Use of three-dimensional (3D) sonography to assess the true midsagittal plane of fetal spine.

Objectives: To study the angle of the deviation of a presumed midsagittal plane of the fetal spine from the true midsagittal planes by three-dimensional (3D) ultrasound and to investigate whether the experience of operators has an effect on the degree of this deviation.
Methods: Eight sonographers, four were trained to perform routine anomaly scan (Trained Group) and four were trained to perform fetal biometric measurement only (Non-trained Group), were asked to use a 3D transducer to obtain a 2D image which they thought to represent the true midsagittal plane of the fetal spine. A 3D volume was then acquired. Stored volumes were analyzed using the multiplanar mode. In the transverse plane, the angle of the deviation of presumed midsagittal planes from the true midsagittal planes was measured.
Results: The mean angle of deviation of the trained group was significantly lower than that of the non-trained group (7.9 vs. 21.1, p < 0.001). There were no significant variations among the four operators within each group. However, even among the Trained Group, the angle of deviation could be as large as 27.2°.
Conclusions: Training improved the ability to obtain a midsagittal plane of the fetal spine. 3D ultrasound might provide potential useful information to guide the acquisition of standard image planes.