Collaborative prospective study of the fragile X syndrome: request for participation

A collaborative prospective study of the fragile X syndrome (fra[X]) has been initiated to refine the estimates of the recurrence risks based on the phenotype of the mother and the family history of the syndrome. The basic unit of data consists of the description of the pregnancy outcome of women known to carry the fra(X) mutation or who are mothers of a fra(X)-positive son. Pregnancy outcome includes both prenatal diagnoses and live-borns. The prospective nature of the data eliminates problems of ascertainment and thereby provides more accurate estimates. The specific aims of the study are both clinically and research oriented: 1) refine the estimates of recurrent risks based on the phenotype of the mother and on family history for use in genetic counseling; 2) determine if recurrence risks depend on the phenotype of the carrier parent; 3) determine if a proportion of affected individuals is due to new mutations; and 4) determine the reproductive fitness of fra(X) carriers. This paper describes the rationale behind this study, the data to be collected, and the sample sizes necessary to test hypotheses. Most importantly, participation in this collaborative study is requested from all professionals who work with the fra(X) syndrome.