The need to reevaluate trisomy screening for advanced maternal age in prenatal diagnosis

OBJECTIVES: Fluorescence in situ hybridization aneuploidy screening promises immediate results. To evaluate aneuploidy screening in prenatal diagnosis, the prenatal records at Oregon were reviewed. STUDY DESIGN: Karyotype reports of 7240 amniocentesis samples referred for advanced maternal age were retrospectively reviewed for numeric and structural chromosome abnormalities. RESULTS: The frequency of abnormal karyotypes was 2.5%; 1.4% were age-related trisomies and sex-chromosome aneuploids, and 1.1 % were non-age-related abnormalities. The incidence of structural rearrangements was 0.9%, of which 70% were familial but not suspected on the basis of family history. CONCLUSIONS: Structural chromosome abnormalities were twice as common as previously reported, representing a significant unrecognized risk for subsequent pregnancies and other family members. Fluorescence in situ hybridization aneuploidy screening would not routinely detect structural chromosome abnormalities, which were twice as frequent as numeric aneuploidy at age 35 years. Routine use of fluorescence in situ hybridization for prenatal diagnosis should not be adopted without a prospective study of its accuracy, reliability, and impact on prenatal diagnosis.