At 38 days of age, infants are better able to extend their limbs, distinguish the source of sound, and gaze at and track the movement of larger objects. For full-term infants, the signs of jumping and unsteady movements that are characteristic of newborns are gradually disappearing, and infants are able to extend their limbs and arms and legs better, although they are still curled up during sleep. At this time, infants can get used to the sounds around them and are able to recognize and locate the source of the sounds. Visual acuity is further developed, and infants are able to gaze at larger objects and track the unidirectional movement of a flashlight beam. Postnatal development is influenced by the circumstances of birth and feeding, and developmental status at 38 days varies among infants. If an infant’s development is not in line with the age of the month, it is necessary to consult a doctor in a timely manner to clarify the cause, and be guided by the doctor to regulate the treatment to avoid adverse consequences.