Vitamin D status and gestational diabetes mellitus

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.

(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.

Tertiary Care Hospital, Antenatal Care Department based prospective, controlled study.

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.

Paired t-test for comparing means, and Fisher's test for comparing proportions.

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).

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.