If you got a due date from an ultrasound in your sixth, seventh or eighth week, that is the best one to follow. Later in your pregnancy, the baby might grow more quickly or less quickly than average, and by the time you are at your 40th week, due dates given by the baby's measurements can vary by as much as three weeks from the average. Once you have an ultrasound (if it is in your first trimester), if it varies a lot from a due date computed just by counting forward from your last period, go with the one from the ultrasound. Women can ovulate at almost any time, and the time between their last period and their next ovulation can vary. But once the doctor sees and measures the embryo (if it is not late in the pregnancy), that will be the most accurate time to set up a due date estimate.
Idk but I would go off conceived date.