A systematic review and meta-analysis protocol to compare the risk of attrition among prenatal vitamin D supplemented gestational diabetes mellitus patients with its non-recipients

ABSTRACT Aim Recently, several clinical trials have tested the effect of prenatal vitamin D supplementation in gestational diabetes mellitus (GDM) patients and their newborns. However, their participant attrition, an important determinant of the internal validity, remains poorly explored. Therefore, this review protocol is proposed, which aims to compare it between prenatal vitamin D supplemented and not supplemented GDM patients. Method Randomized clinical trials studying the above will be searched mainly in different electronic databases. It will search for the English language articles irrespective of publication date. Data concerning the reviewed trials’ design, population, interventions, and outcome of interest will be extracted. Subsequently, their risk of bias will be assessed. Outcome data between the interventions will be juxtaposed meta-analytically to estimate the risk ratio. Next, the statistical heterogeneity (by Chi 2 and I 2 statistics) and publication bias (using funnel plot and Eggers test) among the trials will be evaluated. Subgroup analysis will follow if the heterogeneity is high. Finally, a sensitivity analysis will iterate the meta-analysis using an alternative model and by eliminating a trial every time. Statistical significance will be determined at p<0.05 and 95% CI. All analyses will be done in Stata. If a meta-analysis is not possible, a narrative reporting will ensue. Results The review will follow the PRISMA reporting guideline. Any statistically significant finding’s evidence quality will be graded by the GRADE approach. Conclusion The proposed review will compare the risk of loss to follow up among GDM patients complemented and not complemented with prenatal vitamin D.