Abdominal Pregnancy

Abdominal pregnancy is implantation of the gestational sac in the peritoneal cavity, outside the uterus, tubes and ovaries.

It is usually secondary to tubal rupture or abortion with reimplantation.

It occurs in about 1 in 10,000 to 1 in 25,000 pregnancies and carries a much higher maternal mortality than tubal ectopic because of haemorrhage from placental attachment to bowel, liver or great vessels.

Risk factors: previous tubal disease, assisted reproduction, uterine scar defects.

May reach advanced gestation undetected.

Perinatal mortality is high.

• Patients may have persistent abdominal pain, nausea, fetal movements felt as painful, and easily palpable fetal parts. The cervix is displaced and the uterus is separate from the fetus.

• Abnormal fetal lie on palpation.

• Painful fetal movements.

• Failed induction of labour with oxytocin.

• Differential diagnosis: intrauterine pregnancy with abnormal lie, uterine rupture, placenta previa, fibroid, ovarian tumour.

• Complications: haemorrhage, infection, bowel obstruction, fetal death, lithopaedion, coagulopathy, maternal death.

The approach is ultrasound, with magnetic resonance imaging to define the placenta.

• Ultrasound: empty uterus, fetus outside the uterus, absent myometrium between fetus and bladder, no amniotic fluid.
• Magnetic resonance imaging to define placental attachment where available.
• Full blood count, clotting screen, blood group and Rhesus status, cross-match 6 units.
• Serum alpha fetoprotein may be raised.

The principle is surgical delivery in a facility with blood, a surgeon experienced in laparotomy and intensive care.

• Supportive: admission; two large-bore cannulae; cross-match 6 units; correct anaemia and coagulopathy before surgery in stable patients; bowel preparation if time allows.
• Pharmacological: antibiotic prophylaxis with ceftriaxone 1 g IV single dose plus metronidazole 500 mg IV at induction; tranexamic acid 1 g IV over 10 minutes; analgesia with paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours) and morphine 2.5 to 5 mg IV as required; no methotrexate after the first trimester with placenta left in place, as it causes rapid necrosis and sepsis.
• Procedures: laparotomy with delivery of the fetus; if the placenta is attached to vital organs, ligate the cord close to the placenta and leave it in place; remove the placenta only if the vascular supply can be controlled; drain the abdomen; postoperative monitoring in a high dependency unit.
• Special groups: Rhesus negative women give anti-D immunoglobulin 250 IU IM within 72 hours.
• Red flags: sudden pain, collapse, bleeding, fever, ileus.
• Follow-up: daily review in hospital; ultrasound and hCG weekly if placenta is left in place; antibiotics and observation for infection; counsel on risk and early scan in future pregnancies.