Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine (Phe) metabolism characterized by deficient activity of the hepatic enzyme, phenylalanine hydroxylase. Increased blood Phe levels are toxic to a variety of tissues, particularly the developing fetal brain. The mainstay of treatment for PKU is the dietary restriction of Phe, which results in decreased blood Phe levels. Lifelong dietary restriction and therapy improves quality of life in patients with PKU and should be encouraged. Genetic counseling is recommended for all reproductive-aged women with PKU, and should include information on reproductive choices and family planning as well as management of maternal PKU. If possible, pregnant women with PKU or hyperphenylalaninemia should be monitored in consultation with practitioners from experienced PKU centers. Optimally, treatment of neonates diagnosed with PKU should be initiated within the first week of life. All unaffected children of women with PKU are carriers and should receive genetic counseling when they are able to understand the consequences. Consultation with a genetics professional to discuss reproductive options is recommended.