Extending the successful prevention of mental retardation through newborn screening

When women with phenylketonuria (PKU) -a metabolic disorder diagnosed in newborns- do not follow a special diet, their babies are at risk for mental retardation. The results of a small interview study conducted by the Centers for Disease Control (CDC) are released today in the February 15, 2002 edition of the Morbidity and Mortality Weekly Report (MMWR). The article, "Barriers to Successful Dietary Control Among Pregnant Women with Phenylketonuria," states that two thirds of the participants in the study were not properly managing their diets at the time they conceived.

The prevention of mental retardation associated with PKU has been successful with the aid of newborn screening. Unfortunately, preventing maternal PKU-associated mental retardation is more challenging. Although a special diet for those diagnosed with PKU is recommended for life, it is often discontinued during adolescence. When women with PKU become pregnant and do not follow their diets, their babies are very likely to be affected by mental retardation and other birth defects. These birth outcomes are not caused by PKU in the infant, but by the mother's condition. Most of the birth defects can be prevented in babies if mothers maintain PKU-specific diets before and during pregnancy,

Dr. José Cordero, Director, National Center on Birth Defects and Developmental Disabilities, said the CDC study indicates several barriers might complicate affected women's ability to follow the lifelong diet, including cost, adverse tastes, and poor adherence to medical recommendations. "To ensure that women with PKU have healthy babies, it is critical that women stay on their special diets and that we find effective ways to help them and their babies," Cordero said. "To successfully prevent maternal PKU-associated mental retardation, these barriers must be addressed."

PKU is an inherited metabolic disorder that interferes with the body's ability to break down certain types of high protein foods such as meat, poultry, fish, eggs, and dairy products. Specifically, the body cannot process phenylalanine, an amino acid contained in proteins. Several decades ago, researchers discovered that mental retardation in babies born with PKU could be prevented through a special diet. Newborn screening programs to identify PKU and subsequently implement dietary management for affected babies followed. As a result, more than 3,000 women of reproductive age with PKU living in the United States were identified as newborns, placed special diets, and spared the severe mental retardation associated with PKU. Preventing mental retardation by screening newborns for PKU is now considered one of the greatest public health successes of the 20th Century.

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