Hi sir I am 31yrs recently I had a 13 week NT scan which showed a 3mm NT thickness and my doctor suggested to have amniocentesis.i already have a daughter 5yrsold perfectly alright.so my option is to have just a double marker test.if the test is normal then amniocentesis is not needed right?else is it really necessary even if double marker has normal values..pls suggest which option to choose..I know amniocentesis gives complete screening of all abnormalities​ but it has a risk of miscarriage...