Low plasma vitamin B12 in pregnancy is associated with gestational 'diabesity' and later diabetes

Abstract

Aims/hypothesis: This study was designed to test the hypothesis that low plasma vitamin B12 concentrations combined with high folate concentrations in pregnancy are associated with a higher incidence of gestational diabetes (GDM) and later diabetes. Methods: Women (N=785) attending the antenatal clinics of one hospital in Mysore, India, had their anthropometry, insulin resistance (homeostasis model assessment-2) and glucose tolerance assessed at 30 weeks' gestation (100 g oral glucose tolerance test; Carpenter-Coustan criteria) and at 5 years after delivery (75 g OGTT; WHO, 1999). Gestational vitamin B12 and folate concentrations were measured in stored plasma samples. Results: Low vitamin B12 concentrations (<150 pmol/l, B12 deficiency) were observed in 43% of women and low folate concentrations (<7 nmol/l) in 4%. B 12-deficient women had higher body mass index (p<0.001), sum of skinfold thickness (p<0.001), insulin resistance (p=0.02) and a higher incidence of GDM (8.7% vs 4.6%; OR 2.1, p=0.02; p=0.1 after adjusting for BMI) than non-deficient women. Among B12-deficient women, the incidence of GDM increased with folate concentration (5.4%, 10.5%, 10.9% from lowest to highest tertile, p=0.04; p for interaction=0.2). Vitamin B12 deficiency during pregnancy was positively associated with skinfold thickness, insulin resistance (p<0.05) and diabetes prevalence at 5 year follow-up (p=0.009; p=0.008 after adjusting for BMI). The association with diabetes became non-significant after excluding women with previous GDM (p=0.06). Conclusions/interpretation: Maternal vitamin B12 deficiency is associated with increased adiposity and, in turn, with insulin resistance and GDM. Vitamin B12 deficiency may be an important factor underlying the high risk of 'diabesity' in south Asian Indians. © 2009 Springer-Verlag.