Comparison 6. Low‐dose calcium supplementation (< 1 g/day) with or without co‐supplements vs placebo or no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 High blood pressure (with or without pre‐eclampsia)	5	665	Risk Ratio (M‐H, Fixed, 95% CI)	0.53 [0.38, 0.74]
1.1 Calcium supplementation alone	3	558	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.39, 0.82]
1.2 Calcium plus vitamin D	1	59	Risk Ratio (M‐H, Fixed, 95% CI)	0.65 [0.24, 1.75]
1.3 Calcium plus linoleic acid	1	48	Risk Ratio (M‐H, Fixed, 95% CI)	0.2 [0.05, 0.82]
2 Pre‐eclampsia	9	2234	Risk Ratio (M‐H, Fixed, 95% CI)	0.38 [0.28, 0.52]
2.1 Calcium supplementation alone	4	980	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.23, 0.57]
2.2 Calcium plus vitamin D	2	1060	Risk Ratio (M‐H, Fixed, 95% CI)	0.49 [0.31, 0.78]
2.3 Calcium plus linoleic acid	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.23 [0.09, 0.60]
2.4 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.24 [0.06, 1.01]
3 Preterm birth	6	1290	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.34, 2.03]
3.1 Calcium supplementation alone	1	422	Risk Ratio (M‐H, Random, 95% CI)	0.40 [0.21, 0.75]
3.2 Calcium plus vitamin D	3	760	Risk Ratio (M‐H, Random, 95% CI)	1.59 [1.03, 2.45]
3.3 Calcium plus linoleic acid	1	48	Risk Ratio (M‐H, Random, 95% CI)	0.5 [0.05, 5.15]
3.4 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Random, 95% CI)	0.36 [0.04, 3.23]
4 Admission to neonatal intensive care unit	1	422	Risk Ratio (M‐H, Fixed, 95% CI)	0.44 [0.20, 0.99]
4.1 Calcium supplementation alone	1	422	Risk Ratio (M‐H, Fixed, 95% CI)	0.44 [0.20, 0.99]
4.2 Calcium plus vitamin D	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4.3 Calcium plus linoleic acid	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
5 Stillbirth or death before discharge	5	1025	Risk Ratio (M‐H, Fixed, 95% CI)	0.48 [0.14, 1.67]
5.1 Calcium supplementation alone	1	171	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.07, 16.29]
5.2 Calcium plus vitamin D	1	660	Risk Ratio (M‐H, Fixed, 95% CI)	0.2 [0.01, 4.15]
5.3 Calcium plus linoleic acid	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.6 [0.08, 4.41]
5.4 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.02, 8.39]
6 Placental abruption	3	160	Risk Ratio (M‐H, Fixed, 95% CI)	1.0 [0.14, 6.90]
6.1 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
6.2 Calcium plus vitamin D	2	100	Risk Ratio (M‐H, Fixed, 95% CI)	1.0 [0.14, 6.90]
7 Caesarean section	4	521	Risk Ratio (M‐H, Random, 95% CI)	0.73 [0.46, 1.15]
7.1 Calcium supplementation alone	2	387	Risk Ratio (M‐H, Random, 95% CI)	0.94 [0.40, 2.22]
7.2 Calcium plus vitamin D	0	0	Risk Ratio (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
7.3 Calcium plus linoleic acid	2	134	Risk Ratio (M‐H, Random, 95% CI)	0.55 [0.35, 0.87]
8 Severe pre‐eclampsia	4	246	Risk Ratio (M‐H, Fixed, 95% CI)	0.40 [0.14, 1.15]
8.1 Calcium supplementation alone	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
8.2 Calcium plus vitamin D	2	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.6 [0.08, 4.39]
8.3 Calcium plus linoleic acid	1	86	Risk Ratio (M‐H, Fixed, 95% CI)	0.33 [0.07, 1.56]
8.4 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.04, 3.23]
9 Eclampsia	1	168	Risk Ratio (M‐H, Fixed, 95% CI)	0.17 [0.01, 4.06]
9.1 Calcium supplementation alone	1	168	Risk Ratio (M‐H, Fixed, 95% CI)	0.17 [0.01, 4.06]
9.2 Calcium plus vitamin D	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
9.3 Calcium plus linoleic acid	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
10 Miscarriage	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.06 [0.00, 1.04]
10.1 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	0.06 [0.00, 1.04]
11 Low birthweight (birthweight < 2500 g)	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.2 [0.05, 0.88]
11.1 Calcium supplementation alone	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
11.2 Calcium plus vitamin D	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
11.3 Calcium plus linoleic acid	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.2 [0.05, 0.88]
12 Neonate small‐for‐gestational age	4	854	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.54, 1.21]
12.1 Calcium supplementation alone	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
12.2 Calcium plus vitamin D	1	660	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.58, 1.38]
12.3 Calcium plus linoleic acid	2	134	Risk Ratio (M‐H, Fixed, 95% CI)	0.29 [0.06, 1.32]
12.4 Calcium plus antioxidants	1	60	Risk Ratio (M‐H, Fixed, 95% CI)	1.07 [0.07, 16.31]