Maternal phenylketonuria: cause for concern among women with PKU.

The literature on maternal phenylketonuria (MPKU) is reviewed in terms of its identification, description, and treatment. A number of professionals have projected a rebound in the frequency of mental retardation associated with PKU since the discovery of MPKU. The lack of knowledge of the exact causal mechanism of the phenomenon and the absence of a consistently effective treatment are emphasized. Evidence gathered regarding the effectiveness of the low phenylalanine diet in the prevention of MPKU is presented, and the implications of this evidence are discussed. Issues surrounding both the phenomenon and possible preventive measures are also discussed. Finally, some questions and responsibilities to be considered by physicians, mental retardation professionals, and policy makers are presented.