Early in development, a portion of small bowel protrudes through the umbilicus alongside the two umbilical arteries that carry blood from the embryo to the placenta and the umbilical vein which is the single conduit for all of the blood flow from the placenta. Bowel is usually completely intrabdominal by 8 weeks after conception.   When the origin of the cord is bulged by intrab-abdominal contents, like bowel loops or even a portion of the liver,it is referred to as an umbilical hernia or omphalocele. About a third of cases with an umbilical hernia persisting after 10 weeks GA will have a chromosome problem.

Umbilical hernia and nuchal translucency are easy to see early in pregnancy and account for the majority of simple ultrasound screening indications for an amnio. Nuchal translucency is a sign that occurs between about 9 and 14 weeks gestational age (remember, gestational age = conceptual age plus two weeks). Umbilical hernias may persist throughout pregnancy, requiring repair after delivery, or they may regress between 12 and 16 weeks GA. One of the cardinal features of trisomy 21 (Down's Syndrome) is that developmental events occur, but along a time scale that is delayed relative to the norm. The delay may be different for each organ system. When coordination between systems is thrown off, function suffers and development may never become normal. When we evaluate embryoes and fetuses,we need to be aware of temporal factors as well as anatomic and physiologic issues.