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 abdominal pregnancy include uterine rupture, rupture of a uterine rudimentary horn and fimbrial abortion. Diagnosis
Suspicion of an abdominal pregnancy is raised when the fetal anatomy can be easily felt, or the lie is abnormal, the cervix is displaced, or there is failed induction of labor. X-rays can be used to aid diagnosis.
Complications of leaving the placenta can include residual bleeding, infection, bowel obstruction, pre-eclampsia (which may all necessitate further surgery) and failure to breast feed due to placental hormones.Outcome with abdominal pregnancy can be good for the baby and mother, Lampe described an abdominal pregnancy baby and her mother who were well more than 22 years after surgery. Epidemiology
About 1.4% of ectopic pregnancies are abdominal, or about 1 out of every 8,000 pregnancies. A report from Nigeria places the frequency in that country at 34 per 100,000 deliveries and a report from Zimbabwe, 11 per 100,000 deliveries. The maternal mortality rate is estimated to be about 5 per 1,000 cases, about seven times the rate for ectopics in general, and about 90 times the rate for a "normal" delivery (1987 US data). History
Al-Zahrawi (936–1013) is credited with first recognizing abdominal pregnancy which was apparently unknown to Greek and Roman physicians and was not mentioned in the writings of Hippocrates; Jacopo Berengario da Carpi (1460–1530) the Italian physician is credited with the first detailed anatomical description of abdominal pregnancy. Natural experiment
Because pregnancy is outside the uterus, abdominal pregnancy serves as a model of human male pregnancy or for females who lack a uterus, although such pregnancy would be dangerous. Abdominal pregnancy has served to further clarify the disease pre-eclampsia which was previously thought (1980s) to require a uterus for it to occur, however pre-eclampsias occurrence in abdominal pregnancy (with the conceptus outside the uterus) helped throw light on pre-eclampsias etiology.