Parents with phenylketonuria can undergo chromosome testing. Phenylketonuria is a common amino acid metabolic disease and an autosomal recessive genetic disorder. Currently, it is mainly screened after the birth of the child by testing the blood for phenylketonuria. Phenylketonuria can also be screened prenatally before the birth of the newborn. Screening can be conducted by extracting amniotic fluid from the pregnant woman for genetic screening through amniocentesis between the 16th and 20th weeks of pregnancy. If chromosomal abnormalities are detected through amniocentesis, it indicates that the fetus carries the pathogenic gene, proving that the child will have phenylketonuria after birth. Couples carrying related genes also need to undergo prenatal screening.