Background: Sonographic estimation of birth weight may differ among evaluators due to its operator-dependent nature.

Objectives: To compare the accuracy of estimation of fetal birth weight by sonography between ultrasound-certified physicians and registered diagnostic medical technicians.

Methods: The authors reviewed ultrasound examinations that had been performed by either technicians or ultrasound-certified obstetricians between 2010 and 2017, and within 2 days of delivery. Inclusion criteria were: singleton viable pregnancy, details of four ultrasound measurements (abdominal circumference, bi-parietal diameter, head circumference, and femur length), and known birth weight. The estimated fetal weight (EFW) was calculated according to the Hadlock formula, incorporating the four ultrasound measurements. The mean percentage error (MPE) was calculated by the formula: (EFW-birth weight) x100 / birth weight.

Results: Technicians performed 9741examinations and physicians performed 352 examinations. The proportion of macrosomic neonates was similar in both groups. Technicians were more accurate than physicians in terms of the MPE, absolute MPE, proportion of estimates that fell within ± 10% of birth weight, and Euclidean distance (P < 0.0001 for all comparisons). They were also more accurate in terms of sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating curve. Furthermore, for fetuses weighing more than 4000 grams the technicians had a lower total false prediction rate.

Conclusions: Medical technicians in our institute performed better than physicians in estimating fetal weight. Further studies are warranted to confirm our findings and better delineate the role of repeat physician’s examination after an initial estimation by an experienced technician.