Differential diagnosis of first trimester ventral wall defect.

Documentation of early fetal developmental events has become possible with the use of high-resolution sonography. We report two cases of first trimester physiologic bowel herniation and contrast them with a first trimester diagnosis of omphalocele. The normal development of the fetal abdominal wall and the mechanisms proposed for pathogenesis of omphalocele are reviewed. The sonographic differentiation between physiologic herniation and pathologic ventral wall defects may be very subtle, making definitive first trimester diagnosis difficult.