FMR1 CGG allele size and prevalence ascertained through newborn screening in the United States

Blood spot screening of 14,207 newborns (7312 males and 6895 females) was conducted in three birthing hospitals across the United States beginning in November 2008, using a PCR-based approach.The prevalence of gray zone alleles was 1:66 females and 1:112 males, while the prevalence of a premutation was 1:209 females and 1:430 males. Differences in prevalence rates were observed among the various ethnic groups; specifically higher frequency for gray zone alleles in males was observed in the White group compared to the Hispanic and African-American groups. One full mutation male was identified (>200 CGG repeats).The presented pilot study shows that newborn screening in fragile X is technically feasible and provides overall prevalence of the premutation and gray zone alleles in the USA, suggesting that the prevalence of the premutation, particularly in males, is higher than has been previously reported.