A transverse vaginal septum is a congenital anomaly that occurs when the lower parts of the Müllerian ducts fail to completely fuse to the urogenital sinus, leading to a thin or thick wall of tissue remaining in the vagina. There is often a small opening in the tissue that allows some menstrual flow (partial obstruction), although obstruction may be complete as well. It can occur at any level of the vagina, from near the introitus to near the cervix.

A transverse vaginal septum occurs in approximately 1:21 000 to 1:70 000 patients. Its etiology is unknown. Often these are first noticed in adolescence, in relation to the start or expected start of menses or the onset of sexual activity.

Patients may present with complaints of inability to insert a tampon, inability to have penetrative intercourse, pain with intercourse, bleeding with or after intercourse, cyclic or acute pelvic pain, and abnormal or lack of menses.