Comparison 3. Routine high‐dose calcium supplementation in pregnancy by study sample size.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 High blood pressure (with or without proteinuria)	12	15470	Risk Ratio (M‐H, Random, 95% CI)	0.65 [0.53, 0.81]
1.1 Studies with < 400 participants	7	675	Risk Ratio (M‐H, Random, 95% CI)	0.38 [0.21, 0.68]
1.2 Studies with =/> 400 participants	5	14795	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.70, 0.98]
2 Pre‐eclampsia	13	15730	Risk Ratio (M‐H, Random, 95% CI)	0.45 [0.31, 0.65]
2.1 Studies with < 400 participants	8	935	Risk Ratio (M‐H, Random, 95% CI)	0.21 [0.12, 0.36]
2.2 Studies with =/> 400 participants	5	14795	Risk Ratio (M‐H, Random, 95% CI)	0.71 [0.52, 0.97]
3 Preterm birth	11	15275	Risk Ratio (M‐H, Random, 95% CI)	0.76 [0.60, 0.97]
3.1 Studies with < 400 participants	6	810	Risk Ratio (M‐H, Random, 95% CI)	0.43 [0.24, 0.76]
3.2 Studies with =/> 400 participants	5	14465	Risk Ratio (M‐H, Random, 95% CI)	0.86 [0.69, 1.07]
4 Admission to neonatal intensive care unit	4	13406	Risk Ratio (M‐H, Fixed, 95% CI)	1.05 [0.94, 1.18]
4.1 Studies with < 400 participants	1	63	Risk Ratio (M‐H, Fixed, 95% CI)	0.29 [0.03, 2.48]
4.2 Studies with =/> 400 participants	3	13343	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.94, 1.19]
5 Stillbirth or death before discharge from hospital	11	15665	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.74, 1.09]
5.1 Studies with < 400 participants	6	846	Risk Ratio (M‐H, Fixed, 95% CI)	0.39 [0.02, 9.20]
5.2 Studies with =/> 400 participants	5	14819	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.74, 1.09]