Which vitamin deficiency is most commonly seen in a pregnant mother who is on phenytoin therapy for epilepsy?

Phenytoin inhibits the enzyme intestinal conjugase, an impoant enzyme in folic A. Metabolism. Folate is present in food in a polyglutamate form. This is conveed into monoglutamates by intestinal conjugase to be absorbed in the jejunum. Phenytoin acts by inhibiting this enzyme thereby causing folate deficiency and thus megaloblastic anemia.