Skip to content
Diagnosing Fragile X in Children

Diagnosing Fragile X in Children

Fragile X syndrome is the most common cause of autism known to medical practitioners. This syndrome is a genetic condition resulting in intellectual disability affecting more boys than girls. Early diagnosis and treatment can help your child live a full life and reach their potential.

SpecialKids.Company autism fragileX

The cause of Fragile X

Fragile X syndrome occurs when the FMR-1 (Fragile X mental retardation) gene is damaged. This gene is considered important for your child’s early development but when the gene experiences an alteration in its length, your child’s chances of developing Fragile X syndrome become greater.

Inheriting the Fragile X Gene

Fragile X is carried on the X chromosome in either the father or the mother of a child. The more the gene is passed on down the generations, the more Fragile X mutation occurs and lengthens the gene. This is known as “genetic anticipation” . If a parent is a Fragile X carrier, any offspring will only develop Fragile X Syndrome if a certain number of repeats and gene lengthening have occurred throughout the generations.

Testing for Fragile X during pregnancy

As a mum-to-be, you can have prenatal tests done to determine if your baby has Fragile X syndrome. The three prenatal tests available for testing Fragile X syndrome in pregnancy are the following:

  • Chronic villi sampling (CVS) is the least common form of testing. It involves removing a small amount of fetal tissue when you are 9 to 11 weeks pregnant
  • Amniocentesis is commonly available and can be done after you have reached 15 to 18 weeks in your pregnancy. With amniocentesis, a small sample of amniotic fluid is tested for the FMR1 mutation. The results of the amniocentesis take about 2 to 4 weeks, in order for the cells to grow and be analysed for Fragile X.
  • Percutaneous umbilical blood sampling (PUBS) is considered to be the most accurate form of prenatal testing. Often PUBS is used to confirm CVS or amniocentesis results. You can only use PUBS testing after you have reached 18 to 22 weeks in your pregnancy in order to reduce the risk of miscarriage.

Diagnosing children with Fragile X

It is never too late to find out if your child has Fragile X. Testing for Fragile X can happen at any point in your child’s childhood or adulthood. The earlier Fragile X syndrome can be diagnosed, the earlier treatment can begin. The average age for children to be diagnosed with Fragile X syndrome is between the ages of 3 years (for boys) and 3 and a half-years (for girls).

SpecialKids.Company autism fragileX

Your local GP can arrange for your child to have a DNA blood test or recommend a clinical geneticist for a genetic test for Fragile X syndrome.When it comes to diagnosing for Fragile X, developmental delays are the first symptoms parents’ notice. This includes delayed speech and language development, difficulties with emotions or social settings, sensory sensitivity, delayed development in gross motor skills and fine motor skills.

 Useful Resources

Fragile X Syndrome – A guide to assessment and diagnosis

National Human Genome Research Institute – Learning about Fragile X Syndrome

All about Fragile X Syndrome

Fraxa Finding a Cure for Fragile X – DNA Testing for Fragile X is widely available

Medscape - Fragile X Syndrome



Previous article Pacifier and Bottle Weaning for Children with Autism