Definition: A variety of ectopic pregnancy defined as an intraperitoneal implantation exclusive of tubal, ovarian or intraligamentous implantation

Incidence: 1.09:10,000 births. 9.2 abdominal pregnancies per 1000 ectopic gestations in the USA.¹

Etiology: Abdominal pregnancies are thought to result from tubal abortion or rupture with subsequent reimplantation of the conceptus onto bowel, omentum or mesentery.

Case report:

A case of term abdominal pregnancy is reported. Thes images were obtained during a term ultrasound examination. Note the images below the fetal presentation. They can be misdiagnosed as a fibroid.

A C-section was performed obtaining a healthy newborn.

Diagnosis: An abdominal pregnancy may be difficult to differentiate from a normal intrauterine pregnancy.

An elevated maternal serum alpha-fetoprotein in the absence of any other abnormalities should raise a suspicion.²

Risk factors include:

• Infertility
• Previous pelvic infection
• Congenital anomalies
• Endometriosis
• Previous ectopic pregnancy

The clinical presentation depends on the gestational age:

• In the first trimester, symptoms are similar to those of a tubal ectopic pregnancy.
• In the second or third trimester, the diagnosis may be suspected because of an abnormal fetal presentation, displaced uterine cervix or easily palpable fetal parts.

An undiagnosed abdominal pregnancy, which progresses to term, may be asymptomatic. Indirect clues for this diagnosis are:

• The inability to stimulate uterine contractions with oxytocin.

• Abnormal fetal lie.

• Oligohydramnios or intraperitoneal  maternal fluid.

• Impossibility to delineate uterus.

To diagnose an abdominal pregnancy on ultrasound, one should try to delineate the uterus as a separate structure form the fetus and placenta. In some cases MRI can be useful to demonstrate the relationship between the fetus,the cervix and myometrium.³

Prognosis: Abdominal pregnancy is a serious and potentially life-threatening condition. The maternal mortality rate is estimated between 0.5 and 18%. The perinatal mortality rate ranges between 40-95%.⁴ The deleterious effect of abdominal pregnancy on the mother and fetus is partly related to the morbidity of the surgical interventions.

Management: The diagnosis is frequently not made until laparotomy. Regardless of gestational age, removal of the placenta can result in hemorrhage. Angiographic arterial embolization may be considered as an option for such cases.⁵ The placental blood supply can be ligated and the pelvic organs upon which implantation occurred removed. If the placenta is not manipulated, the umbilical cord can be ligated close to the placenta and left in situ. Placental involution can be followed by serial ultrasounds and serum b-hCG titers. Some have advocated the use of methotrexate with varying degrees of success. Risks associated with leaving the placenta in situ include bowel obstruction, fistula formation and sepsis as the tissue degenerates.

References:

1. Atrash HK, Friede A, Hogue CJR. Abdominal pregnancy in the United States: frequency and maternal mortality. Obstet Gynecol 1987; 69: 333.
2. Tromans PM, Coulson R, Lobb MO, Abdulla U. Abdominal pregnancy associated with extremely elevated serum alphafetoprotein: case report. Br J Obstet Gynaecol 1984; 91:296.
3. Harris MB, Angtuaco T, Franzer CN, Mattison DR. Diagnosis of a viable abdominal pregnancy by magnetic resonance imaging. Am J Obstet Gynecol 1988; 159: 150.
4. Martin JN, Sessums JK, Martin RW, Pryor JA, Morrisson JC. Abdominal pregnancy: current concepts of management. Obstet Gynecol 1988; 71: 549-57.
5. Kivikoski AI, Martin C, Weyman P et al. Angiographic arterial embolization to control hemorrhage in abdominal pregnancy: a case report. Obstet Gynecol 1988;