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An abdominal pregnancy is a form of an ectopic pregnancy where the pregnancy is implanted within the peritoneal cavity outside the fallopian tube or ovary and not located in the broad ligament. While rare, abdominal pregnancies have a higher mortality rate than ectopic pregnancies in general but, on occasion, can lead to a delivery of a viable infant.
Less than 1% of ectopic pregnancies in the United States are abdominal, or about 1 out of every 10,000 pregnancies. A report from Nigeria places the frequency in that country at 34 per 100,000 deliveries. Risk factors are similar to tubal pregnancy with sexually transmitted disease playing a major role. 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 delivery (US data).
Implantation sites 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 implanted directly in the abdominal cavity and its organs, save for the tubes and ovaries; such pregnancies are very rare, only 24 cases had 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. To diagnose the rare primary abdominal pregnancy, Studdiford's criteria need to be fulfilled: tubes and ovaries should be normal, there is no abnormal connection (fistula) between the uterus and the abdominal cavity, and the pregnancy is related solely to the peritoneal surface without signs that there was a tubal pregnancy first.
A patient with an abdominal pregnancy may just display the normal signs of pregnancy or have non-specific symptoms such as abdominal pain, vaginal bleeding, and/or gastrointestinal symptoms. Frequently the diagnosis of an abdominal pregnancy is missed. However, it is a dangerous condition as it can bleed intraperitoneally resulting in a medical emergency with hemorrhagic shock and can be fatal; other causes of maternal death in patients with an abdominal pregnancy include toxemia[disambiguation needed], anemia, pulmonary embolus, coagulopathy, and infection.
Suspicion of an abdominal pregnancy is raised when the baby‘s parts can be easily felt, or the lie is abnormal. Sonography is extremely helpful in the diagnosis as it can demonstrate that the pregnancy is outside an empty uterus, there is no amniotic fluid between the placenta and the fetus, no uterine wall surrounding the fetus, fetal parts are close to the abdominal wall, and the fetus is in abnormal lie. MRI has also been used with success to diagnose abdominal pregnancy. Elevated alpha-fetoprotein levels are another clue of the presence of an abdominal pregnancy.
Potential treatments consist of surgery with termination of the pregnancy (removal of the fetus) via laparoscopy or laparotomy, use of methotrexate, embolization, and combinations of these. Sapuri and Klufio indicate that conservative treatment is also possible if the following criteria are met: 1. there are no major congenital malformations; 2. the fetus is alive; 3. there is continuous hospitalization in a well-equipped and well-staffed maternity unit which has immediate blood transfusion facilities; 4. there is careful monitoring of maternal and fetal wellbeing; and 5. placental implantation is in the lower abdomen away from the liver and spleen. The choice is largely dictated by the clinical situation. Generally, treatment is indicated when the diagnosis is made; however, the situation of the advanced abdominal pregnancy is more complicated.
Advanced abdominal pregnancy
Advanced abdominal pregnancy refers to situations where the pregnancy continues past 20 weeks of gestation. In those situations, live births have been reported, so in a report from Nigeria with four live births out of a series of 20 abdominal pregnancies. Often, however, with advancement of the pregnancy the support for the fetus becomes compromised and the fetus dies. A patient may carry a dead fetus but will not go into labor. Over time, the fetus calcifies and becomes a lithopedion.
It is generally recommended to perform a laparotomy when the diagnosis of an abdominal pregnancy is made. However, if the pregnancy is past 24 weeks and the baby alive and medical support systems are in place, careful watching could be considered to bring the baby to viability (34–36 weeks). Women with an abdominal pregnancy will not go into labor. Delivery in a case of an advanced abdominal pregnancy will have to be via laparotomy. The survival of the baby is reduced and high perinatal mortality rates between 40-95% have been reported.
Babies of abdominal pregnancies often have birth defects due to compression in the absence of the amniotic fluid buffer. The rate of malformations and deformations is estimated to be about 21%; typical deformations are facial and cranial asymmetries and joint abnormalities and the most common malformations are limb defects and central nervous malformations.
Once the baby has been delivered placental management becomes an issue. In normal deliveries the contraction of uterus provides a powerful mechanism to control blood loss, however, in an abdominal pregnancy the placenta is located over tissue that cannot contract and attempts of its removal may lead to significant blood loss. Generally, unless the placenta can be easily tied off or removed, it may be preferable to leave it in place and allow for a natural regression. This process may take about four months and can be monitored by checking human chorionic gonadotropin levels. Use of methotrexate to accelerate placental regression is controversial as the large amount of necrotic tissue is a potential site for infection. Placental vessels have also been blocked by angiographic embolization.
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