This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in obstetrics, Subject name: Gynaecology & Obstetrics
Karyotyping of fetus can be done through all of the following invasive methods except: 
Select and explain. 
A. Amniocentesis, B. Cordocentesis, C. Chorionic villous sampling, D. fetal skin biopsy
D: fetal skin biopsy
Answer: D: fetal skin biopsy 
Explanation: Invasive methods of prenatal diagnosis: In Chorion villus sampling, Amniocentesis and Cordocentesis fetal cells are obtained for karyotyping.Fetoscopy is done at 16-20 weeks, for visualization of fetal external anatomy and for fetal skin or muscle biopsy for diagnosis of genetic disorders (Meckel-Gruber syndrome). Reference:Dutta,s Textbook of obstetrics 7th edition page no 494