Intrauterine synechiae is the presence of fibrous adhesions inside the uterine cavity. In over 90% of cases, uterine adhesions formation is caused by uterine curettage especially if performed during the postpartum period or surgical abortions. Uterine curettage performed during these periods can damage the lining of the endometrium, allowing myometrial areas to contact each other, forming intrauterine adhesions. Other less common causes include uterine surgery such as hysteroscopic myomectomy or metroplasty and infectious endometritis, that rarely produces adhesions except when caused by tuberculosis.
If a patient with uterine sinequia becomes pregnant, the intrauterine synechia gets rodeated by amnion, which is seen on ultrasound as a band inside the uterine cavity. These sonographic findings were originally described by Mahony who described 7 cases. They created the term “Amniotic sheet” to describe the image in a cross-sectional sinequia seen encompassed by the amnion. This image of an undulating band with an oval image at its free end, which is corresponding to the sinequia, has also been called “The sperm sign.”