The reason that an omphalocele occurs and therefore the process that goes wrong, is ambiguous. [3] A key factor is a failure of the physiologically protruded midgut, in the sixth to 10th weeks, to return from the umbilicus after the first stage of rotation. [11] It is unclear what drives the intestinal loop back into the body cavity but an omphalocele results from an omission of this process. [9] Possibly causal to this, the abdominal cavity may not have expanded enough to fit in the intestines and therefore remain in the umbilical cord.
Associated with this herniation, an incomplete closure of the lateral folds during week 4 is suggested to contribute to an omphalocele transpiring. [11] Diagram 5 illustrates how if the folds did not fuse together, there would be a gap in the gut tube. This provokes a defect or opening in the abdominal wall resulting in the intestines and possibly other organs to leak outside of the embryo. [13]
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Omphalocele could also be due to the abdominal muscles not enclosing the enlarged opening produced by the herniation of the midgut. [3] A narrow opening may be left after the completed return of the intestinal loop by week 11, allowing the intestines to herniate again. [13] All of these abnormalities could cause an omphalocele and in any case it may be a combination of the above that results in the abdominal contents protruding in a membranous sac at birth.