Omphalocele is a defect in the abdomen caused by the absence of abdominal muscles, connective tissue, and skin which causes the abdominal organs to protrude outside of the body, covered only by a thin, transparent membrane. Omphaloceles can vary in size, location, and the organs that are contained within the defect. A distinct feature of omphaloceles is the abnormal insertion of the umbilical cord into the membrane.
The incidence rate for omphaloceles ranges from 1 in 4,000 to 1 in 7,000 live births. The incidence of abdominal wall defects is twenty times greater in stillbirths than live births, and when stillbirths are included, the incidence rate ranges from 1 in 300 to 1 in 4,000 pregnancies.
Omphalocele is a distinct diagnosis from gastroschisis, which is always located to the right of the belly button and has normal umbilical cord insertion. In an omphalocele, the protruding organs are covered by a membrane, but the organs are directly exposed to amniotic fluid in cases of gastroschisis. Omphaloceles are associated with chromosomal abnormalities which is not the case with gastroschisis.
Omphaloceles can occur as an isolated diagnosis or in conjunction with other anomalies. Additional abdominal abnormalities occur in 50-70% of cases of omphaloceles. Chromosomal abnormalities are present in 30 to 69% of cases, with trisomy 18 being the most common diagnosis. Omphaloceles are also associated with congenital heart defects like ectopia cordis, cephalic disorders like acrania and anencephaly, pentalogy of Cantrell, anomalies of the skeletal and central nervous systems, abnormal amniotic fluid such as oligohydramnios and polyhydramnios, and, in 50% of cases, pulmonary hypoplasia can cause complications.
Preterm labor occurs in 36% to 65% of cases of omphaloceles. Repeat ultrasounds are recommended during pregnancy as 6% to 35% of cases are complicated by intrauterine growth restriction (IUGR). Omphaloceles are associated with a high perinatal mortality rate when additional anomalies are present. The recurrence risk for omphaloceles varies depending on the underlying cause.