Fetal biometry by an inexperienced operator using two- and three-dimensional ultrasound

Objective: To compare the reproducibility, accuracy and time required for fetal biometric measurements using two-dimensional (2D) and three-dimensional (3D) ultrasonography by an inexperienced operator.

Methods: Fifty consecutive fetuses were evaluated at a gestational age of 17-34 weeks. For every fetus measurements-including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL)-were made by an inexperienced operator using 2D ultrasound and then saved 3D volumes. As a control, measurements were also made by an experienced operator using 2D ultrasonography alone. Each fetal biometric parameter was measured twice by each operator. All images were assessed by two experienced reviewers, blinded to the operator's identity, using a scoring system based on objective evaluation criteria.

Results: The interobserver, intraobserver and inter- method variability for 2D ultrasonography by the experienced operator (2D-exp), and 2D and 3D ultrasonography by the inexperienced operator (2D-inexp and 3D-inexp) was small (all intraclass correlation coefficients > or = 0.991). A non-significantly higher proportion of fetal biometric measurements by 3D-inexp than 2D-inexp were within 1 mm of the measurements by 2D-exp. There were no differences in the mean image quality scores of fetal biometry between 2D-exp and 2D-inexp, 2D-exp and 3D-inexp. However, the quality score of AC images obtained by 3D-inexp was greater than that obtained by 2D-inexp (5.5 vs. 5.3, P = 0.018). The mean time required to measure BPD, HC, AC and FL was less for 3D-inexp than for 2D-inexp (67.2 vs. 97.0 s, 64.6 vs. 97.0 s, 60.1 vs. 81.5 s and 65.5 vs. 95.1 s, respectively; all P < 0.001), but was significantly greater than for 2D-exp, with corresponding figures of 24.3, 24.3, 27.9 and 27.2 s.

Conclusion: Fetal biometric measurements obtained by an inexperienced operator using both 2D and 3D ultrasound were reproducible and showed good agreement with those obtained by an experienced operator. The use of 3D ultrasound by an inexperienced operator allows faster measurements to be made than by 2D ultrasound and also seems to facilitate the acquisition of higher-quality images for measurement of AC.