Baby Due Date from Ultrasound Dating

Often yes in early pregnancy, particularly if you do not know your LMP, have irregular cycles, or your LMP-based dates disagree with CRL measurement. After the first trimester, ultrasound dating becomes less precise for changing the due date.

CRL is the length of the embryo or fetus from crown to rump, measured on ultrasound. In the first trimester it is used to estimate how many weeks pregnant you are and to assign or confirm an estimated due date.

Not usually. Many practices set the EDD from the most reliable early dating scan and keep it unless there is a strong clinical reason to revise it. Later scans track growth but do not constantly move the due date.