Aim of study: Analysis of incidence of chromosomal abnormalities and variants in foetuses karyotyped because of the advanced maternal age.
Type of study: A retrospective epidemiological study of results of cytogenetic examinations followed amniocentesis in 418 foetuses.
Material and methods: In our study we have used data from archives of the Cytogenetic laboratory of the Institute of Biology and Medical Genetics of the First Faculty of Medicine, Charles University and General Teaching Hospital in Prague. We have included only the cases where the amniocentesis was performed solely because of advanced maternal age. All cases were divided in specific groups and analyzed.
Results: There were totally 1107 karyotype examinations following the amniocentesis between 2007 and 2009 in our laboratory. Among these cases, 418 amniocenteses (37.8%) were performed only because of the advanced maternal age. The mean maternal age in this group was 38.02 +/- 2.4 years. In the whole group of 418 foetuses, 256 of them (61.24%) had normal karyotype, without chromosomal variants or pathologies. In 9 cases (2.15%) we identified pathologic karyotype. Down syndrome was identified in 3 cases (0.72%), what means one case of Down syndrome per 139 amniocenteses performed because of the advanced maternal age. Among other pathologies there were three (0.72%) gonosomal aneuploidies. Variants of acrocentric chromosomes were identified in 121 (28.95%) foetuses, variants of heterochromatine regions in 53 (12.68%) foetuses and other karyotype variants in one case (0.24%). In some cases, we have identified coincidence of more than one chromosomal variant and/or pathology.
Conclusion: Our study presents the overview of chromosomal pathologies and variants that can be identified in fetal karyotype examinations because of the advanced maternal age. The efficiency of Down syndrome identification did not differ from the overall efficiency of amniocentesis in the Czech Republic. Advanced maternal age is still considered as an important part of the indication criteria for invasive prenatal diagnosis.