Developmental standards for 100-day-old babies are judged in terms of height, weight, head circumference, gross and fine motor movements. 1. Height: The height of a 100-day-old baby is 57.5-66.6cm for boys and 56.3-65.1cm for girls. 2. Weight: Normal weight is calculated as birth weight + age in months x 0.7, with a normal fluctuation range of 10%. The normal weight of a 100-day-old baby is 5.49-8.40kg for boys and 4.90-7.74kg for girls. 3. Head circumference: 100 days old baby’s head circumference is usually around 37-42cm, fontanel is not closed, between 1.5-2cm. 4. Gross and fine motor movements: 100-day-old babies should be able to raise their heads, roll over, and turn their heads freely from side to side in response to people walking around or sounds. They can reach out to grab things, put their hands together, and laugh out loud. Each baby’s own situation is different and is not a fixed value. As long as it is within the normal range, there is no need to worry too much.