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 a 20 week ultrasound be wrong?

While gender prediction is much more accurate during the 20-week ultrasound, theres still a chance it can be wrong.

Can a dating scan be wrong by 4 weeks?

It is very common when scanning an early pregnancy to find that the due date does not match the menstrual history. Sometimes the dates can be more than a week off and sometimes even as much as 4 weeks.

Can ultrasound detect abnormalities baby?

What can an ultrasound tell about a baby? Ultrasound can detect some types of physical birth defects. Examples of physical birth defects that may be found at 19 - 20 weeks are most cases of spina bifida, some serious heart defects, some kidney problems, absence of part of a limb and some cases of cleft palate.