Prenatal diagnosis of chromosomal disorders in North-West Russia: a survey of 3440 cases

Abstract

Objective: our original strategy for PD of chromosome disorders includes analysis of direct chromosome preparations from CVS as the basic step, supplemented with CBL cultures for karyotyping of the fetuses with abnormal or ambiguous CVS results.

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Methods: 3440 cases of cytogenetic PD were performed since 1987, most of them (87%) were represented by CVS. Standard karyotyping with direct chromosome preparations, differential staining (QFH/AcD, QFH/ MG), and semiautomatic system for image analysis (ISTA-Video Test, St-Pb) was applied throughout the study. Conventional analysis was supplemented by FISH and molecular genetic techniques if necessary.

Results: Success rate of cytogenetic analysis was 98,8% (CVS II) - 99,3% (CVS I, CBL). Altogether 199 fetuses with chromosome aberrations (5.8%) including 86 heteroploids were found. Out of a total 42 mosaics, only 4 were provided as true ones, and 29 could be attributed to CPM of the type 1. Karyotype discrepancies between CVS and fetal tissues were confined to 3 cases including 1 false-positive case. Not a single false-negative diagnosis was recorded so far.

Conclusion: Our karyotyping strategy (direct CVS preparations supplemented with CBL, FISH and PCR) is quite sufficient for reliable PD of chromosome disorders.