This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrics, Subject name: Gynaecology & Obstetrics
A 35-year-old G4P3 at 18 weeks presents with sequential screening( Dual and then triple marker screening) of 1:170 for Down syndrome. You should do which of the following? 
Select and explain. 
A. Offer CVS, B. Advise her the risk is quite small for aneuploidy, C. Perform a targeted ultrasound, D. Offer genetic counseling and perform Amniocentesis
D: Offer genetic counseling and perform Amniocentesis
Answer: D: Offer genetic counseling and perform Amniocentesis 
Explanation: At age 35 should the patient should be offered genetic counseling and Amniocentesis. CVS is not appropriate at 18 weeks' gestation If required; the invasive test of choice here is Amniocentesis.