Abstract:Purpose: To evaluate the use of three-dimensional off-line ultrasonography (3D) as an alternative for examining fetal anatomy and nuchal translucency (NT) in the 1st trimester of pregnancy. Method: A Prospective study of 1007 low risk singleton pregnancies at 11 to 14 weeks of gestation. The gestational age, NT and fetal anatomy (10 anatomic features) were evaluated by off-line three-dimensional (3D) ultrasonography after the standard two-dimensional (2D) examination. The results of the two methods were compared using the 2D as a gold standard. Results: In some of the evaluated parameters the 3D method approximates the conventional 2D results. These parameters are the crown-rump length (CRL), the skull - brain anatomy (96.8%), the spine (89.7%), the upper (91.1%) and lower limbs (87%) and the fetal abdomen (98.5%). Some of the anatomic features revealed statistically significant differences in favor of the 2D examination such as the nasal bone (70.6% with the 3D), the stomach (79.6%) and the urinary bladder (59.6%). The NT was measured with the 3D in 87.5% of cases; although in only 60% values were accurate to the corresponding 2D. Conclusion: The off-line assessment of 3D ultrasound volumes can accurately date gestation and satisfactorily visualize fetal anatomy in about 75% of cases. Yet it seems insufficient for the 1st trimester examination, although with modifications and improvements it might serve a potential screening tool especially for areas with difficult access to advanced prenatal diagnosis.