Vitamin B12 maintains normal folate metabolism which is essential for cell multiplication during pregnancy. No good data are available on what constitutes vitamin B12 deficiency in pregnancy, nevertheless vitamin B12 deficiency is frequently reported in pregnancy due to inadequate dietary intake of vitamin B12 and a physiological decline of maternal vitamin B12 concentrations. This decline can be explained by the increased maternal metabolic rate and active transport by the placenta to the fetus. If the mother is deficient during pregnancy, the baby may have low serum vitamin B12 concentrations at birth [1]. Vitamin B12 deficiency during pregnancy is associated with preeclampsia, fetal growth restriction, preterm labor, neural tube defects, neonatal megaloblastic anemia and neonatal neurological symptoms. It has been suggested to improve vitamin B12 status of women in the periconceptional period by supplementation of vitamin B12, but no randomized studies on the outcome of such supplementation have been published.