engleski

Unexpected sturctural chromosome abnormalities in 4100 prenatal diagnosis in Yugoslavia

The aim of this study was to establish the incidence rates of unexpected structural chromosome abnormalities in our series of 4100 prenatal diagnosis performed in patients who were considered to be at substantial risk of having a chromosomally abnormal fetus. To avoid possible ascertainment bias resulting form selective study of translocation carriers, we excluded results of 1472 fetuses whose parents had a known or suspected risk of structural chromosome abnormality (translocation carriers, previous offspring with chromosome abnormality, previous spontaneous abortions etc.). The primary analysis was done upon the remaining subgroup of 1:164 prenatal cytogenetic diagnosis an unsuspected chromosome abnormality was discovered. The observed rate was 6.1% ; 0.8% were unbalanced and 5.3% balanced. The rate of mutants was 1.9% (0.4% for unbalanced and 1.5% for balanced abnormalities). A rather low incidence of structural chromosome abnormalities was found in high risk pregnancies, excluding translocation carriers (4.3%). Comparing our data with the derived rates of unsuspected structural chromosomal abnormalities in French, Danish and extensive USA studies, we did not find significant difference between rates, in spite of sample size variations, geographical, racial and possible environmental (clastogenic) factors that could generate balanced and unbalanced structural chromosome aberrations in certain populations, as it was suggested by Young et al. in 1984.

structural chromosme abnormalities; prenatal diagnosis

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