title: Uptake of cobalamin and markers of cobalamin status: a longitudinal study of healthy pregnant women.
abstract: BACKGROUND
  Currently, it is unknown whether the decline in plasma cobalamin observed during pregnancy is caused by malabsorption of the vitamin. This study examined cobalamin absorption and markers of cobalamin status during normal pregnancy.
  
  
  METHODS
  Twenty-seven pregnant Danish women were examined at gestation weeks 13, 24 and 36. The absorption test CobaSorb was performed in all women implying measurement of holotranscobalamin or cyanocobalamin bound to transcobalamin before and after 2 days intake of 3 × 9 μg cobalamin. Serum cobalamin and the two cobalamin binding proteins transcobalamin and haptocorrin, including haptocorrin saturated with cobalamin or analogues, were measured, and so was plasma methylmalonic acid and homocysteine.
  
  
  RESULTS
  No change in the uptake of cobalamin was observed throughout pregnancy. Serum cobalamin displayed a gradual decline during pregnancy (p<0.0001), while holotranscobalamin remained unchanged, despite an increase in total transcobalamin (p<0.0001). In accord with these results, total haptocorrin showed a decline from the 1st to 3rd trimester (p=0.007) and cobalamin bound to haptocorrin declined (p<0.0001). Interestingly, the amount of cobalamin analogues attached to haptocorrin remained unchanged. Methylmalonic acid (p=0.002) and homocysteine (p<0.0001) increased during pregnancy.
  
  
  CONCLUSIONS
  Cobalamin absorption remains unchanged during normal pregnancy, as judged by the CobaSorb test. No change was observed in the biological active holotranscobalamin during pregnancy. Thus, the pregnancy-related decline in cobalamin is caused by alternations in haptocorrin-bound cobalamin. Surprisingly, no pregnancy-related change was observed in the amount of analogues attached to haptocorrin.
authors.affiliation: Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark. evagreibe@gmail.com
authors.forename: Eva
authors.initials: E
authors.lastname: Greibe
authors.forename: Birgitte Horst
authors.initials: BH
authors.lastname: Andreasen
authors.forename: Dorte L
authors.initials: DL
authors.lastname: Lildballe
authors.forename: Anne L
authors.initials: AL
authors.lastname: Morkbak
authors.forename: Anne-Mette
authors.initials: AM
authors.lastname: Hvas
authors.forename: Ebba
authors.initials: E
authors.lastname: Nexo
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D003718:Denmark; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008137:Longitudinal Studies; D008764:Methylmalonic Acid / Q000097:blood; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood*; D014155:Transcobalamins / Q000032:analysis*; D014805:Vitamin B 12 / Q000097:blood* / Q000493:pharmacokinetics
chemical_list: D015415:Biomarkers; D014155:Transcobalamins; D006710:Homocysteine; D008764:Methylmalonic Acid; D014805:Vitamin B 12