Omphalocele (sometimes called "exomphalos") refers
to a condition in the fetus whereby some abdominal contents (small
and/or large intestine, stomach, and even liver) protrude through
a hole in the abdominal wall. Unlike in gastroschisis, the hole is in the middle of
the abdomen, right where the belly button would be. Instead,
there is a variable size defect (hole) covered by a membrane
(which somewhat protects the exteriorized organs). The umbilical
cord of the fetus inserts at the top of this membrane, rather
than on the abdomen itself. Although both omphalocele and gastroschisis
appear the same (intestines protruding outside the abdomen),
each condition has its own features. To learn more about gastroschisis,
here. Abdominal wall defects can be detected by ultrasound
from the third month of pregnancy on (14 to 15 weeks). As the
pregnancy progresses, diagnosis becomes more accurate: loops
of intestine can then be seen outside the abdomen, "floating"
into the amniotic cavity (arrow).
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Omphalocele occurs somewhat less often than gastroschisis, and is estimated to be present
in 1 of every 5,000 live births. It can be an isolated finding,
but omphalocele is also seen in a number of chromosomal anomalies
and other syndromes. The most common associated anomaly is a
heart defect; others include the Pentalogy of Cantrell (which includes heart,
and other defects) and cloacal exstrophy (a severe anomaly involving
the intestines, the bladder and pelvic organs). Omphaloceles
are also seen in trisomy 13 and trisomy 18, two severe chromosomal
anomalies. In all these cases, the omphalocele is only a small
component of the fetal condition, and the outcome will be largely
depend on the other anomalies, not on the omphalocele itself.
Because of the relatively common
association of omphalocele with other, vaster syndromes, many
have, in the past, painted a grim picture for all omphaloceles.
However, isolated omphaloceles have a prognosis similar to gastroschisis:
once the extruded organs can be replaced in the abdomen and the
defect closed, most of these children will have a normal life.
CAN BE DONE BEFORE BIRTH?
There is no reason to treat omphaloceles
before birth (i.e., try to operate on the fetus). However, some
measures can be taken once an omphalocele, or gastroschisis,
has been diagnosed by ultrasound. Additional diagnostic tests
may be necessary, particularly with omphalocele: an amniocentesis
may be indicated, with chromosomal analysis; and efforts should
be made to detect heart anomalies. The course of the pregnancy
can be altered in three ways:
1. Mode of delivery
If intestines and other organs are outside
the abdomen, it would seem logical that they would be at an increased
risk of being damaged during normal delivery. Some have therefore
advocated Cesarean section ("C-section") for all cases
of gastroschisis and omphalocele. In fact, the risk of injury
is only theoretical, and vaginal delivery does not put the baby
at an increased risk of complications. For that reason, most
(although not all) physicians now recommend normal delivery,
even for gastroschisis, unless there are obstetrical reasons
to proceed with a C-section. The main exception may be cases
of "giant" omphalocele," where a large portion
of the liver is exposed as well: here, there may be an increased
risk of liver trauma with vaginal delivery.
2. Place of delivery
As long as he or she
is inside the womb, the fetus with an omphalocele is relatively
well shielded from trauma and complications. After birth, however,
the exposed intestines and/or liver have to be protected from
direct trauma and infection. The baby can be safely transported
to a treatment center, as long as certain precautions are taken.
However, if the diagnosis of omphalocele has been made beforehand,
it would seem logical to have the baby be born directly in such
a treatment center (i.e., a center with a neonatal intensive
care unit and immediate access to a pediatric surgery service).
Therefore, we generally recommend that, if you are pregnant with
a fetus with gastroschisis or omphalocele, you plan to deliver
in such a tertiary institution. Your care will likely be transferred
to a Maternal-Fetal Medicine specialist at our institution, to
facilitate the transition to peri- and postnatal care.
3. Time of delivery
One of the concerns with gastroschisis is that the exposed bowel
becomes so damaged, that function is impaired and the baby may
end up staying in the intensive care for a long time. It is known
that many infants with gastroschisis have what appears to be
damaged bowel, with very thick, rigid loops of intestines containing
a "peel." One of the theories for this peel (and for
the fact that some babies have little or no peel at all) is that
prolonged exposure of the bowel to the amniotic fluid causes
progressive damage. In other words, limiting the amount of time
that the bowel is floating in this fluid (or even diluting that
fluid by infusing sterile saline water inside the womb) could
theoretically decrease the amount of peel and intestinal damage.
In omphaloceles, this is rarely a problem, because a membrane
envelops the organs and shields them from exposure. However,
that membrane can have ruptured (so-called ruptured omphalocele),
exposing the intestines to the same potential trauma as with