Child Development Guide: Ages and Stages

Milestones, ages and stages

Child Development

Understanding your child’s changing growth and development milestones is an important part of parenting. As infants and children progress through a series of growth stages, they may encounter common physical or emotional challenges. The pediatric experts at CHOC created a series of guides by age and stage, so you can better understand what your child is going through and spot any issues along the way. 

Understanding your child’s growth and development

Growth and development includes not only the physical changes that occur from infancy to adolescence, but also some of the changes in emotions, personality, behavior, thinking and speech that children develop as they begin to understand and interact with the world around them. Skills such as taking a first step or smiling for the first time are called developmental milestones.  

Development Skills and Milestones 

Children reach milestones in how they play, learn, speak, act and move. All children develop at their own pace, but these milestones give you a general idea of the changes to expect as your child grows.  

Developmental milestones can be categorized by the following: 

Measuring Physical Child Development: Growth Charts

Kids grow at their own pace. There are a wide range of healthy shapes and sizes among children. Genetics, gender, nutrition, physical activity, health problems, environment and hormones all play a role in a child’s height and weight, and many of these can vary widely from family to family. 

Doctors consider growth charts along with a child’s overall well-being, environment and genetic background. Your child’s doctor may also consider: 

  • Is the child meeting other developmental milestones? 
  • Are there any other signs that a child is not healthy? 
  • What height and weight are the child’s parents and siblings?  
  • Was the child born prematurely? 
  • Has the child started puberty earlier or later than average? 

Are All Kids Measured on One Growth Chart?

No. Girls and boys are measured on different growth charts because they grow in different patterns and at different rates. One set of charts is used for babies, from birth to 36 months. Another set is used for kids and teens ages 2–20 years old. Also, special growth charts can be used for children with certain conditions, such as Down syndrome, or who were born early. 

What Could Signal a Problem? 

Keeping an eye on growth charts may help you or your child’s doctor spot any potential growth issues. Some patterns to look out for include: 

  • When a child’s weight or height percentile changes from a pattern it’s been following. For example: If height and weight have both been on the 60th percentile line until a child is 5 years old, and then the height drops to the 30th percentile at age 6, that might suggest a growth problem because the child is not following his or her usual growth pattern. But changing percentiles doesn’t always mean there’s a problem. Many kids may show changes in growth percentiles at some points in development, when it’s normal for growth rates to vary more from child to child. This is particularly common during infancy and puberty. 
  • If a child’s height progression is very different from what is expected by his or her midparental height calculation. 
  • If there is an abnormally low or high body mass index (BMI <5% or >85%).  

Growth charts are a helpful tool, but it is important to know that they do not paint a full picture of your child’s development or overall health. If you have any questions or concerns about your child’s growth — or growth charts — talk with your pediatrician. 


Reviewed by Dr. Mary Choi, Seaview Pediatrics, CHOC Primary Care – June 2021

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