When mothers with PKU have high blood phenylalanine levels during pregnancy, fetal birth defects or miscarriage can occur. Untreated PKU can lead to: Irreversible brain damage and marked intellectual disability beginning within the first few months of life. Neurological problems such as seizures and tremors.Click to see full answer. Accordingly, does PKU affect lifespan?PKU does not shorten life expectancy, with or without treatment. Newborn screening for PKU is required in all 50 states. If treatment begins no later than 2 to 3 weeks of a baby’s life, and the diet is strictly followed, the child with PKU can be normal.Also Know, what happens if you have PKU? Phenylketonuria (PKU) is a rare genetic condition that causes an amino acid called phenylalanine to build up in the body. Amino acids are the building blocks of protein. When this enzyme is missing, your body can’t break down phenylalanine. This causes a buildup of phenylalanine in your body. Also Know, is PKU dangerous? A: PKU is very serious if treatment is not started for within the first 2 to 3 weeks of life. Although symptoms may not be visible, exposure to high levels of phenylalanine after 2 to 3 weeks can have long lasting negative effects such as intellectual challenges. Untreated PKU can lead to intellectual disabilities.Is PKU testing required by law?A PKU screening test is a blood test given to newborns 24–72 hours after birth. Although PKU is rare, all newborns in the United States are required to get a PKU test. The test is easy, with virtually no health risk. But it can save a baby from lifelong brain damage and/or other serious health problems.