Should my child have a WHO-GMM assessment?

Curious whether your little one's rolling, sitting and walking are on track? Here's what the WHO gross-motor windows really tell you.

In short

The WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM) is a reference framework — not a stand-alone test — that describes the broad age ranges in which healthy children typically reach six motor milestones: sitting without support, hands-and-knees crawling, standing with assistance, walking with assistance, standing alone, and walking alone. Most children do not need a separate "WHO-GMM assessment"; rather, a clinician uses these windows as one lens within a fuller developmental check. It is worth a look if your child seems clearly behind on gross-motor steps, but the windows are deliberately wide because healthy babies vary a great deal.

What the windows actually involve

The WHO milestones come from a large multi-country study of healthy children, so each milestone is given as a window (for example, walking alone anywhere from roughly the end of the first year into the second), not a single deadline:

• Six gross-motor milestones — observed through everyday movement, not a pass/fail exam.
• Wide, overlapping ranges — designed to reflect normal variation across babies and cultures.
• Observation, not equipment — a clinician watches how your child moves, holds posture, bears weight and transitions between positions.
• One piece of the picture — gross motor is read alongside fine motor, communication, social and play development.

So the honest answer to "should my child have one?" is: the windows are most useful when there is a specific concern — your child is well past a window, has lost a skill, or moves very differently on one side. In those cases the windows become a helpful prompt to seek a proper review.

When to seek a check

Book a developmental review if your child is clearly past a window (for example, not sitting with support well beyond the typical range, or not walking by around 18 months), has stiff or floppy muscle tone, strongly favours one side, or has lost a skill they once had. Persistent, marked delay deserves prompt attention — early movement support is gentle and effective.

The Pinnacle way

Developmental measurement supports care planning; diagnosis requires an appropriately qualified healthcare professional., under the care of a qualified clinician — never from an online chart or a single milestone window. Our clinicians use a structured, clinician-administered assessment that places gross-motor progress within your child's whole developmental picture, measured against their own baseline so real gains become a clear line. Backed by 2.5 billion+ data points and 25 million+ therapy sessions across 70+ centres, we turn each review into practical occupational and physical movement support you can use at home. You can read how the measure works here: what the AbilityScore is and how it's calculated.

Trusted sources

WHO Motor Development Study and Windows of Achievement for six gross-motor milestones; WHO and Nurturing Care guidance on early childhood development; CDC and HealthyChildren (AAP) developmental milestone resources for movement.

Next step — Not sure if your child's movement is on track? Book a developmental assessment with a Pinnacle clinician for clear, reassuring answers and a plan if needed.

This is general information, not a diagnosis — individual assessment and diagnosis require an appropriately qualified healthcare professional.