A Comparison of the Changes in Gestational Weight, Body Mass Index, and Serum Vitamin D Level in Gestational Diabetes Mellitus Patients Complemented with Vitamin D in Contrast to Those Who Did Not Receive the Supplement: A Protocol for Systematic Review and Meta-Analysis of Randomised Controlled Trials

Aims: To date, it is largely unknown how body mass index (BMI), gestational weight (GW), and stored vitamin D (25(OH)D) levels change in the vitamin D-supplemented gestational diabetes mellitus (GDM) patients, irrespective of their pre-pregnancy BMI. Therefore, to study this association, a prospective systematic review and meta-analysis protocol is proposed here. Methods: Primarily, different databases (PubMed, Embase and Scopus) will be searched (without any limitation to date or language) for randomised parallel-arm trials comparing GW, BMI and stored vitamin D level in the body among GDM patients who were supplemented and not supplemented with vitamin D, besides their conventional GDM care. The study selection process and the consecutive risk of bias assessment will adhere to the PRISMA 2009 flow chart and the Cochrane collaboration’s guideline, respectively. These interventions’ effect on the respective outcomes will be compared by meta-analysis (along with an assessment of the statistical heterogeneity) when comparable data will be available from at least 4 studies. Subgroup analysis and Egger’s meta-regression will follow if an adequate number of trials are available. Narrative reporting will be considered when a quantitative comparison is not feasible for any of the outcomes. Conclusion: The proposed review aims to compare the BMI, GW, and 25(OH)D levels in the blood between the vitamin D supplemented and not supplemented GDM patients.