Fragile X is an inherited condition that causes mental retardation. It is more common and more severe in males but can occur in females too. Early signs include delayed speech and behavioral difficulties and symptoms range from mild learning disabilities to severe mental retardation and autism.
Fragile X is caused by a repeating sequence in a gene on the X chromosome. Carriers have 50 to 200 copies of this sequence (called a “premutation”) and do not have any symptoms. The premutation can expand when it is passed from parent to child. Affected individuals have more than 200 copies of the sequence (a full mutation). All males and approximately half of the females with the full mutation are mentally retarded.
If you have a family history of mental retardation, your care provider may offer you a blood test for Fragile X. If you test positive, you can have a test during the pregnancy (amniocentesis or chorionic villus sampling ) to see if your baby has the disease. If your baby is affected, you can choose to terminate or continue the pregnancy.