Four cases of hyperphenylalaninaemia: studies during pregnancy and of the offspring produced.

Four cases of variant hyperphenylalaninaemia during pregnancy are presented. Babies born to mothers with blood phenylalanine concentrations of 4-8 mg/dl were normal and did not exhibit significant microcephaly, although one did have a major congenital anomaly (exstrophy of the bladder). The mother with blood phenylalanine concentrations of 6-12 mg/dl during pregnancy delivered three of four infants with mild microcephaly but normal intellectual function. The data suggest that phenylalanine concentrations of 4-8 mg/dl are reasonable and desirable during pregnancy in hyperphenylalaninaemic women. Furthermore, the data do not support or refute the justification hypothesis of Bessman et al.