IRCT20120718010324N59 IRCT 2020-11-04 Tabriz University of Medical Sciences The effect of Vitamin D on fasting plasma glucose and Insulin levels The Effect of Vitamin D on Insulin Resistance Biomarker and Fasting Blood Glucose in Pregnant Women: A Randomized Controlled Trial. 2020-11-21 anticipated 88 Complete https://irct.ir/trial/50973 interventional Randomization: Randomized, Blinding: Triple blinded, Placebo: Used, Assignment: Parallel, Purpose: Treatment, Randomization description: Participants in the study will be assigned to two groups (one group receiving 4,000 units of oral vitamin D daily and one group receiving placebo with the same protocol) by stratified block randomization method (stratification based on deficient or insufficient serum levels of vitamin D) with block sizes of 4 and 6 and a allocation ratio of 1: 1 and using the website www.random.org . To hide the Allocation (Allocation Concealment), the allocation sequence will be identified by a person not involved in the study using a randomizer, and the 4,000-unit drug and placebo will be placed in the same packages numbered sequentially, Blinding description: The participants, researcher and data analyst will be blinded completely in this study. Drug and placebo will be similar in appearance (shape, color, smell) and packaging of drug and placebo will be conducted by a person not involved in the research. 3 Gestational Diabetes. Intervention 1: The intervention group will receive 4000 units of oral vitamin D daily produced by Dana Pharmaceutical Company, which is quite similar in appearance to the drug used in the placebo group. This intervention will last for 17 weeks. Intervention 2: The control group will receive an oral placebo daily produced by Dana Pharmaceutical Company, which in terms of appearance is quite similar to the drug used in the intervention group. This study will last for 17 weeks. No - There is not a plan to make this available Justification or reason for not sharing IPD is Participant data is confidential.