- increased levels of serum β-hCG and ultrasonography findings. The criteria for diagnosis by ultrasonography was the presence of the following: (1) an empty uterine cavity and endocervical canal; (2) detection of the placenta and/or a gestational sac embedded in the hysterectomy scar; (3) the presence of the gestation sac with or without a fetal pole and with or without fetal cardiac activity (depending on the gestational age) in the anterior part of the uterine isthmus; and (4) a thin (1-3 mm) or absent myometrial layer between the gestational sac and the bladder(24). All patients had taken Magnetic Resonance Imaging (MRI) to clarify the diagnosis . Pregnancy tissues were identified by histopathology examinations of the surgical tissues.