Assessment of nuchal translucency thickness and the fetal anatomy in the first trimester of pregnancy by two- and three-dimensional ultrasonography: a pilot study.

Aim: To evaluate the use of three-dimensional ultrasonography (3D) as an alternative for examining fetal anatomy and nuchal translucency (NT) in the 1(st) trimester of pregnancy.

Method: Prospective study of 199 low risk pregnant women undergoing 1(st) trimester ultrasound scan for fetal anomalies. The NT and fetal anatomy were evaluated by three-dimensional (3D) ultrasonography after the standard two-dimensional (2D) examination. The gold standard in this study was the 2D ultrasonography.

Results: In some of the evaluated parameters the 3D method approaches the conventional 2D results. These parameters are the crown-rump length (CRL), the skull - brain anatomy (93.5%), the spine (85.4%), the upper (88.4%) and lower limbs (87.9%) and the examination of the fetal abdomen (98.5%). Some of the anatomic parameters under evaluation revealed a statistically significant difference in favor of the 2D examination. During the 3D examination the nasal bone was identified in 62.1% of the cases, the stomach in 85.9%, and the urinary bladder in 57.3% of the cases. The NT was assessed accurately in half of the cases compared to 2D examination.

Conclusion: The 3D ultrasound is insufficient for the detailed fetal anatomy examination during the 1(st) trimester of pregnancy. Nevertheless, the method might be improved in order to be considered as a screening method.