Which is more accurate in late pregnancy: ultrasound or actual gestational age?

In general, during late pregnancy, ultrasound (B超) is more accurate than the actual gestational age based on the last menstrual period; however, combining both methods provides more comprehensive and accurate information. The specific analysis is as follows:

During late pregnancy, pregnant women typically undergo ultrasound examinations to assess fetal growth and development. Ultrasound is a non-invasive method that uses sound waves to generate images of the fetus, helping doctors evaluate fetal size, weight, and organ development. Actual gestational age is usually calculated from the date of the last menstrual period, but its accuracy may be affected by factors such as irregular menstrual cycles or uncertain ovulation dates. Compared with this method, ultrasound tends to be more accurate in late pregnancy. Doctors often combine ultrasound findings with other clinical information—such as the woman’s menstrual history and physical examination—to obtain a more comprehensive assessment of fetal development.

If there is a significant discrepancy between the ultrasound results and the calculated gestational age, doctors may adjust the estimated due date or perform further evaluations. If you experience any discomfort or have additional concerns, consult a healthcare professional for advice.