Effects of maternal phenylketonuria on the rat fetus

Abstract In chronically phenylketonuric rats, delayed intrauterine development was observed in spite of prolongation of gestation by 1 to 3 days. Bilateral cataracts (7 of 24 fetuses) and fetal resorption also were observed. These findings are in keeping with the high incidence of abortion, malformation, and mental retardation among the nonphenylketonuric offspring of phenylketonuric mothers. The phenylalanine level of both human and animal fetuses has been shown to be 2 to 6 times greater than that of the phenylketonuric mother, apparently due to active transport of amino acids by the placenta. It is suggested that the elevated level of phenylalanine in intrauterine life is especially disastrous due to the lack of an adequate blood-brain barrier in the mebryo.