What are these normal ranges? For that, we can go to the data. The World Health Organization, using data from six countries, calculated the range of the 1st percentile to 99th percentile for each of a variety of outcomes among healthy children. The children they studied do not have diagnosed motor issues, so their argument is that this can be seen as the range of normal development.6 Milestone Range Sitting without support 3.8 months to 9.2 months Standing with assistance 4.8 months to 11.4 months Crawling (5% of kids never do) 5.2 months to 13.5 months Walking with help 5.9 months to 13.7
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