Longitudinal Concentrations of Vitamin [B.Sub.12] and Vitamin [B.Sub.12]-Binding Proteins During Uncomplicated Pregnancy (General Clinical Chemistry) (Clinical Report‪)‬

One of the biochemical functions of cobalamin (vitamin [B.sub.12]) in mammals is to maintain normal folate metabolism, which is essential for cell multiplication during pregnancy. Because maternal vitamin [B.sub.12] stores in women eating a mixed diet are ~3000 [micro] and the vitamin [B.sub.12] requirement of the fetus is ~50 [micro], it may be assumed that the event of a single pregnancy has minimal impact on maternal stores (1). On the other hand, vitamin [B.sub.12] deficiency, defined as low serum vitamin [B.sub.12] concentrations, occurs in 10-28% of uncomplicated pregnancies (2). At present little information is available regarding the normal changes in vitamin [B.sub.12] metabolism and concentrations of cobalamin-binding proteins during pregnancy (3). Moreover, much of the reported information (4-6) was collected before the availability of assays for measuring the biologically active form of vitamin [B.sub.12]. No reference values are available for most biochemical indices of vitamin [B.sub.12] status in pregnant women, and often the reference values for nonpregnant individuals are used to assess their vitamin [B.sub.12] status. To our knowledge, no longitudinal studies have been performed to validate the applicability of these reference values for pregnant women.