A teratogenic disorder observed in a newborn or child of a mother who was exposed to phenytoin during pregnancy. manifestations include dysmorphic craniofacial features, hypoplastic distal phalanges and nails, growth delay and delayed psychomotor development.

Fetal hydantoin syndrome, also called fetal dilantin syndrome, is a group of defects caused to the developing fetus by exposure to teratogenic effects of phenytoin. Dilantin is the brand name of the drug phenytoin sodium in the United States, commonly used in the treatment of epilepsy. It may also be called congenital hydantoin syndrome, fetal hydantoin syndrome, dilantin embryopathy, or phenytoin embryopathy. Association with EPHX1 has been suggested..