Abstract: Vitamin B12 is one of the most important microelements in the body, the amount needed of which can be taken from food. As a coenzyme, vitamin B12 participates in a series of celluar reactions. In mammals, for example, it is involved in the synthesis and metabolism of homocysteine and methylmalonic acid and multi-system dysfunctions will happen when they accumulate in human body. When it is insufficient, multi-system dysfunctions will happen. In gestation period, enhanced protein biosynthesis and mitochondrial energy conversion increases the requisite amount of vitamin B12. Due to the increased requirement of it, vitamin B12 is more prone to suffer from deficiency. Absencing of vitamin B12, during gestation period, has implications including hypertensive disorder complicating pregnancy, intrahepatic cholestasis of pregnancy etc. Furthermore neonate methylmalonic acidemia, fetal intrauterine growth restriction and other diseases will be arised.

Key words: Vitamin B12, Vitamin B12 deficiency, Hyperhomocysteinemia, Hypertension, pregnancy-induced, Cholestasis, intrahepatic