Rett Syndrome
When to worry about Rett Syndrome at 12–18 months
Rett Syndrome is rare and almost always affects girls, with typical early development followed by a slowing or loss of skills, usually between 6 and 18 months. In the 12–18 month window the signal to act on is regression — losing hand skills or words she once had, repetitive hand movements, slowing head growth or new unsteadiness — not a single delayed milestone. Because it has a genetic basis, any suspected loss of skills warrants a prompt paediatric and developmental review. A diagnosis is formed only at a Pinnacle centre under clinician care, never from a checklist.
If your little girl seemed to be growing beautifully and you've now noticed something has shifted, your watchfulness is loving and wise — let's make sense of it together.
In short
Rett Syndrome (ICD-11 LD90.0) is a rare genetic condition that almost always affects girls. Classically, development looks typical for the first 6–18 months, and then a child may slow down, plateau, or lose skills she had already gained — particularly purposeful use of the hands and emerging words. So in the 12–18 month window, the signal to act on is not a single milestone delay but a clear regression — a loss of skills she once had. This is a concern to have gently checked, never a diagnosis you should reach at home.What would genuinely warrant a check
In this age band, the patterns clinicians take seriously are changes from your child's own earlier ability:- Loss of purposeful hand use — she used to reach, grasp or point, and now seems unable to
- Repetitive hand movements — wringing, washing, tapping, squeezing or hand-to-mouth movements that replace useful hand skills
- Loss of babble or early words she had previously used
- Slowing head growth — your doctor may notice this on the growth chart
- New unsteadiness in sitting or walking, or walking that doesn't emerge as expected
- Reduced eye contact or social engagement after a period of being connected
A single late milestone, in isolation, is usually not this. It is the picture of regression — going backwards on skills already mastered — that should prompt a prompt medical and developmental review.
When and where to seek help
Because Rett Syndrome has a genetic basis (often involving the MECP2 gene) and can be confirmed with medical testing, any suspected loss of skills deserves a prompt paediatric and developmental review, not a wait-and-see approach. Early review also rules in or out the many gentler explanations for a temporary plateau — illness, a growth spurt, or simply a child's own pace. Your paediatrician can arrange the right medical assessment alongside a developmental check.The Pinnacle way
A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre, under qualified clinician care — never from an online form or a checklist. Our clinicians map your daughter's whole developmental story, coordinate with medical testing where needed, and build supportive, strengths-based occupational therapy and communication plans that protect her hand function, mobility and connection. Across 70+ centres and 25 million+ therapy sessions, families find a calm, expert team beside them from the very first question.Trusted sources
WHO ICD-11 (LD90.0, Rett Syndrome); American Academy of Pediatrics developmental surveillance guidance (healthychildren.org); WHO Nurturing Care Framework on early development.Next step — If you've noticed your daughter losing skills she once had, see your paediatrician promptly and book a developmental check with a Pinnacle clinician.
This is general information, not a diagnosis — a clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre under qualified clinician care.
What to watch
Watch for regression — losing skills she once had: purposeful hand use replaced by repetitive hand-wringing or mouthing, loss of earlier babble or words, slowing head growth, new unsteadiness, or reduced eye contact. A single late milestone alone is usually not this; it is the picture of going backwards that warrants a prompt paediatric review.
Try this at home
Keep a simple note or short videos of what your daughter can do this month — words, pointing, how she holds a toy. If a skill she had clearly disappears rather than just pausing, that record helps your doctor see the pattern quickly.
Trusted sources
Developed by SETU Consortium · Pinnacle Blooms Network · Last reviewed 2026-06-10 · reviewed every 365 days
This is general information, not a diagnosis. A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre, under qualified clinician care.
Frequently asked
Is a single delayed milestone a sign of Rett Syndrome?
Usually not. The hallmark of Rett Syndrome is regression — losing skills your daughter had already mastered, such as purposeful hand use or early words — rather than simply being a little late to reach one milestone. Many children have brief plateaus during illness or growth spurts. It is a clear loss of skills, often with repetitive hand movements, that should prompt a prompt review.
Does Rett Syndrome only affect girls?
It almost always affects girls. It is a rare genetic condition, and the classic pattern is typical early development followed by a slowing or loss of skills, most often between 6 and 18 months. If you notice your daughter going backwards on skills, see your paediatrician promptly.
Can you diagnose Rett Syndrome from a checklist?
No. Rett Syndrome has a genetic basis and is confirmed through medical assessment and testing arranged by a doctor, alongside a clinical developmental evaluation. No online form or checklist can diagnose it. A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre under qualified clinician care.