Vitamin B12 Status in a Cohort of Canadian Pregnant Women and Newborn Infants

Abstract

Low maternal concentrations of vitamin B12 (B12) adversely affect fetal development. In Canada, low serum B12 concentrations (<148 pmol/L) are prevalent among women of reproductive age. We measured concentrations of serum B12 and its functional biomarkers, plasma total homocysteine (tHcy) and methylmalonic acid (MMA), in 368 pregnant women at 12‐16 wk gestation, at delivery and in cord blood. We also determined the effect of major fetal genetic variants of B12 metabolism on cord plasma concentrations of B12, tHcy and MMA. The prevalence of low serum B12 concentrations at recruitment and delivery was 17% and 37%, respectively. Elevated plasma MMA concentrations (>270 nmol/L) were only observed in 2% and 5% of women at recruitment and delivery, respectively, and no women had plasma tHcy concentrations >13 μmol/L. During pregnancy, mean serum B12 concentrations decreased by 23%, while plasma tHcy and MMA increased by 20% and 24%, respectively (p<0.0001). Mean cord blood concentrations of B12, tHcy and MMA were 1.9, 0.8 and 2.3 times maternal concentrations at delivery (p<0.0001). Cord plasma MMA concentrations were significantly altered by the MTR rs1805087, MUT rs1141321 and MMAA rs2270655 genotypes (p<0.04), while cord serum B12 and plasma tHcy concentrations were altered by the TCN1 rs34324219 genotype (p=0.04). Our data suggest that although “suboptimal” serum B12 levels are prevalent in Canadian pregnant women, they are unlikely functionally significant as evidenced by MMA and tHcy status. Fetal genetic variants appear to influence cord blood concentrations of B12, MMA and tHcy. Funded by CIHR MOP#106446