Cytogenetic evaluation of 661 prenatal samples

Purpose: Fetal karyotyping is commonly used to detect chromosomal abnormalities in high-risk pregnancies. Our study is intended to evaluate the results of fetal karyotyping performed in our laboratory for six years and to determine the frequency of chromosomal abnormalities, thus revealing their clinical significance. Materials and Methods: The cytogenetic results of 661 prenatal samples with an indication for invasive prenatal procedures (amniocentesis, cordocentesis) who had a chromosome analysis and FISH testing between February 2013 and March 2019 were analyzed in our study. Results: A total of 72 (10.8%) abnormal fetal karyotypes were observed in the study group. Trisomy 21 was the most common numerical aberration (29%, n = 23), followed by trisomy 18 (16%, n = 13), trisomy 13 (2.6%, n = 2), triploid (2.6%, n = 2), sex chromosome aneuploidies (5.2%, n = 4), and rare mosaic autosomal aneuploidies (2.6%, n = 2). Inversions (16%, n = 13), inherited translocations (7.8%, n = 6), unbalanced/de novo translocations (6.5%, n = 5), deletions (5.2%, n = 4), additional chromosomes (1.3%, n = 1), isochromosomes (1.3%, n = 1), and derivative chromosomes (1.3%, n = 1) were identified as structural abnormalities. Of the 18 cases that underwent FISH testing, trisomy 18 was detected in 1 case and tetrasomy 12p was detected in 1 case. Conclusion: Fetal karyotyping is still an effective and valuable method in the diagnosis of fetal anomalies and provision of effective genetic counseling. In addition, fetal karyotyping should be supported by complementary methods and advanced technologies for accurate and rapid prenatal genetic diagnosis.