Diagnostic clues to ectopic pregnancy.

Ectopic pregnancy accounts for approximately 2% of all pregnancies and is the most common cause of pregnancy-related mortality in the first trimester. Initial evaluation consists of hormonal assays and pelvic ultrasonography (US). A history of pelvic pain along with an abnormal beta human chorionic gonadotropin level should trigger an evaluation for an ectopic pregnancy. The fallopian tube is the most common location for an ectopic pregnancy. An adnexal mass that is separate from the ovary and the tubal ring sign are the most common findings of a tubal pregnancy. Other types of ectopic pregnancy include interstitial, cornual, ovarian, cervical, scar, intraabdominal, and heterotopic pregnancy. Interstitial pregnancy occurs when the gestational sac implants in the myometrial segment of the fallopian tube. Cornual pregnancy refers to the implantation of a blastocyst within the cornua of a bicornuate or septate uterus. An ovarian pregnancy occurs when an ovum is fertilized and is retained within the ovary. Cervical pregnancy results from an implantation within the endocervical canal. In a scar pregnancy, implantation takes place within the scar of a prior cesarean section. In an intraabdominal pregnancy, implantation occurs within the intraperitoneal cavity. Heterotopic pregnancy occurs when an intrauterine and an extrauterine pregnancy occur simultaneously. A spectrum of intra- and extrauterine findings may be seen on US images. Although many of the US findings are nonspecific by themselves, when several of them are seen, the specificity of US in depicting an ectopic pregnancy substantially improves. (c) RSNA, 2008.