A type of ectopic pregnancy in which the embryo implants in the abdominal cavity instead of in the endometrium of the uterus. Less than 1% of ectopic pregnancies are implanted within the abdominal cavity. The pathogenesis of abdominal implantation is controversial. Many are the result of secondary nidation within the peritoneal cavity after tubal abortion. True primary abdominal implantation must satisfy the criteria of Studdiford : - normal fallopian tubes with no evidence of recent or remote trauma - absence of any uteroperitoneal fistula - presence of a pregnancy related exclusively to the peritoneal surface and early enough to eliminate the possibility of secondary implantation after a primary nidation within the tube. The most common abdominal implantation site is the posterior cul-de-sac, followed by the mesosalpinx, the omentum, the bowel and its mesentery, and the peritoneum of the pelvic and abdominal walls, including the anterior cul-de-sac. However, pregnancy implantation can occur anywhere in the abdomen, even elsewhere in the body, including the retroperitoneal space, the liver, the spleen, the appendix,...