Maternal phenylketonuria is likely to have damaging effects on the offspring. Intrauterine growth retardation, postnatal growth retardation, microcephaly, mental retardation, congenital malformations in the infant, and spontaneous abortions in the mother suggest the possibility of maternal phenylketonuria even if the mother is of normal intelligence.
Fisch RO, Doeden D, Lansky LL, Anderson JA. Maternal PhenylketonuriaDetrimental Effects on Embryogenesis and Fetal Development. Am J Dis Child. 1969;118(6):847-858. doi:10.1001/archpedi.1969.02100040849007