Heel blood collection after birth can be used to screen newborns for inherited metabolic diseases, such as phenylketonuria, congenital hypothyroidism, G-6-PD deficiency, and congenital adrenocortical hyperplasia. 1. Phenylketonuria: belongs to autosomal recessive inheritance, this disease can lead to mental retardation and motor disorders of the children, there is no special clinical manifestation in the newborn period, and some of them may have feeding difficulties and vomiting, and newborn screening is an effective method for early diagnosis. 2. Congenital hypothyroidism: Newborns with congenital hypothyroidism may be asymptomatic or have only suspicious symptoms, such as low body weight, slow heart rate, hyperactivity, prolonged physiologic jaundice, feeding difficulties, and persistent constipation. Neonatal symptoms are atypical and early diagnosis depends on screening. 3. G-6-PD deficiency: newborns clinically present with hemolytic anemia and hyperindirect bilirubinemia, and severe cases can lead to bilirubin encephalopathy. 4. Congenital adrenocortical hyperplasia: newborns often present with depression, anorexia, vomiting, hyponatremia, hyperkalemia, dehydration and metabolic acidosis in the first 1 to 4 weeks of life, and circulatory failure can occur if diagnosis and treatment are not timely. Early screening can enable 70% of children to be diagnosed early before clinical symptoms appear. Currently, China requires that all newborns be screened for inherited metabolic diseases after birth in order to achieve early diagnosis and early treatment.