Background: Phenylketonuria is a rare inborn inherited disorder of metabolism disease 
due to an autosomal recessive trait. The prevalence in Egypt is one case per 7,500. When 
PKU untreated or delayed treatment, can lead to severe mental retardation, seizures and 
tremors, impaired growth and development. The present study was aimed to evaluate the 
effect of implementing nutritional intervention program for mothers on health parameters of 
their infants with phenylketonuria. Research design: A quasi-experimental research design 
was used. Setting: The study was conducted at pediatric outpatient clinic inherited and 
metabolic diseases of Tanta University Hospital. Subjects: A convenience sampling of 50 
mothers having infants with PKU who attended the previously mentioned setting. Two tools
were used to collect the required data: Constructed interview questionnaire sheet: to 
assess mothers' knowledge towards their infants suffering from Phenylketonuria. It 
consisted of three parts: Socio-demographic characteristics of mothers, infants, and 
mothers' knowledge regarding phenylketonuria, mothers' practices sheet: to assess 
mothers' practices regarding to infants' feeding. Observational chick list to assess 
outcomes of infants. Result: revealed that there were highly statistically significant 
differences between the pre-test and post-test of nutritional intervention program 
implementation for infants with Phenylketonuria. Conclusion: the present study was 
revealed that a significant improvement of mothers' knowledge and practice regarding 
phenylketonuria immediate and after one-month of program implementation, nutritional 
intervention program was effective on their infants' development and health parameters as 
increase weight . Recommendations: In-service training program should be conducted 
periodically and regularly in health care services for mothers with infants had 
phenylketonuria.