Prevalence:

• Only bowel in the sac: 1 in 100 at 11 weeks’ gestation, 1 in 800 at 12 weeks, 1 in 2,000 at 13 weeks.
• Liver in the sac: 1 in 3,500 fetuses at 11 to 13 weeks.

Ultrasound diagnosis:

• Midline sac containing bowel and / or liver with umbilical cord at the apex.
• High exomphalos may contain the heart (pentalogy of Cantrell).
• Low exomphalos may be associated with cloacal abnormality and spina bifida (OEIS complex).
• Exomphalos containing bowel only at 11-13 weeks resolves by 20 weeks in 90% of cases.

Associated abnormalities:

• Chromosomal defects, mainly trisomies 18 or 13, are found in 30-50% of cases.
• Genetic syndromes, mainly Beckwith-Wiedemann syndrome, are found in 10% of cases.
• Defects in other systems, mainly cardiac, are found in 30-50% of cases.

Investigations:

• Detailed ultrasound examination, including echocardiography.
• Invasive testing for karyotyping and molecular testing for Beckwith-Wiedemann syndrome.

Follow up:

• Ultrasound scans every 4 weeks to monitor fetal growth and amniotic fluid. It is best to monitor growth through estimation of fetal weight by the Sieme formula which uses biparietal diameter, occipitofrontal diameter and femur length, rather than formulas using abdominal circumference.

Delivery:

• Place: hospital with neonatal intensive care and pediatric surgery.
• Time: 38 weeks. Earlier if there is evidence of poor growth or fetal hypoxia.
• Method: induction of labor aiming for vaginal delivery. Cesarean section reserved for obstetric indications, such as breech presentation and for giant exomphalos (sac containing >75% of liver) to avoid rupture and hemorrhage.

Prognosis:

• Isolated small / moderate exomphalos: survival >90%.
• Isolated giant exomphalos: survival 80%.
• Other defect: depends on defect, e.g. trisomy 18 is lethal.

Recurrence:

• Isolated: no increased risk.
• Part of trisomies: 1%.
• Part of Beckwith-Wiedemann syndrome: up to 50%.