Three-Dimensional Ultrasound for Nuchal Translucency Thickness Measurements: Comparison of Transabdominal and Transvaginal Ultrasound

Objective: We compared nuchal translucency (NT) thickness measurements using two-dimensional (2D) transabdominal, three-dimensional (3D) transabdominl, and 3D transvaginal ultrasound to determine levels of agreement.

Methods: One hundred one pregnant women with a median gestational age of 12.6 weeks (range 11-14 weeks) were inclucdced in this study. First-trimester NT thickness measurements with 2D transbdominal ultrasound were performed on all women and were used as the gold standard. They also underwent 3D transabdominal and 3D transvaginal NT examinations. Both methods were compared with 2D transabdominal ultrasound measurements with respect to fetal nuchal translucency thickness, and levels of agreement were calculated by correlation coefficient.

Results: There were no significantly different results between 2D transbdominal and 3D ultrasound. Furthermore, 3D transbdominl and 3D transvginl measurements did not differ significntly. When 3-mn NT thickness was used as a cut-off level, however, there was a statistically significant overrestimation of NT measurements by 3D transbdominal and 3D transvaginal ultrasound (median 1.4 mn versus 1.6 mm and 1.6 mm; P = .016 and P = .015 respectively) in the patient group with 2D transbdominal NT thickness less than 3 mm. In the patient group with 2D transbdominal NT thickness of 3 mm or more, there was a statistically significant understimation of NT measurements by 3D transabdominal ultrasound (median 5.0 mm versus 4.6 mm; P = .002).

Conclusion: Two-dimensional transabdominal and 3D transabdominal and 3D transvaginal NT measurements differed minimally but significantly when compared with each other.