This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Which vitamin deficiency is most commonly seen in a pregnant mother who is on phenytoin therapy for epilepsy: 
Select and explain. 
A. Vitamin B6, B. Vitamin B12, C. Vitamin A, D. Folic acid
D: Folic acid
Answer: D: Folic acid 
Explanation: Hypotension and arrythmias occur only on iv injection.
Vitamin deficiencies associated with phenytoin: — Folic acid (most common)

– Vitamin D
– Vitamin K
These vitamin deficiencies occur in all patients an phenytoin therapy and have nothing do with pregnancy. Hence all patients on phenytoin are advised to take folic acid supplementation.