Three-dimensional sonography in the differential diagnosis of interstitial, angular, and intrauterine pregnancies in a septate uterus.

Interstitial, angular, and cornual pregnancies and intrauterine pregnancies in an anomalous uterus are separate entities, and the impact of each condition on obstetric outcomes is completely different. However, there is considerable confusion in understanding and managing the natural course of each condition due to a lack of uniform terminology. The single most important factor for differentiating these types of pregnancies is to make an early diagnosis. The differences between interstitial, angular, and cornual pregnancies on 2-dimensional (2D) sonography are subtle. Although magnetic resonance imaging can be used to differentiate these conditions, it is not preferred as the initial assessment tool because of its limited availability and cost-effectiveness. Three-dimensional (3D) sonography has the advantage of providing views of the uterus that cannot be obtained with conventional 2D sonography. We describe 3 cases of interstitial, angular, and intrauterine pregnancies in a septate uterus that were clearly differentiated by 3D sonography. We demonstrate the differences in diagnostic imaging findings and emphasize the importance of 3D sonography in differentiating these entities.