Anencephaly is the most common type of neural tube defect seen during prenatal development. This condition results from a failure of the neural tube to close at its cephalad end between the second and third weeks of embryonic development.1 Sonographically, anencephaly presents as the absence of the cranial vault and cerebral hemispheres. It is believed to be multifactorial in origin but usually not associated with chromosomal abnormalities.2 The condition is invariably lethal; 50% are stillborn, and the remainder die in the newborn period.3
We present a case of a twin gestation, with one fetus affected with anencephaly and the other with no apparent abnormalities.
