<prompt> A 35 year old female with a previous history of bih of a child with Downs syndrome, presents with 18 weeks Amenorrhoea. The Investigation of choice rule out Downs syndrome in the present pregnancy is:Triple testAmniocentesisCordocentesisChorionic villous biopsy  <response>: The Answer is B Amniocentesis : At 18 weeks of pregnancy the best confirmatory test available is amniocentesis Triple test only gives a risk ratio. For confirmation of diagnosis, amniocentesis has to be done - Dutta 