The Moebius syndrome consists of congenital seventh nerve palsy associated with other cranial nerve palsies, most often of the sixth, and/or musculoskeletal abnormalities. A retrospective study of the events of pregnancy in 15 cases was undertaken, after a rat animal model showed that abdominal trauma, uterine vessel clamping and handling and hyperthermia caused bilateral brainstem lesions in fetal rats. Eight of the 15 cases surveyed included a possible associated event during pregnancy; hyperthermia, previous uterine surgery, electric shock, failed abortion, prolonged rupture of the membranes, or alcohol abuse. These events can be correlated with animal studies that involve acute uteroplacental vascular insufficiency produced by a variety of methods. The cause of most cases of Moebius syndrome is probably a transient ischemic/hypoxic insult to the fetus.