Exencephaly in human fetuses.

In some anencephalic fetuses exposed neural tissue mass of varied size can be demonstrated. This is known as exencephaly. The authors diagnosed by ultrasound 10 typical exencephalic cases prenatally between 14 and 21 weeks of gestation. Nine singular pregnancies were terminated and in the twin pregnancy a selective feticide of the exencephalic co-twin was carried out. The pregnancy continued to term and a healthy newborn infant and a fetus papyraceus were born. The mummified co-twin was anencephalic and showed only the remnants of the exposed brain. Authors suggest that, as in experiments with animals, the exencephaly in humans, by the degeneration of the exposed neural tissue converts to anencephaly and in this process the macrophages in fetal circulation and in the amniotic fluid may play a significant role. The large number of these actively phagocytic macrophages can be demonstrated in the amniotic fluid samples from exencephalic fetuses.