Vitamin D status and gestational diabetes mellitus

CONTEXT: Vitamin D (Vit D) deficiency and gestational diabetes mellitus (GDM) are increasingly being seen in Indian women. The role of Vit D in causing GDM is not clear. AIMS: (1) To compare Vit D status in pregnant women with or without GDM. (2) Frequency of GDM in women with Vit D insufficiency and deficiency. (3) To reassess glucose tolerance after replacement of Vit D in those women with Vit D deficiency and GDM. SETTINGS AND DESIGN: Tertiary Care Hospital, Antenatal Care Department based prospective, controlled study. SUBJECTS AND METHODS: Seventy-eight consecutive women (<28 weeks gestational period) were screened for GDM by glucose tolerance test (GTT) (75 g 2 h). Fifty-nine of these women were confirmed to have GDM (2 h postglucose > 140 mg/dl). Eight of these women were excluded as per laid exclusion criteria. Remaining 19 women with normal glucose tolerance (NGT) were included as controls. Serum 25-OH Vit D level was estimated by radioimmuno assay. Standard advice regarding diet, sunlight exposure, and exercise was given to all by the same dietician. Women with Vit D levels below 20 ng/ml were prescribed 60,000 IU of oral cholecalciferol to be administered twice weekly for 4 weeks. GTT was repeated after 6 weeks. Frequency of glucose intolerance was compared between Vit D sufficient and deficient groups. Women with GDM and Vit D deficiency who revert to NGT after supplementation with cholecalciferol were evaluated. STATISTICAL ANALYSIS USED: Paired t-test for comparing means, and Fisher's test for comparing proportions. RESULTS: Baseline characteristics of GDM and NGT with respect to their age, prepregnancy body mass index, and gestational period were comparable. Serum 25-OH Vit D levels were significantly lower in GDM 24.7 (±17.6) ng/ml versus NGT (45.8 ± 28) group (P = 0.0004). Frequency of GDM was similar irrespective of Vit D status 67% versus 42% (P = 0.09). Standard advice on diet and exercise with or without Vit D supplementation did not significantly differ in the conversion of GDM to NGT (P = 0.63). CONCLUSION: Although Vit D deficiency is associated with GDM however its replacement does not reverse the glucose intolerance. There is no justification at present for routine screening for Vit D deficiency or its replacement in the management of GDM.