Recent experience in prenatal diagnosis of fragile X

Our experience with 48 prenatal fragile X cases (35 amniocenteses; 13 chorionic villi samplings) is summarized. Of these 48 cases, 18 consultands were known to be carriers of fragile X. No cytogenetic false negatives or positives were identified but 2 cases were uninterpretable. Cytogenetic recommendations include: 1) Ten or more days recovery time after growth in Chang medium, and 2) use of 3-4 media/inducer systems with duplicate harvests. Direct DNA probe testing will likely be the method of choice for prenatal diagnosis after sufficient data are collected to verify interpretation. Until then, both cytogenetic and direct DNA techniques should be utilized.