Ectopic pregnancy is estimated to occur in 1 to 2 percent of pregnancies [1,2]. Over 90 percent are located in the fallopian tube, while the remainder implant in locations such as the abdomen, cesarean (hysterotomy) scar, cervix, and ovary . Given the rarity of implantation at these sites, much of the information surrounding diagnosis and treatment of these pregnancies has been derived from small observational studies and case reports. This makes the optimal approach to their evaluation and management difficult to determine.
Abdominal pregnancy, cesarean scar pregnancy, and heterotopic pregnancy will be reviewed here. The goal is to prompt clinicians to think of these diagnoses and to make suggestions for management, especially for avoiding catastrophe.
The diagnosis and management of ectopic pregnancies at other locations are discussed separately. (See "Clinical manifestations and diagnosis of ectopic pregnancy" and "Incidence, risk factors, and pathology of ectopic pregnancy" and "Methotrexate treatment of tubal and interstitial ectopic pregnancy" and "Surgical treatment of ectopic pregnancy and prognosis for subsequent fertility" and "Cervical pregnancy" and "Expectant management of ectopic pregnancy".)
Abdominal pregnancy refers to a pregnancy that has implanted in the peritoneal cavity, external to the uterine cavity and fallopian tubes. The estimated incidence is 1 per 10,000 births  and 1.4 percent of ectopic pregnancies [4-6]. There are reports of abdominal pregnancy occurring after hysterectomy [7,8].
Potential sites include the omentum, pelvic sidewall, broad ligament, posterior cul-de-sac, abdominal organs (eg, spleen, bowel, liver), large pelvic vessels, diaphragm, and the uterine serosa [5,9-17].