Definition and diagnosis of cesarean scar ectopic pregnancies.

Cesarean scar ectopic pregnancy is a rare type of ectopic pregnancy, where the pregnancy implants into a myometrial defect caused by a cesarean scar. Its incidence is predicted to increase, given the global increase in cesarean deliveries. As most cesarean scar ectopic pregnancies present as failing pregnancies or patients choose termination of pregnancy, there are limited data on their natural history. However, early first trimester diagnosis is essential, given the associated significant maternal morbidity. Transvaginal sonography is generally considered to be the optimal method for diagnosing cesarean scar ectopic pregnancy. There is no evidence that MRI adds to the diagnostic accuracy, and it is therefore not recommended for routine evaluation of cesarean scar ectopic pregnancy. There is no agreed reference standard for the diagnosis of cesarean scar ectopic pregnancy; therefore, the validity of several proposed sonographic diagnostic criteria reported by different authors remains unknown. There are also various suggested classification systems for cesarean scar ectopic pregnancy, which divide them in differet types. However, the proposals are very heterogeneous, and superiority of one classification system over another is yet to be established.