Table 3.
Summary of meta-analyses of randomized controlled trials on vitamin D in pregnancy in relation to maternal health.
| Outcomes | First author | Year | No. of studies in MA | Comparator (vitamin D supplementation or level) | Effects model | Metric of MA | Effect size | 95% CI | I2 (%) | Publication bias |
|---|---|---|---|---|---|---|---|---|---|---|
| Preterm birth | Liu | 2022 | 27 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | RR | 0.938 | (0.790 ~ 1.090) | 9 | NA |
| Preterm birth | Wu | 2023 | 10 | high dose (≥ 400 IU/day) vs placebo | fixed-effect | OR | 0.37 | (0.22 ~ 0.62)* | 0 | NA |
| Preterm birth | Irwinda | 2022 | 6 | dose≤ 2000 IU/day vs placebo | random-effect | OR | 0.84 | (0.46 ~ 1.53) | 42 | NA |
| Preterm birth | Irwinda | 2022 | 10 | high dose (> 2000 IU/day) vs low dose (≤ 2000 IU/day) | random-effect | OR | 1.01 | (0.82 ~ 1.26) | 0 | NA |
| Pre-eclampsia | Irwinda | 2022 | 3 | dose ≤ 2000 (IU/day) vs placebo | random-effect | OR | 0.29 | (0.09 ~ 0.95)* | 0 | NA |
| Pre-eclampsia | Irwinda | 2022 | 8 | high dose (> 2000 IU/day) vs low dose (≤2000 IU/day) | random-effect | OR | 0.8 | (0.51 ~ 1.24) | 31 | NA |
| Gestational diabetes mellitus | Irwinda | 2022 | 2 | dose ⩽ 2000 IU/day vs placebo | random-effect | OR | 0.92 | (0.59 ~ 1.42) | 0 | |
| Gestational diabetes mellitus | Irwinda | 2022 | 7 | high dose (> 2000 IU/day) vs low dose (≤2000 IU/day) | random-effect | OR | 0.7 | (0.51 ~ 0.95)* | 0 | NA |
| 25(OH)D | Wu | 2023 | 9 | high dose (≥400 IU/day) vs placebo | random-effect | SMD | 4.07 | (2.73 ~ 5.41)* | 97 | NA |
| 25(OH)D | Motamed | 2022 | 15 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | 2.07 | (1.51 ~ 2.63)* | 94 | <0.001 |
| 25(OH)D on cord blood | Motamed | 2022 | 3 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | 1.13 | (-0.28 ~ 2.54) | 96 | 0.77 |
| Total cholesterol | Wu | 2023 | 7 | high dose (≥ 400 IU/day) vs placebo | random-effect | SMD | (-0.67) | (-1.19 ~ -0.14)* | 85 | NA |
| Low-density lipoprotein cholesterol | Wu | 2023 | 7 | high dose (≥ 400 IU/day) vs placebo | fixed-effect | SMD | (-0.49) | (-0.68 ~ -0.29)* | 30 | NA |
| Triglycerides | Wu | 2023 | 6 | high dose (≥ 400 IU/day) vs placebo | random-effect | SMD | (-0.59) | (-1.01 ~ -0.17)* | 77 | NA |
| High-density lipoprotein cholesterol | Wu | 2023 | 8 | high dose (≥ 400 IU/day) vs placebo | fixed-effect | SMD | 0.41 | (0.23 ~ 0.58)* | 0 | NA |
| Caesarean section | Wang | 2021 | 9 | supplement vs placebo or nothing | fixed-effect | RR | 0.75 | (0.63 ~ 0.89)* | 43 | NA |
| Hospitalization | Wang | 2021 | 2 | supplement vs placebo or nothing | fixed-effect | RR | 0.13 | (0.02 ~ 0.98)* | 0 | NA |
| Postpartum hemorrhage | Wang | 2021 | 2 | supplement vs placebo or nothing | fixed-effect | RR | 0.47 | (0.22 ~ 1.00) | 0 | NA |
| Hyperbilirubinemia | Wu | 2023 | 9 | high dose (≥ 400 IU/day) vs placebo | fixed-effect | OR | 0.38 | (0.25 ~ 0.58)* | 0 | NA |
| hs-CRP | Motamed | 2022 | 10 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | 0.24 | (-0.56 ~ 1.04) | 95 | 0.22 |
| Total antioxidant capacity | Motamed | 2022 | 9 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | 2.13 | (1.04 ~ 3.23)* | 97 | <0.001 |
| Malondialdehyde | Motamed | 2022 | 6 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | (-0.46) | (-0.87 ~ -0.05)* | 75 | 0.003 |
| Glutathione | Motamed | 2022 | 9 | high dose (> 400 IU/day) vs low dose (≤ 400 IU/day) or placebo | random-effect | SMD | 4.37 | (2.90 ~ 5.84)* | 98 | <0.001 |
MA meta-analysis, RR relative risk, OR odds ratio, SMD standardized mean difference, NA not available, * significant difference, 25(OH)D 25-hydroxyvitamin D, hs-CRP high sensitivityC-reactive protein.