Phenylketonuria in Pregnant Women

Author: Monica Preboth
Date: August 15, 2000

The Committee on Genetics of the American College of Obstetricians and Gynecologists (ACOG) has issued a committee opinion on maternal phenylketonuria. ACOG Committee Opinion No. 230 appears in the January 2000 issue of Obstetrics and Gynecology.

According to the ACOG committee, phenylketonuria is an autosomal recessive disorder of phenylalanine metabolism. If left untreated, the condition can cause severe mental retardation. The committee reports that routine screening for phenylketonuria in newborns and early dietary therapy with a phenylalanine-restricted diet have reduced mental retardation in affected persons. Because of these advances in detection and treatment of the disorder, large numbers of young adults with phenylketonuria who received early dietary treatment have IQs in the normal or near-normal range.

However, a new public health challenge has emerged from young women with phenylketonuria who fail to adhere to dietary restrictions. Metabolically normal fetuses of women with phenylketonuria who are on an unrestricted diet may develop mental retardation (92 percent risk), microcephaly (73 percent risk), heart defects (12 percent risk) and low birth weight caused by maternal hyperphenylalaninemia.

The ACOG committee states, "It has been suggested that dietary control should be implemented at least three months prior to conception to help prevent fetal structural defects, including cardiac defects." If phenylalanine levels are normalized by eight weeks of gestation, evidence suggests that a reduction in intrauterine growth restriction will result.

The ACOG committee makes the following recommendations regarding women with phenylketonuria:

* All women with phenylketonuria should be strongly encouraged to receive family planning and preconception counseling.

* Women with phenylketonuria should restrict dietary phenylalanine before conception.

* Ideally, pregnant women with phenylketonuria should be managed in consultation with physicians from experienced phenylketonuria centers.

COPYRIGHT 2000 American Academy of Family PhysiciansCOPYRIGHT 2000 Gale Group

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