Congenital uterine abnormalities result from abnormal embryological development of the Müllerian ducts. The incidence of congenital uterine abnormalities is 5.5% in the general population and 13.3% among infertile women [1]. Correct diagnosis, appropriate classification and optimal treatment are important for these women. Among the numerous studies have been conducted to classify uterine abnormalities, the American Society for Reproductive Medicine (ASRM) classification remains widely accepted and popular [2], [3], [4], [5]. The European Society of Human Reproduction and Embryology (ESHRE) and the European Society of Gynecological Endoscopy (ESGE) published a new classification in 2013 that relies more on morphometric criteria [6]. In the most recent ESHRE-ESGE classification of uterine abnormalities, the others (class U1c) section was added under the definition of the dysmorphic uteri (class U1), and minor deformities that are distinct from the septate uterus are classified under this section [6]. However, this classification system does not explicitly discriminate the subtypes including the Y-shaped.

Recently, Pacheco et al. identified subtypes of the dysmorphic uteri and presented discriminative properties of Y-, I-, and T-shaped uteri [7]. However, their categorization was based on hysteroscopy findings rather than preoperative imaging and the authors described the Y-shaped uterus as narrowness of the cavity in the middle 1/3 due to concentric fibres, a small indentation of the fundus like the arcuate uterus, and angulated tubal ostia. Although these subtypes can be distinguished from each other subjectively, objective imaging criteria that will distinguish these three uterine anomalies from each other have not yet been determined. In addition, the clinical consequences of dysmorphic uteri subtypes have not yet been identified sufficiently [8,9]. However, in the absence of objective and standardized diagnostic criteria, clinicians cannot reproducibly investigate the clinical consequences of a specific condition.

The first step in clarifying the clinical significance of the Y-shaped uterus is the identification of a universally accepted diagnostic method with valid, reliable, and standardized criteria. Hence, we sought to establish reliable and reproducible diagnostic criteria for the Y-shaped uterus which can be utilized in routine clinical practice and for future investigations.