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. 2019 Oct 3;2019(10):CD013446. doi: 10.1002/14651858.CD013446

Comparison 2. A dose of vitamin D 4000 IU/d or more vs 3999 IU/d or less alone or with any other nutrient.

Outcome or subgroup title No. of studies No. of participants Statistical method Effect size
1 Pre‐eclampsia 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
2 Pre‐eclampsia (by time of commencement of supplementation) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
2.1 Before week 20 of pregnancy 2 1664 Risk Ratio (M‐H, Random, 95% CI) 0.91 [0.65, 1.29]
2.2 At week 20 of pregnancy or later 2 239 Risk Ratio (M‐H, Random, 95% CI) 0.43 [0.11, 1.65]
2.3 Mixed 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
3 Pre‐eclampsia (by frequency of supplementation) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
3.1 Daily 2 1055 Risk Ratio (M‐H, Random, 95% CI) 0.90 [0.59, 1.38]
3.2 Weekly/monthly 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.04, 3.03]
3.3 Bolus dose 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
3.4 Mixed 1 788 Risk Ratio (M‐H, Random, 95% CI) 0.88 [0.49, 1.55]
4 Pre‐eclampsia (by season at the start of supplementation) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
4.1 Summer 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.04, 3.03]
4.2 Fall 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
4.3 Winter 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
4.4 Mixed/unknown 3 1843 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.64, 1.25]
5 Pre‐eclampsia (by registered or not registered) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
5.1 Trial registered 3 1843 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.64, 1.25]
5.2 Trial not registered 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.04, 3.03]
6 Pre‐eclampsia (by impact factor journal) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
6.1 Medium to high 3 1843 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.64, 1.25]
6.2 Low 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.04, 3.03]
7 Pre‐eclampsia (by vitamin D status at baseline) 4 1903 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.62, 1.22]
7.1 Low vitamin D status 1 788 Risk Ratio (M‐H, Random, 95% CI) 0.88 [0.49, 1.55]
7.2 Not low vitamin D status 3 1115 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.58, 1.32]
8 Gestational diabetes 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
9 Gestational diabetes (by time of commencement of supplementation) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
9.1 Before week 20 of pregnancy 2 949 Risk Ratio (M‐H, Random, 95% CI) 0.93 [0.51, 1.69]
9.2 At week 20 of pregnancy or later 2 288 Risk Ratio (M‐H, Random, 95% CI) 0.66 [0.28, 1.55]
9.3 Mixed 1 1039 Risk Ratio (M‐H, Random, 95% CI) 2.00 [0.37, 10.85]
10 Gestational diabetes (by frequency of supplementation) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
10.1 Daily 2 340 Risk Ratio (M‐H, Random, 95% CI) 0.63 [0.34, 1.19]
10.2 Weekly/monthly 1 1039 Risk Ratio (M‐H, Random, 95% CI) 2.00 [0.37, 10.85]
10.3 Bolus dose 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
10.4 Mixed 2 897 Risk Ratio (M‐H, Random, 95% CI) 1.27 [0.58, 2.76]
11 Gestational diabetes (by pre‐pregnancy body mass index) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
11.1 Underweight (lower than 18.5) 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
11.2 Normal weight (18.5 to 24.9) 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
11.3 Overweight (25 or higher) 1 161 Risk Ratio (M‐H, Random, 95% CI) 0.68 [0.28, 1.66]
11.4 Unknown/unreported/mixed 4 2115 Risk Ratio (M‐H, Random, 95% CI) 0.99 [0.57, 1.71]
12 Gestational diabetes (by registered or not registered)n) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
12.1 Trial registered 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
12.2 Trial not registered 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
13 Gestational diabetes (by impact factor journal) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
13.1 Medium to high 4 2167 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.54, 1.39]
13.2 Low 1 109 Risk Ratio (M‐H, Random, 95% CI) 2.95 [0.12, 70.77]
14 Gestational diabetes (by vitamin D status at baseline) 5 2276 Risk Ratio (M‐H, Random, 95% CI) 0.89 [0.56, 1.42]
14.1 Low vitamin D status 1 788 Risk Ratio (M‐H, Random, 95% CI) 1.2 [0.54, 2.68]
14.2 Not low vitamin D status 4 1488 Risk Ratio (M‐H, Random, 95% CI) 0.76 [0.43, 1.36]
15 Preterm birth 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
16 Preterm birth (by time of commencement of supplementation) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
16.1 Before week 20 of pregnancy 3 1825 Risk Ratio (M‐H, Random, 95% CI) 0.80 [0.52, 1.23]
16.2 At week 20 of pregnancy or later 2 84 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.06, 1.94]
16.3 Mixed 1 1039 Risk Ratio (M‐H, Random, 95% CI) 0.92 [0.63, 1.34]
17 Preterm birth (by frequency of supplementation) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
17.1 Daily 2 1037 Risk Ratio (M‐H, Random, 95% CI) 0.70 [0.34, 1.46]
17.2 Weekly/monthly 2 1099 Risk Ratio (M‐H, Random, 95% CI) 0.91 [0.63, 1.32]
17.3 Bolus dose 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
17.4 Mixed 2 812 Risk Ratio (M‐H, Random, 95% CI) 0.82 [0.47, 1.42]
18 Preterm birth (by pre‐pregnancy body mass index) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
18.1 Underweight (lower than 18.5) 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
18.2 Normal weight (18.5 to 24.9) 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
18.3 Overweight (25 or higher) 1 161 Risk Ratio (M‐H, Random, 95% CI) 0.96 [0.41, 2.23]
18.4 Unknown/unreported/mixed 5 2787 Risk Ratio (M‐H, Random, 95% CI) 0.83 [0.62, 1.12]
19 Preterm birth (by season at the start of supplementation) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
19.1 Summer 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.01, 7.87]
19.2 Fall 0 0 Risk Ratio (M‐H, Random, 95% CI) 0.0 [0.0, 0.0]
19.3 Winter 1 24 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.04, 2.77]
19.4 Mixed/unknown 4 2864 Risk Ratio (M‐H, Random, 95% CI) 0.87 [0.65, 1.15]
20 Preterm birth (by registered or not registered) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
20.1 Trial registered 5 2888 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.13]
20.2 Trial not registered 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.01, 7.87]
21 Preterm birth (by impact factor journal) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
21.1 Medium to high 5 2888 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.13]
21.2 Low 1 60 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.01, 7.87]
22 Preterm birth (by vitamin D status at baseline) 6 2948 Risk Ratio (M‐H, Random, 95% CI) 0.85 [0.64, 1.12]
22.1 Low vitamin D status 1 788 Risk Ratio (M‐H, Random, 95% CI) 0.88 [0.49, 1.55]
22.2 Not low vitamin D status 5 2160 Risk Ratio (M‐H, Random, 95% CI) 0.84 [0.61, 1.15]
23 Low birthweight 2 1099 Risk Ratio (M‐H, Random, 95% CI) 0.92 [0.49, 1.70]
24 Fasting glucose levels (mg/dl) 1 113 Mean Difference (IV, Random, 95% CI) ‐2.28 [‐6.18, 1.62]
25 Caesarean section 7 3343 Risk Ratio (M‐H, Random, 95% CI) 1.06 [0.93, 1.20]
26 Maternal death (death while pregnant or within 42 days of termination of pregnancy) 1 1039 Risk Ratio (M‐H, Random, 95% CI) 0.33 [0.01, 8.15]
27 Serum 25‐hydroxyvitamin D concentration at term (in nmol/L) 11 2981 Mean Difference (IV, Random, 95% CI) 31.61 [20.83, 42.38]
28 Gestational hypertension (as defined by trialists) 3 1379 Risk Ratio (M‐H, Random, 95% CI) 1.08 [0.67, 1.74]
29 Birth length (cm) 10 3288 Mean Difference (IV, Random, 95% CI) 0.05 [‐0.26, 0.36]
30 Head circumference at birth (cm) 10 3278 Mean Difference (IV, Random, 95% CI) 0.10 [‐0.09, 0.29]
31 Birthweight (g) 13 3710 Mean Difference (IV, Random, 95% CI) 46.00 [‐8.99, 101.00]
32 Cord blood 25‐hydroxyvitamin D concentration (in nmol/L) 7 2283 Mean Difference (IV, Random, 95% CI) 23.84 [13.55, 34.13]
33 Admission to special care (including intensive care) during the neonatal period (within 28 days after delivery) 1 350 Risk Ratio (M‐H, Random, 95% CI) 1.19 [0.61, 2.32]
34 Stillbirth (as defined by trialists) 4 2882 Risk Ratio (M‐H, Random, 95% CI) 1.37 [0.75, 2.51]
35 Neonatal death (within 28 days after delivery) 3 1939 Risk Ratio (M‐H, Random, 95% CI) 0.99 [0.20, 4.88]