The earlier in pregnancy a scan is performed, the more accurate the age assignment from crown rump length 4. If the original CRL measurement was adequate, the measurement is considered the baseline for all subsequent age measurements.

When do you use crown rump length?

Crown-rump length may be used to accurately date pregnancy between 7 and 13 weeks gestation. The technique involves measurement of the fetal length from the tip of the cephalic pole to the tip of the caudal pole.

Why is crown rump length most accurate?

Crown rump length (CRL) is the length of the embryo or fetus from the top of its head to bottom of torso. It is the most accurate estimation of gestational age in early pregnancy, because there is little biological variability at that time.