The Cobalamin-Binding Proteins Transcobalamin and Haptocorrin in Maternal and Cord Blood Sera at Birth

<jats:title>Abstract</jats:title> <jats:p>Background: Two proteins carry vitamin B12 in plasma. Transcobalamin (TC) carries ∼25% of total plasma vitamin B12 and is 6% to 20% saturated with cobalamin. Haptocorrin (HC) binds ∼80% of total cobalamin and is largely saturated with cobalamin.</jats:p> <jats:p>Methods: We investigated the distribution and the relationship between concentrations of cobalamin, total and holo forms of TC, and HC in blood samples from pregnant women just before delivery (n = 92) and in cord blood samples from their newborn babies. We also investigated the relationship between these proteins and concentrations of methylmalonic acid (MMA), the functional marker of vitamin B12 status.</jats:p> <jats:p>Results: Concentrations of total serum cobalamin, total HC, holoHC, and percentage of HC saturation were higher in cord blood than in the maternal blood (mean cobalamin, 268 vs 188 pmol/L; total HC, 648 vs 538 pmol/L; holoHC, 441 vs 237 pmol/L; HC saturation, 70% vs 47%). Moreover, total TC was low in cord blood, whereas both holoTC and TC saturation were higher in cord blood than in the maternal blood (mean total TC, 654 vs 1002 pmol/L; holoTC, 118 vs 53 pmol/L; TC saturation, 19.8% vs 5.4%). Higher maternal serum cobalamin was associated with higher cord blood holoTC and TC saturation (P &lt;0.05). Gestational age was also a significant determinant of baby total TC, TC saturation, total HC, and holoHC.</jats:p> <jats:p>Conclusion: The close correlation between the amounts of holoTC present in cord blood and in maternal serum supports the importance of maternal cobalamin status for ensuring a sufficient supply to the baby.</jats:p>