The majority of fetuses with omphalocele have other congenital abnormalities and, in many cases, an abnormal karyotype. We retrospectively studied 22 consecutive fetuses with sonographically diagnosed omphalocele and available karyotype to determine whether the contents of the omphalocele could predict the karyotype. Of these 22 fetuses, 18 had normal and four had abnormal karyotypes. Sixteen of the karyotypically normal fetuses had liver herniated into the omphalocele and two had only bowel present in the defect. All four of the fetuses with abnormal chromosomes had only bowel in the defect.