Results of carrier screening and prenatal diagnosis for FMR1 gene in 819 cases

OBJECTIVE To determine the carrier rate of Fragile X mental retardation 1 gene (FMR1) mutants in women with a history of adverse pregnancy or childbirth, and to provide prenatal diagnosis for the carriers. METHODS Peripheral blood samples were collected from women with a history of adverse pregnancy or childbirth, and the FMR1 gene cytosine-guanine-guanine repeat number (CGG)n was determined by triple-repeat primer polymerase chain reaction (TP-PCR) combined with capillary electrophoresis. Prenatal diagnosis was provided for the carriers during pregnancy. RESULTS Among 819 samples, 9 gray zone repeats carriers and 10 premutation carriers were detected, which gave a prevalence of 1 in 91 and 1 in 82, respectively, with a total prevalence of 1 in 43. Prenatal diagnosis was provided during 7 pregnancies for 6 carriers. A female fetus with premutation (n = 30/57) and an affected male fetus with full mutation (n = 336) were detected. CONCLUSION FMR1 gene testing in women with a history of adverse pregnancy or childbirth can facilitate genetic counseling and reproductive guidance for carriers of gray zone repeats and premutations. Prenatal diagnosis for carriers of premutation can facilitate reduction of the birth of children with fragile X syndrome.