Effect of vitamin D supplementation on insulin resistance and inflammatory factors in women with gestational diabetes

The aim of this study is to determine the effects of vitamin D supplementation on insulin resistance, inflammatory factor and biomarkers of oxidative stress in gestational diabetes.

Double-blind randomized controlled clinical trial

Among patients with gestational diabetes mellitus referred to maternity Clinic affiliated to Kashan University of Medical Sciences, Kashan, Iran, 54 patients will be selected according to inclusion and exclusion criteria.

Inclusion criteria are including, pregnant women aged 18-40 years diagnosed with GDM at 24-28 weeks gestation. In addition, exclusion criteria are including, those with premature preterm rupture of membrane, placenta abruption, or preeclampsia; those who required commencing insulin therapy during intervention; those with hypothyroidism or urinary tract infection; those who smoked; those with kidney or liver diseases; and those taking estrogen therapy.

Intervention group: Vitamin D supplements (Zahravi Pharm Company, Iran), 50000 IU, every 3 weeks for 6 weeks orally. Control group: Placebo supplements (Barij Essence, Kashan, Iran), every 3 weeks for 6 weeks orally

Serum levels of 25-hydroxyvitamin D (primary outcome), Fasting plasma glucose (FPG), serum insulin, insulin resistance, inflammatory factor and biomarkers of oxidative stress (secondary outcomes)

Kashan University of Medical Sciences

To decrease potential confounding effects, all participants will have stratified randomization according to BMI and weeks of gestation. Then, participants in each block will be randomly allocated into two treatment groups to take either vitamin D supplement or placebo. Randomization will be done by the use of Stat Trek software. Participants, investigators or the assessors of the outcomes are also unaware of the study groups. https://stattrek.com/statistics/random-number-generator.aspx

Randomization and allocation will be concealed from the researchers and participants until the final analyses are completed. Another person at the maternity clinics affiliated with Kashan University of Medical Sciences, who is not involved in the trial and not aware of random sequences, will be assigned the participants to the numbered bottles of capsules. Supplements and placebo are in the same packaging at the Barij Essence pharmaceutical company. Only the code is written on the packages. Patients and researcher do not know the type of drug and after analyzing the data, packet codes are decoded.