The aim of the study is evaluating the associations of FokI vitamin D receptor 
(VDR) gene polymorphisms with gestational diabetes mellitus (GDM), and its 
relations with postpartum metabolic syndrome. In a cohort study, 303 women 
referred to outpatient clinic of Shariati Hospital. The VDR FokI genotypes were 
determined. All subjects were followed 6?12 weeks after delivery. The 
frequencies of Ff, FF, and ff genotypes were 30.4% (49), 63.4% (102), and 6.2% 
(10), respectively, in healthy pregnancies and 34.5% (49), 54.9% (78), and 10.6% 
(15), respectively, in GDM patients. The ff genotype was more common in GDM 
patients. Healthy individuals had higher frequency of F allele, suggesting that 
F allele may have a role in decreased incidence of GDM. Concerning the GDM risk 
factors, f allele had significant association with prepregnancy obesity and 
family history of diabetes. In postpartum follow-up, women who developed 
metabolic syndrome were significantly older with higher prepregnancy body mass 
index, had more family history of diabetes, and also their ff genotype was two 
fold more frequent. Our results indicate a meaningful association between FokI 
VDR genotypes and an increase risk of GDM in Iranian population as well as its 
effects on postpartum metabolic syndrome.