I suggest you should go for NIPT at 12 weeks. Rather than going through the proper channel of doing Double marker, and Triple Marker, and Quad Marker is a cumbersome procedure and more expensive than NIPT.  And in your case chances of reaching the NIPT stage are very high. In any case NIPT is (almost) the final court of appeal. You may discuss with your Gynaecologist on this line.

Do NT scan and dual marker at 12 weeks

Wts ur exact gestation age?NT N B scan along with double marker vll help u...u can go for early anomoly scan at 15weeks also

U need to rule out down syndrome

Nt scan 11 to12 weeks ideal Rpt scan once in other scan centre