First-trimester fetal biometry using transvaginal sonography

First-trimester fetal biometry using transvaginal sonography is now feasible and desirable due to improved imaging and probe maneuverability. A study of 144 early normal pregnancies with precise dates is presented. Regression models were constructed for the crown-rump length, biparietal diameter, head circumference and abdominal circumference. Error analysis of the technique and calculations was performed. First-trimester fetal biometry may be used for obtaining precise estimates of gestational age and may help to detect early fetal maldevelopment resulting in abnormal growth.