Infancy generally refers to the period after birth when the baby reaches one year of age, it is the first peak of human growth and development, and another peak is puberty. The first three months after birth is the period of infant growth surge, in this stage the infant growth rate is quite fast, basically every day you can see the infant weight growth. In general, the weight and length growth of an infant in the first three months after birth is the sum of the growth in the last nine months. An infant’s length increases by about 12.5 centimeters in the first three months, and the weight is usually twice the weight at birth. Therefore, it is important to ensure that infants have adequate nutrition and sufficient sleep time during this period to ensure healthy physical growth.