Fragile X Allele Testing: When Is Prenatal Testing Indicated?

These study results suggest that invasive prenatal diagnosis (typically by amniocentesis) to detect fragile X syndrome in the fetus is warranted only in pregnant women with fragile X alleles containing ≥55 CGG repeats.

Fragile X is the most common inherited cause of mental retardation, and DNA analysis of the fragile X allele is possible now. The mutation is complex, involving an unstable CGG trinucleotide sequence in the FMR1 gene on the X chromosome that can expand from generation to generation. Normal individuals typically have fewer than 45 CGG repeats. Women with large numbers of CGG repeats (>200) are most likely to have offspring with neurologic problems and retardation.

In this study, researchers evaluated findings from nearly 15,000 women (age, ≥18) and from 238 mother–offspring pairs. Mutations were found in 1 in 3.5 women with family histories of fragile X and in 1 in 10 with premature ovarian failure. In contrast, 1 in 86 with family histories …

Reviewing Author

Robert W. Rebar, MD

Disclosures

Consultant/Advisory BoardMyovant Sciences, Inc.

Editorial BoardsEndoText; Clinical OB/GYN Alert

Leadership Positions in Professional SocietiesAmerican Society for Reproductive Medicine (Member, Ethics Committee)

Robert W. Rebar, MD

Disclosures

Consultant/Advisory BoardMyovant Sciences, Inc.

Editorial BoardsEndoText; Clinical OB/GYN Alert

Leadership Positions in Professional SocietiesAmerican Society for Reproductive Medicine (Member, Ethics Committee)