Prenatal Diagnosis of Chromosome Abnormalities: 21 Years of Experience

Objective: In this study, we aimed to evaluate the demographic data and cytogenetic results of prenatal diagnoses performed in a single genetics laboratory setting over a period of 21 years. Methods: This study is a retrospective analysis of patients who underwent prenatal diagnosis in our center between 2000 and 2021. A total of 2,385 cases between the ages of 18-48 were included in the study. Age, indication, pregnancy week, type of prenatal diagnosis, and the result of cytogenetic analysis of the cases were evaluated. Results: The mean age of the patients was 33.97 ± 4.96 years and 1,205 (50.5%) patients were under 35 years. Amniocentesis was performed in 1,965 (82.4%) patients, chorionic villus sampling in 279 (11.7%) patients, and cordocentesis in 141 (5.9%) patients. A total of 2,114 (88.6%) were normal and 253 (10.6%) were found to have abnormal karyotypes. The most frequently observed abnormal karyotypes were trisomy 21, translocation, and inversion of chromosome 9 (3.6%, 1.4% and 1.0% respectively. The most common indications were: abnormal ultrasonography results in 695 (29.1%), abnormal first trimester test results in 513 (21.5%), and advanced maternal age in 399 (16.7%) patients. The highest positive predictive value for prenatal diagnosis (or abnormal result) was 73.9% for Non-invasive Prenatal Test (NIPT), followed by in paternal chromosome anomaly (17.4%), and an abnormal USG evaluation (14.5%). Conclusion: It is necessary to carry out more studies on NIPT, which has a high positive predictive value, and develop the results for genetic counselling together with conventional and molecular cytogenetic methods.