You may refer to the link https://www.google.com.sg/amp/s/sg.theasianparent.com/list-of-scans-during-pregnancy/amp for a better understanding of different scans throughout your pregnancy.
Its up to you. We went for a clear piece of mind..
If u are under pvt den yes each visit will just be a normal scan.. unless they schedule you for detailed scan or growth scan den tht will be a much more thorough scan..a Downsyndrome scan is more like to give u an early heads up so u can decide fr yr next step.. if u have already decided that no matter what you will keep your baby, den u cn skip the test. All the best!
Sharlene