People who are considering having children may want to undergo genetic testing to see if they are carriers of the gene that results in phenylketonuria (PKU). In addition, the March of Dimes recommends that all women who were treated for PKU as a child have their blood phenylalanine levels checked prior to becoming pregnant. This can help a physician determine whether or not these women need to go on a special low-phenylalanine diet prior to conception. This type of diet can lower the woman’s risk of miscarriage or brain damage, congenital heart disease or microcephaly in the fetus.

Women should control phenylalanine levels both before and during pregnancy. Even mild levels of PKU in pregnant women present potential danger to the fetus. For this reason, women who were not treated for PKU as children still should have their blood phenylalanine levels checked if they have a family history of PKU.

Most experts recommend that patients with PKU should remain on a special diet throughout their lifetime. Previously, it was believed that diets could be ended around age six, when brain growth was completed. However, more recent study has revealed that high blood levels of phenylalanine may lead to a decrease in a child’s IQ (intelligence quotient) or to other developmental and behavioral problems