How accurate is an Ultrasound when done at 14 weeks?
I’m assuming you mean accurate in terms of dating your pregnancy. In that case then you are right, that the farther along you are the less accurate it is in determining how far along you are, since genetics play a part in your baby’s body type. When you have an early ultrsound it’s very accurate, within a week of dating the pregnancy, later on it can be off by weeks. If your first ultrasound matches with your LMP, they will not change your due date based off a later ultrasound.