Identification of fragile X pre-mutation carriers in the Chinese obstetric population using a robust FMR1 polymerase chain reaction assay: implications for screening and prenatal diagnosis

Challenges in prenatal screening and counselling for fragile X syndrome

“…Their parents will face uncertainty and anxiety about the resulting phenotype, and have a difficult choice to make. Termination of such pregnancy was reported previously and in the study by Cheng et al 1 On the contrary, in the same study, a woman with PM declined prenatal diagnosis owing to the unpredictable phenotype in a FM female. 1 Pre-mutation carriers are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS) and fragile X-associated primary ovarian insufficiency (FXPOI).…”

“…Cheng's team used a specific FMR1 PCR-based assay that could detect CGG repeat numbers up to 1000, allowing the identification of PM and FM. 1 The sensitivity of this PCR test was reported to be high (99%) and the false-positive rate was approximately 1.3% although this was probably overestimated. 1 The cost of the test is US$44, which is not high.…”

“…Although obtaining a maternal blood test for FXS carrier screening is relatively simple, genetic counselling is not, as rightly pointed out by Cheng et al 1 In their study, pre-test counselling was given by a research assistant with a bachelor's and master's degree in human genetics, supplemented by written information. 1 Pre-test counselling for FXS is more difficult than for Down syndrome screening.…”

“…1 Pre-test counselling for FXS is more difficult than for Down syndrome screening. First, an extensive multigenerational family history must be taken to assess whether FXS, developmental, neurodegenerative, or reproductive disability is present in the mother or any of her family members.…”

“…1 It is difficult to counsel these carriers because the risk for CGG expansion, although very low, is uncertain. Thus, prenatal diagnosis may be offered on a caseby-case basis.…”