Pregnant women of South Asian ethnicity in Canada have substantially lower vitamin B12 status compared with pregnant women of European ethnicity.

Maternal vitamin B-12 (B-12) status has been inversely associated with adverse pregnancy outcomes and positively with fetal growth and infant development. South Asians, Canada's largest ethnic minority, are prone to B-12 deficiency. Yet, data are lacking on B-12 status in South Asian pregnant women in North America. We sought to determine B-12 status, using multiple biomarkers, in 1st and 2nd trimester pregnant women of South Asian and, for comparison, European ethnicity living in Vancouver, Canada. In this retrospective cohort study, total B-12, holotranscobalamin (holoTC), methylmalonic acid (MMA), and total homocysteine concentrations were quantified in two routinely collected (mean gestational week: 11.5 (range 8.3-13.9) and 16.5 (range 14.9-20.9)), banked serum samples of 748 healthy pregnant South Asian (n 371) and European (n 377) women. South Asian pregnant women had significantly lower B-12 status than European pregnant women at both time points, as indicated by lower serum total B-12 and holoTC concentrations, and higher MMA concentrations (all P <= 0.001). The largest difference, which was substantial (Cohen's d >= 0.5), was observed in mean serum total B-12 concentrations (1st trimester: 189 (95 % CI 180, 199) v. 246 (95 % CI 236, 257) pmol/l; 2nd trimester: 176 (95 % CI 168, 185) v. 226 (95 % CI 216, 236) pmol/l). Further, South Asian ethnicity was a significant negative predictor of B-12 status during pregnancy. South Asian women living in Vancouver have substantially lower B-12 status during early pregnancy. Future research identifying predictors and health consequences of this observed difference is needed to allow for targeted interventions.