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.

Which scan EDD is more accurate?

The earlier the ultrasound is done, the more accurate it is at estimating the babys due date. Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation.

Is dating scan different from LMP?

A dating scan is more accurate. If the scan date differs from your last period dates, the scan date will be used. The scan will usually show that your pregnancy is less far along than suggested by your LMP.