<s>[INST] context: Antiepileptic drugs interfere with metabolism of folate, and patients taking phenytoin may therefore become deficient in folate, leading to the development of macrocytic anemia and possible, complications during pregnancy. Maternal side effects : Nystagmus, Ataxia, Hirsutes, Gingival hyperplasia, Pripheral neurotoxicity, Vit d and Folate deficiency Fetal side effects: Fetal Hydantoin syndrome, Facial clefting, Hea malformations, Limb anomalies, Vit K and D deficiency Possible cognitive effects Folic acid supplements can increase the activity of hepatic microsomal enzymes and thus hasten the clearance of antiepilepsy drugs, leading to a reduced concentration of phenytoin. This situation necessitates the careful monitoring of both folate and phenytoin levels after therapy is initiated. The normal range for folate is 5 to 25 ng/mL. Additionally, phenytoin therapy may increase the metabolism of vitamin D, leading to a decrease in vitamin D levels that can in turn cause alterations in calcium homeostasis that lead to osteomalacia and osteoporosis. Pregnant women taking phenytoin should receive the recommended 400 IU/day of cholecalciferol throughout pregnancy to prevent problems in vitamin D levels and calcium absorption. [/INST] question: Which vitamin deficient is most commonly seen in a pregnant mother who is on phenytoin therapy for epilepsy? | options: A: Vitamin B6 B: Vitamin B12 C: Vitamin A D: Folic acid | answer: D </s>