Tracking Milestones

Parents are often concerned about their child’s future development and what to expect. However, genetic providers and counselors may struggle to quantify the likelihood and range of developmental differences, as robust data specific to each genetic variation remains limited¹.

That’s why it is recommended to monitor each child’s growth individually, not so much to compare to other children, but to celebrate achievements and provide support during early formative years of growth.

Regular monitoring is recommended for all children ages 0–5 and can be especially important for those with genetic differences who may benefit from early support.

Growth curves and milestones charts can:

Equip genetic and primary care providers with visual tools to share information for new diagnoses.
Help monitor development and guide treatments for the growing population of prenatally diagnosed infants.
Allow parents to keep track of cut-off points in time when a therapy may be most beneficial.

Monitoring Development

Growth curves track a child's growth based on physical measurements like height, weight, and head circumference. They play a useful role in routine early age screenings to detect potential growth-related concerns, and allow for timely interventions when needed.

Growth curves are affected by external factors such as nutrition, healthcare, and family environment (see WHO Child Growth Standards), as well as DNA.

What are Growth Curves?

Skills such as smiling for the first time, waving “bye-bye” and taking a first step, are called developmental milestones. As they grow up, children reach milestones in how they play, learn, speak, act, and move. The milestone date is usually based on the age when 75% of children can do this activity.

Milestone charts are graphic representations of typical childhood development in the general population, at different ages. They help parents and professionals track progress and serve as a guide to know when to act early. Milestone trackers are apps that can help track your child’s progress using milestone checklists. Some provide checklists adjusted for babies born prematurely.

CDC’s free milestone tracker app

CDC's free digital online checklists

What are Milestone Charts?

Growth standards vary according to differences in DNA patterns. For instance, an extra X or Y often results in being taller than expected. It’s common for XXX, XXY (Klinefelter) and XYY (Double Y) adults to be 5 to 10 cm taller than the general population². However not all adults with an extra X or Y are taller than average, and children tend not to be noticeably taller than peers until puberty. Remember that every child develops at their own pace.

All development is good development. Regardless of developmental milestone “start points”, it’s a good sign when your child makes consistent steps forwards. Keep in mind that progress is rarely a gradual, smooth curve, and can happen in sudden “jumps and leaps”.

Delay does not equal deficit. Research shows that children with X and Y variations often develop intellectual abilities in line with their peers, especially with early support³⁻⁴. While some areas, like language or executive function, may need extra help, many children reach or exceed educational milestones. Early intervention, and parental support play key roles. Work to your child’s strengths, and don’t forget to celebrate achievements!

Things to Know

Researchers are working on developing milestone checklists adjusted for different genetic variations, including X & Y differences. Guidance has started emerging in scientific papers, see below:

Sample Guidance

2-48 months

1-7 years

Study in Progress

Age

eXtraordinary Babies Study Children’s Hospital Colorodo, USA

The TRIXY Early Childhood Study Leiden University, The Netherlands

Creating developmental growth curves and milestone charts for infants with sex chromososme trisomy (Tartaglia et al., 2023)

Neurocognitive and behavioral development in young children (1–7 years) with sex chromosome trisomy (Van Rijn et al., 2023)

What's Next?

Just as variations in development are normal in the general population, it is usual for children with genetic variations to follow somewhat different developmental paths than the average. If your child does not keep their own growth curve or is missing milestones, be sure to talk with your healthcare provider such as a pediatrician or development psychologist.

Consider sharing this resource with your child's healthcare professional or school if you feel it could be helpful.

Takeaway