Changes in anthropometric and blood 25-hydroxyvitamin D measurements in antenatal vitamin supplemented gestational diabetes mellitus patients: a systematic review and meta-analysis of randomized controlled trials

Abstract

Objective: Gestation weight (GW), body mass index (BMI), and blood 25-hydroxyvitamin D [25(OH)D] level during pregnancy are important determinants of the gestational outcomes. This study aimed to study how these parameters vary between antenatal vitamin D recipients and non-recipients in gestational diabetes mellitus (GDM) patients.

Material and methods: The randomized controlled trials comparing these outcomes between vitamin D recipient and non-recipient GDM patients were searched in electronic databases (PubMed, Embase, and Scopus). The reviewed studies’ data were abstracted and critically appraised using the Cochrane tool. The estimation of the weighted mean difference for GW and BMI and standardized mean difference (SMD) for 25(OH)D levels occurred by juxtaposing the interventions meta-analytically (random-effect model). The statistical inconsistency was determined by Chi² and I² method. The statistical significance was estimated at p<0.05 and 95% confidence interval (CI).

Results: Eleven eligible trials (all Iran-based, except one), sourcing data from about 875 GDM patients, were reviewed. Overall, the risk of bias was low, except for selection and performance bias. On random-effect model meta-analysis, the 25(OH)D levels of the GDM patients favored the vitamin D recipients when compared to non-vitamin D (SMD 1.97, 95% CI: 1.06-2.88, p<0.001; I² 96.2%, p of Chi² <0.001) and placebo (SMD 1.86, 95% CI: 0.95-2.77, p<0.001; I² 95.3%, p of Chi² <0.001) recipients, respectively. On meta-regression, sample size was a predictor of the observed heterogeneity. For GW and BMI the interventions did not differ statistically significantly.

Conclusion: In GDM patients, antenatal use of vitamin D aids in the rise of blood 25(OH)D levels. However, vitamin D supplementation did not affect change in GW or BMI.

Keywords: Gestational diabetes; dietary supplement; vitamin D,.

Figure 1

Study selection process [PRISMA flow chart (58)]

Figure 2

a) Risk of bias graph: review authors' evaluation of respective risk of bias items presented across all studies included in the review. b) Risk of bias summary: review authors’ evaluation of respective risk of bias item for each included study

Figure 3

Forest plots depicting meta-analysis findings (random-effect model). Outcome: gestational weight a), body mass index b), and 25(OH)D level in blood c). A comparison between antenatal vitamin D supplementation (as the only or cosupplement with other supplements) and non-vitamin D based supplementation; Two trials had with identical trial author name and year have been suffixed with alphabet “a” (50) and “b” (18) after the study name and year SD: Standard deviation, CI: Confidence interval, SMD: Standardized mean difference, 25(OH)D: 25-hydroxyvitamin D

Figure 4

Forest plots depicting meta-analysis findings (random-effect model). Outcome: gestational weight a), body mass index b), and 25(OH)D level in blood c). A comparison between antenatal vitamin D supplementation (as a sole or cosupplement with other supplements) and placebo; Two trials had with identical trial author name and year have been suffixed with alphabet “a” (50) and “b” (18) after the study name and year SD: Standard deviation, CI: Confidence interval, SMD: Standardized mean difference, 25(OH)D: 25-hydroxyvitamin D

Supplemental Figure 1

Forest plot showing meta-analysis comparing between antenatal vitamin D supplementation (as a sole or co-supplement with other supplements) and non-vitamin D supplementation results on 25(OH)D level in blood using random-effect model. Subgroup by sample size (<100 and ≥100 category); Two trials have identical trial author name and year that have been suffixed with alphabet “a” (61) and “b” (27) after the study year SD: Standard deviation, CI: Confidence interval, SMD: Standardized mean difference, 25(OH)D: 25-hydroxyvitamin D

Supplemental Figure 2

Funnel plot assessing publication bias between vitamin D supplemented and not supplemented GDM mothers for 25(OH)D levels in the blood GDM: Gestational diabetes mellitus, SMD: Standardized mean difference, CI: Confidence interval, 25(OH)D: 25-hydroxyvitamin D