Most women can instead have their first scan at 11 to 13 weeks — this is usually called the 12-week scan. This scan can work out the due date and gestational age of the baby, if youre having more than one baby and also screen for conditions like Down syndrome.

Are scan dates from conception or LMP?

Because few women know the exact day they ovulated or conceived, an ultrasound done in the first trimester of pregnancy has been shown to the be the most accurate way to date a pregnancy. If an ultrasound date in the first trimester differs from your LMP date by seven days or more, we would go with the ultrasound.