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: Pathology
A 12 week anomaly scan of 29 year old lady,revealed foetal malformation. On fuher investigation it was found she had taken some vitamin supplements. Which of the following is most likely to be responsible for the foetal defects? 
Select and explain. 
A. Vit A, B. Vit B, C. Vit E, D. Vit C
A: Vit A
Answer: A: Vit A 
Explanation: Retinoic acid is a known human teratogen. There is extreme susceptibility for teratogenicity in 3rd to 9th week. Retinoic acid causes changes in HOX gene expression. Note: Valproate also cause disruption of HOX gene expression. Ref: Robbins Basic Pathology, Edition 8, Page 256