Effects of Untreated Maternal Phenylketonuria and Hyperphenylalaninemia on the Fetus

Abstract
We studied the effects of maternal phenylketonuria and hyperphenylalaninemia on 53 offspring from untreated pregnancies in 22 mothers who were identified by routine screening of umbilical-cord blood. The IQ of the offspring was significantly correlated with both maternal IQ (r = 0.83, P<0.001) and maternal blood phenylalanine level (r = -0.82, P1100 μmol per liter) in the mother has a substantial cognitive effect on her offspring but that the effect of mild hyperphenylalaninemia may have been overstated in the past. (N Engl J Med 1983; 309: 1269–74.)