Developmental Milestones

Recently, the CDC in collaboration with the AAP (American Academy of Pediatrics) shared the new developmental milestones guidelines. This is based on the information provided by 13 developmental experts and pediatricians. The original guidelines were established in 2004 and had not changed since then. The CDC states "Developmental milestones are things most children can do by a certain age.". They are observed behaviors and not necessarily follow the neurological development. The original guidelines were based on 50% of the population versus the new guidelines which are based on 75% of the population.

Through the past decade, we have seen a significant growth in developmental delays. During 2014–2016, the prevalence of children aged 3–17 years who had ever been diagnosed with a developmental disability increased from 5.76% to 6.99%. The following graph from the CDC demonstrates these rates, please refer to the resources for the citation.

What are some of the changes:

  • Removal of crawling as a milestone. Crawling is an essential portion for the neurological development. Some of its benefits are coordination, primitive reflexes integration, muscle tone development, improve sensory integration, and helps to develop secondary curvatures of the spine.
  • Talking has been delayed 3-6 months. According to the new guidelines, a 4-year-old should be able to communicate sentences of 4 words or more.
  • Walking was changed from 12 months to 18 months.
  • Adding checklists for ages 15 and 30 months so there is now a checklist for all well-child visit from 2 months to 5 years.
  • New social and emotional milestones.

The concern with this changes are: why are the milestones being changed instead of analyzing what's causing all of these delays? This can lead to later detection of delays resulting in delayed treatment. Developmental milestones follow an order according to the neurology of a child. If a milestone is skipped, it may cause delays with the next milestone.

Research tells us that 90% of the motor and sensory integration is reached by 6 years of age. Between birth and 2-3 years of age, the number of synapses in the brain increases from 2,500-15,000 per neuron. This is the peak of neruoplasticity. This is followed by the fastest rate of pruning which occurs between 2-16 years of age. The earlier a delay is detected and properly treated, the easier it will be for the child to overcome those delays. Following the new guidelines, many of the milestones may go undetected for a longer period of time. Keep in mind that these guidelines are based solely on observation. They reflect what common is, not what the normal should be.

Going forward, it will continue to be our responsibility to educate our patients based on the best available research and clinical expertise.


Cafasso, J. (2018, September 18). Synaptic pruning: Definition, early childhood, and more. Healthline. Retrieved from

Dennis, M., Spiegler, B.J., Simic, N. et al. Functional Plasticity in Childhood Brain Disorders: When, What, How, and Whom to Assess. Neuropsychol Rev 24, 389–408 (2014).
Tremblay, S. (2019, March 2). Could adult brain cell growth change the way we think about aging? Sciencing. Retrieved from

Zablotsky B, Black LI, Blumberg SJ. Estimated prevalence of children with diagnosed developmental disabilities in the United States, 2014–2016. NCHS Data Brief, no 291. Hyattsville, MD: National Center for Health Statistics. 2017


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