Maternal hyperthermia as a cause of "idiopathic" mental retardation.

Maternal hyperthermia of even short duration induces dramatic teratogenic (monster producing) effects in all experimental animals studied. In humans, several studies have reported cases analogous to some laboratory results in animal experiments, e.g., mental retardation, brain and nerve abnormalities and facial deformity. Recent computer-aided 3D reconstructions of pyramidal cells from guinea-pig brains subjected embryonically to a 1 hr stress at 44 degrees C environmental temperature, show that structural changes are induced in dendritic arbors. The alterations are greatest for dendritic segments closest to the cell body and are consistent with several reports linking topological and metrical anomalies with disturbances of brain function. We suggest that many cases of "idiopathic" subnormality are due to maternal hyperthermia during early pregnancy.