Maternal and foetal nutritional requirements are exceptionally high during pregnancy to meet the associated physiological and metabolic demands. The estimated intake requirements during lactation were based on the loss of cobalamin in milk or milk cobalamin content. Pregnancy associated haemodilution, enhanced renal function and hormonal changes lead to reduced concentrations in many blood biomarkers during pregnancy. Pregnancy-related anaemia is common in many parts of the world where micronutrient deficiencies are common. Megaloblastic anaemia in pregnancy has been attributed to folate deficiency since the discovery of folate in 1948 and the famous studies on folate deficient Indian women who developed severe anaemia in pregnancy. Low pregnancy serum cobalamin has also been associated with low birth weight. In women with no apparent cobalamin deficiency, recent cobalamin intake or the amount of the vitamin that is absorbed appears to be more important than maternal stores as a determinant of milk cobalamin.