hi good evening thnxs for your Question' u had history of down baby so u do NT scan with triple marker test at !2 week of your pregnancy. if it normal than risk will be low and finaly do anomalies scan at 20 week . but i suggest do anomalies scan with radiologist for detail anomalies because 90% anomalies can diagnoed with 2D scan . if any Quary mail me on my id itsmedrdarshan@gmail.com

Colur Doppler measures blood flow in the umbilical vein wheras 4 d is seeingvur baby in real time. It's a gimmick. Colour Doppler is useful

Hi, 4D USG detects all structural anomalies while color Doppler detects outrightly vascular problems, and both can be done in one sitting. For down syndrome nuchal translucence, long bone length, major structural defect are to be looked for.