ACOG committee opinion. No. 338: Screening for fragile X syndrome.

Fragile X syndrome is the most common inherited form of mental retardation, affecting approximately 1 in 4,000 males and 1 in 8,000 females. DNA-based molecular analysis is the preferred method of diagnosis for fragile X syndrome and its premutations. Prenatal testing for fragile X syndrome should be offered to known carriers of the premutation or mutation. Testing for fragile X syndrome should be considered for any child with developmental delay of uncertain etiology, autism, or autistic behavior or for any individual with mental retardation of uncertain etiology. Women with ovarian failure or an elevated follicle-stimulating hormone level before 40 years of age without a known cause should be screened to determine whether they have the fragile X premutation.