Diagnosing omphalocele

Omphaloceles can be diagnosed in the first trimester:

http://www.fetalultrasound.com/online/text/34-055.htm

This article gives some guidance on early diagnosis:

http://www.fetalsono.com/teachfiles/bowelher.lasso

It suggests, “an omphalocele should be considered when the following observations are made: 1) the soft-tissue mass is larger than 7mm prior to 10 weeks and larger than 10 mm between 10 and 12 weeks gestation and is homogeneous in texture (due to the liver) 2) the "mass" is round and is as large, if not larger, than the embryonic abdomen, 3) the mass persists beyond 12 weeks gestation, or 4) other malformations are identified.”

This one suggests that by the time a fetus is 44mm long, herniation should not be visible:

http://emedicine.medscape.com/article/404182-overview