My baby will come when it's ready anyway, maybe weeks before or maybe weeks after my due date. These can be carried out from week 5 or 6 of pregnancy, which is a notoriously tricky time to be accurate on dates. Perhaps you are based in the US, or another country, where ultrasound practice is a bit different?
This test is not quite as accurate as the combined test. The nuchal translucency measurement can be taken during the dating scan. Find out more about the combined screening test for Down's syndrome. In the UK, most pregnant women don't have an ultrasound until they are at least 12 weeks pregnant. Well, you'd think so, wouldn't you.