Pregnant women of South Asian ethnicity in Canada have substantially lower vitamin B₁₂status compared with pregnant women of European ethnicity

Abstract

Maternal vitamin B12 (B12) 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 B12 deficiency. Yet, data are lacking on B12 status in South Asian pregnant women in North America. We sought to determine B12 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 B12, 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 B12 status than European pregnant women at both time points, as indicated by lower serum total B12 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 B12 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 B12 status during pregnancy. South Asian women living in Vancouver have substantially lower B12 status during early pregnancy. Future research identifying predictors and health consequences of this observed difference is needed to allow for targeted interventions.

High incidence of maternal vitamin B12 deficiency detected by newborn screening: first results from a study for the evaluation of 26 additional target disorders for the German newborn screening panel

“…In accordance with this MMA and Hcy levels have been reported to increase by late pregnancy [32,33]. A Canadian study found that 10% of women are vitamin B 12 deficient in early pregnancy [34], and several consecutive studies have confirmed similar findings or even higher frequencies for vitamin B 12 deficiency in pregnancy of up to 30% in different populations and ethnicities [31,[35][36][37][38]. This underscores the relevance of this condition for NBS programmes and stresses that also in caregivers of pregnant women awareness for B 12 deficiency should be increased.…”

The Many Faces of Cobalamin (Vitamin B12) Deficiency

“…Wnt signaling has been reported to be disrupted in the developing cerebellum of the offspring of vitamin B 12 – and folate-deficient female rats 78 and is associated with long-term disabilities of behavior and memory 79 . Ethnic differences in vitamin B 12 levels have been observed in pregnancy, possibly related to differences in intake of animal-derived foods 80 . Children born to mothers with normal to high folate levels and low serum vitamin B 12 values have higher truncal adiposity and insulin resistance, 81 which may influence long-term risk of development of type 2 diabetes and cardiovascular disease 82, 83.…”

Approaches to improving micronutrient status assessment at the population level

“…Consideration of ethnicity as an effect modifier in biomarker concentration and potential risk marker should be carefully evaluated. In our work on maternal micronutrient status in pregnant women of South Asian ethnicity residing in British Columbia, Canada, we showed that women of South Asian ethnicity have substantially lower vitamin B 12 status, as shown by the significantly lower serum total B 12 and holotranscobalamin concentration and higher serum MMA concentration, compared with women of European ethnicity in early pregnancy ( 53 ) . There was no significant difference in tHcy concentration between the two ethnic groups; however, this can likely be explained by the high folate status in Canadian pregnant women including our cohort with a median serum folate concentration of about 65 nmol/l ( 53 ) and with folate being the main determinant of tHcy concentration ( 56 ) .…”

“…With respect to the routinely applied biomarker serum total vitamin B 12 and related cut-off, there is a general concern that the rate of B 12 deficiency is overestimated during pregnancy because of a natural decrease in serum total B 12 concentrations across trimesters of pregnancy ( 52 – 54 ) , potentially attributable to pregnancy-related haemodilution, changes in glomerular filtration rate, and the preferential unidirectional transport of nutrients to the developing fetus. Also serum holotranscobalamin, the biomarker reflecting the portion of vitamin B 12 available to tissues and alternative direct B 12 indicator, significantly decreased between first and second trimester of pregnancy ( 53 ) , while the functional biomarker plasma MMA increased between the first and second ( 53 ) , and between second and third trimester ( 55 ) . As for cut-offs for all other age and population groups, a defined clinical and/or physiologic endpoint is required to validate cut-offs for the reliable definition of maternal vitamin B 12 adequacy and thereby for achieving both maternal health and optimal fetal growth and development.…”