An abdominal pregnancy is a rare type of ectopic pregnancy where the embryo or fetus is growing and developing outside the womb in the abdomen, but not in the Fallopian tube (usual location), ovary or broad ligament. Because tubal, ovarian and broad ligament pregnancies are as difficult to diagnose and treat as abdominal pregnancies, their exclusion from the most common definition of abdominal pregnancy has been debated. Others—in the minority—are of the view that abdominal pregnancy should be defined by a placenta implanted into the peritoneum. Signs and symptoms Symptoms may include abdominal pain or vaginal bleeding during pregnancy. As this is nonspecific in areas where ultrasound is not available the diagnosis was often only discovered during surgery to investigate the abnormal symptoms. They are typically diagnosed later in the developing world than the developed. In about half of cases from a center in the developing world the diagnosis was initially missed. It is a dangerous condition as there can be bleeding into the abdomen that results in low blood pressure and can be fatal. Other causes of death in women with an abdominal pregnancy include anemia, pulmonary embolus, coagulopathy, and infection. Risk factors Risk factors are similar to tubal pregnancy with sexually transmitted disease playing a major role; however about half of those with ectopic pregnancy have no known risk factors (which include damage to the Fallopian tubes from previous surgery or from previous ectopic pregnancy, and tobacco smoking). Mechanism Implantation sites can be anywhere in the abdomen but can include the peritoneum outside of the uterus, the rectouterine pouch (culdesac of Douglas), omentum, bowel and its mesentery, mesosalpinx, and the peritoneum of the pelvic wall and the abdominal wall. The growing placenta may be attached to several organs including tube and ovary. Rare other sites have been the liver and spleen, giving rise to a hepatic pregnancy or splenic pregnancy, respectively. Even an early diaphragmatic pregnancy has been described in a patient where an embryo began growing on the underside of the diaphragm. Primary versus secondary implantation A primary abdominal pregnancy refers to a pregnancy that first implanted directly in the peritoneum, save for the tubes and ovaries; such pregnancies are very rare, only 24 cases having been reported by 2007. Typically an abdominal pregnancy is a secondary implantation which means that it originated from a tubal (less common an ovarian) pregnancy and re-implanted. Other mechanisms for secondary