Maternal PKU: A need for early identification

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Maternal PKU: A need for early identification
Bobbye M. Rouse, M.D.
University of Texas Medical Branch Galveston




The following was prepared for the feature article in the Texas Family Health Newsletter "Texas Talk".

PKU (Phenylketonuria) is an inherited disorder occurring in 1 out of 20,000 individuals. Persons with PKU cannot process the amino acid phenylalanine (phe) properly. Phe builds up in the blood and causes mental retardation if left untreated. Children are usually identified by newborn- screening test shortly after birth and placed on a phe-restricted diet. In the past, the diet was discontinued around school age. Some of these children began to lose IQ points. Currently, PKU clinics recommend continuation of the diet for life. Persons with PKU who have discontinued diet are advised to resume treatment.

Before newborn screening for PKU, women with PKU rarely reproduced as they were confined to institutions. After screening and early treatment, women with PKU began having children of their own. The women who had discontinued diet tended to have children with major birth defects called the Maternal PKU Syndrome. The problems included microcephaly, congenital heart defects, low birth weight and mental retardation. The Maternal PKU Syndrome must be addressed or the gain of preventing damage to children with PKU will be lost in one generation.

There is a dramatic difference in the outcome of children born with PKU and those damaged by the Maternal PKU Syndrome. The child born with PKU can be protected by early treatment but the damage caused to the fetus by the mother's high blood phe levels is irreversible.

There are women with PKU who are not on diet and at high risk for delivering infants with the Maternal PKU Syndrome. The difficulty is identifying these women and referring them to a PKU clinic for counseling. Family Planning clinic personnel can play a key role in assisting with this task by asking all patients the questions listed below. If the woman answers yes to any one of the items, a blood specimen should be sent to the Texas Department of State Health Services for phe and tyrosine analysis. Mothers who kept their blood phe levels between 2-6 mg/dL before and throughout pregnancy had the best chance of having a healthy baby.  

  • Were you on a special diet as a child?
  • Have you been told you might have PKU?
  • Have you had a baby with one of the following:
    Small head size, low birth weight, heart defect, or mental retardation?

If the patient's blood phe is elevated, the Newborn Screening Program, Texas Department of State Health Services, will recommend appropriate referrals.

Last updated December 21, 2010