Ovarian pregnancy: report of four cases and review of the literature.

Ovarian ectopic pregnancy is rarely seen; it constitutes only 0.5-3% of all ectopic pregnancies and the incidence is only 1 for every 7000-40,000 deliveries. We herein report four cases of primary ovarian pregnancy encountered during the last 10 years in Miyazaki prefecture, Japan. The patients in all of these cases were admitted to their local hospitals with increased lower abdominal pain and intraperitoneal bleeding, and had surgery for total or partial oophorectomy. Grossly and microscopically, chorionic villi were exclusively found in the ovary but not in the fallopian tube, so that we diagnosed these cases as primary ovarian pregnancies. None of the patients were known to have used an intrauterine contraceptive device, which have been suggested as the cause of ovarian pregnancies in several studies. The incidence of ovarian pregnancy is recently increasing, and pathologists will have increased chances to diagnose this disease.