“If dating is only based on the last menstrual period and a later ultrasound shows a discrepancy, then the due date may be changed,” Lamppa says. If your due date is confirmed by an ultrasound in the first trimester, it shouldnt change as the pregnancy progresses, even with additional ultrasounds, she says.

Are scans accurate with due date?

Determining a Due Date Evidence suggests that ultrasounds more accurately predict your due date than using your last menstrual period—but only in the first trimester and early second trimester (until roughly 20 weeks). 3 Early ultrasound due dates have a margin of error of roughly 1.2 weeks.

Can your due date change at 12 week scan?

In early pregnancy, your due date can be predicted using the first day of your last period (LMP) by adding 280 days. However, once you have a 12 week (dating) scan then the date is determined from that scan onwards.

Can a baby hide on an ultrasound?

Ultrasound can tell us a lot about a pregnancy, but its not always perfect. This is particularly true in the early months of pregnancy. Though it is rare, it is possible to have a hidden twin that is not visible during early ultrasound screenings.