Ultrasonically measured biparietal diameter and abdominal circumference: intra- and interobserver variation in the third trimester.

Serial ultrasound measurements of the fetus under investigation is an important indicator of fetal growth, and thus fetal health. To assess how reliable those measurements are, a videotape was made, and, utilizing an ultrasound machine that allowed the placement of callipers on the videotape, the dispersion of the measurements obtained by 17 sonographers was noted. In the individual fetus in the third trimester of pregnancy, a 95% confidence interval of 3.5 and 2 weeks was found, respectively, for the measurements of the abdominal circumference and biparietal diameter (inter- and intraobserver variation combined).