Sonographic Assessment of Fetal Anatomy in the First Trimester: A Comparative Study of Visualization Rates Using Two-...

Background/Objectives: This study aimed to compare the visualization rates of fetal anatomical structures with standard 2D ultrasound examination versus a single 3D volume acquired during the first trimester. Methods: This multicenter prospective study was performed in nine tertiary referral centers, by experienced sonographers. A standard protocol was adopted in both 2D and 3D modalities to assess the 17 anatomical structures listed in the national and international guidelines. The included cases were non-anomalous fetuses from women booked for combined screening test between 11 + 0 and 13 + 6 weeks. Results: Two hundred and thirty-nine women were included in the study. The mean gestational age at ultrasound examination was 12 weeks ± 5 days (±5.4 SD). All the 17 structures were seen in 155/239 fetuses (64.85%) at 2D evaluation and in 84/239 (35.15%) at 3D evaluation (p = 0.001). Comparing 2D and 3D visualization, the following anatomical structures showed a statistical difference: posterior fossa (92% vs. 74%, p < 0.005); neck (94.2% vs. 87.2%, p < 0.001); orbits (93% vs. 85.6%, p < 0.001); nasal bone (93% vs. 88.8%, p = 0.016); lung fields (99.5% vs 96.7%, p = 0.046); cardiac axis (99.5% vs. 83.9%; p < 0.001); bladder (97.5% vs. 91.7%, p < 0.001); abdominal wall (98.7% vs. 94.2%, p < 0.001). For the other anatomical portion, no statistically significant differences were found. Conclusions: Our study demonstrates that a full assessment of fetal anatomy is best performed using 2D ultrasound, while 3D ultrasound showed lower overall visualization rates, with comparable performance for selected structures, suggesting a potential supplementary use in specific clinical contexts.