What are the developmental milestones for a 100-day-old infant?

The developmental milestones of a 100-day-old infant can reflect their growth status. The following are some common developmental standards: 1. Weight and length: At 100 days old, an infant's weight is approximately 2.5 to 3 times their birth weight, with an increase in length of about 15-20 centimeters. Their weight and length should fall within the normal range of the growth curve. 2. Motor skills: Infants at this age can lift their head and chest while lying on their stomach, and gradually begin to grasp toys with their hands. Most infants are able to bring toys to their mouth and begin showing interest in their surroundings. 3. Visual and auditory responses: A 100-day-old infant can track moving objects with their eyes, shows clear responses to sounds, and can recognize familiar voices and faces. Typically, infants can turn their head toward the source of a sound and demonstrate interest in brightly colored objects. If significant developmental delays or other abnormalities are observed in the infant, it is recommended to seek medical attention promptly.