Chromosomal abnormalities are known as one of the main causes of spontaneous abortions. About 15% of clini­cally recognized pregnancies are aborted before 20 weeks of gestation, and approximately half of these are attributed to detectable chromosome abnormalities [1]. Cytogenetic evaluations of first trimester spontaneous abortions re­vealed an overall incidence of chromosomal abnormalities of 50-70% [2,3]. The most common cause of a spontane­ous abortions is de novo numerical abnormalities, particu­larly autosomal trisomies for chromosomes 13, 14, 15, 16, 21 and 22, followed by sex chromosome aneuploidies and polyploidies [3-5]. The occurrence of chromosomal abnor­malities is also appreciable in spontaneous abortions after in vitro fertilization (IVF). Recent data showed that about 43% of IVF spontaneous abortions are those with chromo­somal abnormalities [6]. The most common applied tech­nique for detection of chromosome abnormalities in spon­taneous abortions is analysis of metaphase chromosomes by karyotyping cultured cells. In fact, the application of fluorescent in situ hybridization (FISH) on uncultured cells has a number of advantages, and has becomes a widely used method for chromosome abnormality detec­tion in spontaneous abortions [7-9].

We have proposed a study of chromosomal abnormali­ties by FISH and an original collection of DNA probes for chromosomes 1, 9, 13, 14, 16, 18, 21, 22, X and Y, as it is known that these chromosomes are involved in most common aneuploidies in spontaneous abortion specimens. Special attention was paid to the use of interphase FISH for identification of mosaic forms of aneuploidies, not properly investigated in spontaneous abortions up to date.