Updated: May 13
Mommas are constantly told not to compare our babies to others. Indeed, every baby learns and grows at their own, unique pace. Yet it seems that the need to compare ourselves to our peers is an innate human trait, and there is comfort in knowing that our child is within the "normal" range for achieving major milestones.
Luckily for us, the World Health Organization (WHO) collected data to assess the attainment of six gross motor milestones by 816 children across the USA, Norway, India, Oman, and Ghana (WHO, 2006). The results provide age windows for when most healthy children achieve the milestone. The ranges provided represent the estimated 1st and 99th percentile, meaning all but 1% of children at each end of the age spectrum fell within the provided time frame.
Sitting without support: Average age 6.0 months, most children achieve this milestone between 3.8 and 9.2 months.
Standing with assistance: Average age 7.6 months, most children achieve this milestone between 4.8 and 11.4 months.
Hands-and-knees crawling: Average age 8.5 months, most children achieve this milestone between 5.2 and 13.5 months.
Walking with assistance: Average age 9.2 months, most children achieve this milestone between 5.9 and 13.7 months.
Standing alone: Average age 11.0 months, most children achieve this milestone between 6.9 and 16.9 months.
Walking alone: Average age 12.1 months, most children achieve this milestone between 8.2 and 17.6 months.
Below is a video example of milestone attainment with the age range highlighted:
These data reveal that normal, healthy children can achieve major milestones at very different ages. Whether baby starts walking after 8 months or they wait until a year and a half before forcing you to chase after them, they are working at their own pace and neither milestone age should cause concern. Enjoy each step of your little snowflake's development as it progresses!
WHO Multicentre Growth Reference Study Group. WHO Motor Development Study: windows of achievement for six gross motor development milestones. Acta Paediatr Suppl. 2006 Apr;450:86-95. doi: 10.1111/j.1651-2227.2006.tb02379.x. PMID: 16817682.