Objective: Analysis of data from prenatal cytogenetic studies performed during 10 years. Design: Retrospective analysis of cytogenetic results. Setting: Cytogenetic laboratory, Department of Clinical Genetics GENNET, Prague. Methods: Cytogenetic analysis of cultivated amniotic cells. Results: 180 chromosomal pathologies, including 110 numerical and 70 structural, were diagnosed in 5743 samples of amniotic fluid. Relatively high number of structural aberrations was found also in groups of patients examined because of increased maternal age, abnormal values of bio- chemical markers and abnormal ultrasound findings. Chromosomal abnormalities in individual groups of patients, risk figures for de novo balanced structural aberrations, additional marker chromosomes and some mosaic findings as the management following the prenatal diagnosis of this abnormalities are discussed. Conclusion: On the basis of the great number of familiar structural aberrations in our material is recommended to pay attention to the detection of such anomalies also in groups of patients where numerical chromosomal changes are namely expected.

        Key words: prenatal cytogenetic diagnosis, numerical and structural chromosomal aberrations