Concordance for Cloacal Dysgenesis

Monozygotic (MZ) twins concordant for cloacal dysgenesis were diagnosed at 15 weeks’ gestation on ultrasound exam. The structural alterations result from abnormal morphogenesis of the cloacal membrane and contiguous anlage with resultant secondary changes. These defects are suggestive of teratogen exposure or an endogenous event early in gestation, resulting in MZ twinning and the development of a poly topic field defect.