Detection of low level sex-chromosomal mosaicism

In this report we present the cytogenetic findings of low frequency (X or Y)-mosaicism (1.0%-3.6%) in six patients aged between 28 and 36 years (average age 32.17) among sixteen individuals (analysis of 5402 mitoses) referred for genetic counseling after unsuccessful assisted reproductive treatment. For the detection of low level mosaicism, analysis of 500 metaphases is necessary to prove the presence of 1% abnormal clones, if the "background" level of the same aberraitons in controls is 0.1%. Low frequency mosaicism of sex chromosomes may be responsible for the unsuccessful results of in vitro fertilization and related techniques. The question may be raised whether diagnosis in subsequent pregnancies is indicated in these patients.