Vasa previa: prenatal detection by three-dimensional ultrasonography

Objective To describe three-dimensional (3D) ultrasonography (US) for the a ntepartum diagnosis of vasa previa. Design This was a descriptive study of two pregnant women who were suspecte d to have vasa previa by conventional gray-scale ultrasonography. Three-dim ensional studies were also performed during the early third trimester to fu rther investigate the possibility of this condition. Results In the first case, 3D US provided gray-scale multiplanar and surfac e-rendered views of an aberrant vessel over the internal cervical os. For t he second case, a 'flight-path' technique allowed the examiner to follow ax ial views of the endocervical canal toward the internal os until an aberran t vessel was verified. The 'niche-mode' analysis, with and without color po wer Doppler ultrasonography, was also used to confirm the diagnosis. Conclusion Three-dimensional ultrasonography offers several additional imag ing tools that are not currently provided by more conventional ultrasonogra phy for the detection of vasa previa. It represents an important adjunct to two-dimensional (2D) studies, especially when this diagnosis is questionab le.