Excessive intake of vitamin A during pregnancy in the rat results in a marked litter failure. However, when litters are carried to term a variety of gross congenital anomalies are produced which include: encephaly, eye malformations, cleft palate, shortening of the mandible and maxilla, spina bifida with meningocele and hydrocephalus. Of 148 offspring of vitamin A-fed maternal rats, 77 exhibited gross malformations (an anomaly rate of 52%). There were no congenital anomalies observed in 1201 control young.

The 7th to 10th day of gestation was found to be the period critically susceptible to the teratogenic effect of vitamin A excess. The stage specificity of various environmental agents and the possible mechanism of action of the teratogenic effect of maternal vitamin A excess are discussed.

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