Exencephaly in fetal hamsters following exposure to hyperthermia

Exposure of pregnant hamsters on gestation day 8 to 40 or 41 degrees C for one hour caused an increased rate of resorption and a high frequency of exencephaly and encephalocele. Longer exposures often killed pregnant females. Hamsters that had fetuses with abnormalities usually experienced body temperature elevations of 3-4 degrees C above normal (37 degrees C).