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 of the following conditions is not diagnosed by Chorionic Villous Biopsy? 
Select and explain. 
A. Neural tube defects, B. Down's syndrome, C. Phenylketonuria, D. Sickle cell anemia
A: Neural tube defects
Answer: A: Neural tube defects 
Explanation: Chorionic villi are an excellent source of DNA thus apt for genetic techniques. It aids in the prenatal diagnosis of genetic disorders. Chorionic villous sampling is used to detect cytogenetic, biochemical (genetic) or molecular disorders. Neural tube defects are not associated with any of the above and hence not detected by chronic villous biopsy. Ref: Dutta textbook of Obstetrics 6th edition; Page 108