Comparison 2. Heparin + aspirin versus aspirin.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Live birth	5	1295	Risk Ratio (M‐H, Random, 95% CI)	1.27 [1.09, 1.49]
2.1.1 UFH + aspirin versus aspirin	2	140	Risk Ratio (M‐H, Random, 95% CI)	1.74 [1.28, 2.35]
2.1.2 LMWH + aspirin versus aspirin	3	1155	Risk Ratio (M‐H, Random, 95% CI)	1.20 [1.04, 1.38]
2.2 Pre‐eclampsia	2	82	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.10, 3.14]
2.3 Adverse events in the mother	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
2.3.1 Bleeding	1	31	Risk Ratio (M‐H, Fixed, 95% CI)	1.65 [0.19, 14.03]
2.3.2 Heparin‐induced thrombocytopenia	2	140	Risk Ratio (M‐H, Fixed, 95% CI)	Not estimable
2.3.3 Allergic reactions	1	90	Risk Ratio (M‐H, Fixed, 95% CI)	Not estimable
2.4 Venous thromboembolism	3	182	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
2.5 Arterial thromboembolism	3	182	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
2.6 Preterm delivery of a live infant	3	156	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.42, 2.07]
2.7 Intrauterine growth restriction	3	151	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.33, 2.19]
2.8 Adverse events in the child	1	51	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
2.8.1 Congenital malformations	1	51	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
2.9 Pregnancy loss	5	1295	Risk Ratio (M‐H, Random, 95% CI)	0.48 [0.32, 0.71]
2.9.1 UFH + aspirin versus aspirin	2	140	Risk Ratio (M‐H, Random, 95% CI)	0.46 [0.29, 0.71]
2.9.2 LMWH + aspirin versus aspirin	3	1155	Risk Ratio (M‐H, Random, 95% CI)	0.55 [0.26, 1.16]