk Ratio (M‐H, Fixed, 95% CI)	1.05 [1.02, 1.09]
7 Caesarean delivery	4	283	Risk Ratio (M‐H, Fixed, 95% CI)	0.69 [0.41, 1.17]
8 Development of maternal hypertension	5	495	Risk Ratio (M‐H, Fixed, 95% CI)	0.68 [0.37, 1.23]
9 Stillbirth (after 20 weeks and before birth)	5		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
9.1 Assuming independence between twins/triplets	5	1016	Risk Ratio (M‐H, Random, 95% CI)	0.78 [0.20, 2.98]
9.2 Assuming complete correlation between twins/triplets	5	495	Risk Ratio (M‐H, Random, 95% CI)	0.81 [0.25, 2.69]
10 Early neonatal death (within 7 days after birth)	5		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
10.1 Assuming independence between twins/triplets	5	1016	Risk Ratio (M‐H, Fixed, 95% CI)	0.72 [0.28, 1.87]
10.2 Assuming complete correlation between twins/triplets	5	495	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.27, 2.74]
11 Preterm birth (less than 37 weeks) ‐ assuming complete correlation between twins/triplets	5	495	Risk Ratio (M‐H, Random, 95% CI)	0.97 [0.80, 1.18]
12 Birthweight (g)	3	314	Mean Difference (IV, Fixed, 95% CI)	136.99 [39.92, 234.06]
13 Very low birthweight (less than 1500 g)	2		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
13.1 Assuming independence between twins/triplets	2	445	Risk Ratio (M‐H, Random, 95% CI)	1.32 [0.15, 11.70]
13.2 Assuming complete correlation between twins/triplets	2	219	Risk Ratio (M‐H, Random, 95% CI)	1.64 [0.31, 8.70]
14 Gestational age at delivery (weeks)	5	495	Mean Difference (IV, Fixed, 95% CI)	‐0.14 [‐0.51, 0.24]
15 Small‐for‐gestational age	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
15.1 Assuming independence between twins/triplets	2	293	Risk Ratio (M‐H, Fixed, 95% CI)	0.75 [0.56, 1.01]
15.2 Assuming complete correlation between twins/triplets	2	137	Risk Ratio (M‐H, Fixed, 95% CI)	0.71 [0.46, 1.10]
16 Apgar score less than 7 (at 5 minutes)	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
16.1 Assuming independence between twins/triplets	2	299	Risk Ratio (M‐H, Fixed, 95% CI)	1.60 [0.55, 4.62]
16.2 Assuming complete correlation between twins/triplets	2	146	Risk Ratio (M‐H, Fixed, 95% CI)	1.35 [0.34, 5.32]
17 Admission to neonatal intensive care unit	3		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
17.1 Assuming independence between twins/triplets	3	571	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.74, 1.06]
17.2 Assuming complete correlation between twins/triplets	3	276	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.68, 1.14]