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 is the investigation of choice in a pregnant lady at 18 weeks of pregnancy with past history of delivering a baby with Down's syndrome : 
Select and explain. 
A. Triple screen test, B. Amniocentesis, C. Chorionic villous biopsy, D. Ultrasonography
B: Amniocentesis
Answer: B: Amniocentesis 
Explanation: Ans. is b i.e. Amniocentesis In a pregnant lady with H/0 previous Down syndrome, the chances of recurrence are increased. Extensive screening should be carried out in all such females. Now in the question given - female is presenting at 18 weeks and investigation of choice is being asked which will definately be amniocentesis. At 18 weeks Screening test : quad test I Triple test. Investigation of choice : Amniocentesis. In first trimester (or 1st screening test Combined test Investigation of choice chorionic villi sampling. Screening test selectior Women presenting to ANC clinic before 14 weeks. Nuchan translucency + free phCG +PAPP-A (k/a combined test) Based on result if