Phenylketonuria is usually screened during the neonatal period through routine blood testing, where the level of phenylalanine in the blood is measured to screen each newborn. This enables early diagnosis and treatment, hence reducing the occurrence of intellectual disabilities. Phenylketonuria can also be screened prenatally before the birth of the newborn. It is an autosomal recessive genetic disorder, closely related to chromosomal abnormalities. Therefore, prenatal screening can be conducted by amniocentesis between the 16th to 20th weeks of pregnancy. Chromosomal abnormalities detected through the amniocentesis indicate that the fetus carries the pathogenic gene, meaning the child will be born with phenylketonuria. If both parents carry related genes, it is crucial to undergo prenatal screening and chromosomal analysis to eliminate the risk of the fetus developing the condition.