A comparison of standard two-dimensional ultrasound to three-dimensional volume sonography for routine second-trimester fetal imaging

OBJECTIVE: In comparison with standard two-dimensional (2D) imaging of fetal structure and biometry, we aimed to evaluate the role of three-dimensional (3D) imaging as a screening tool in the mid-trimester. STUDY DESIGN: Pregnant women presenting between 18and 22 weeks for routine anatomical survey and biometric measurements were recruited. Six volumes of fetal anatomic regions were obtained and archived for later reconstruction, along with three volumes of extra-fetal structures (placenta, cervix, amniotic fluid). The 2D standard fetal images were then obtained. Offline reconstruction of 3D volumes was performed for comparative analysis (2D vs 3D). Subsequently, 3D volumes were reconstructed to mirror traditional 2D and allow biometric comparison between the two techniques. Data of 98 patients were analyzed. RESULTS: Complete visualization of vital anatomic structures was seen >= 85% of the time with 3D ultrasound. The 3D imaging improved the assessment of the four heart chambers (P=0.003), thoracic spine (P=0.008) and lumbar spine (P=0.012) views. The 2D imaging was superior for the fetal head, placenta and upper limbs. Conditional probabilities were used to assess the clinical value of 3D when standard 2D views were incomplete (mean 0.8830; 95% confidence interval 0.8059 to 0.9320). Overall diagnostic accuracy of 3D ultrasound is not superior for all fetal anatomic structures. Fetal biometric measurements assessed by both techniques demonstrated substantial to excellent agreement. CONCLUSION: The use of 3D imaging as a primary screening tool is limited and may be best utilized as a second-stage test. Overall, there is good correlation between fetal biometry assessed by either 2D or 3D technology.