The chromosomal challenge of human embryos: prevalence of aneuploidy and mosaicism

Abstract

Chromosomal aberrations, such as whole-chromosome aneuploidies, segmental aneuploidies, whole-chromosome mosaicism, and segmental mosaicism, are key factors influencing embryonic development and the outcomes of fertility programs. This analytic review critically examines the prevalence and origins of these genetic abnormalities, emphasizing the significant maternal contribution to whole-chromosome aneuploidies and the age-related nature of these aberrations. In contrast, segmental aneuploidies, whole-chromosome mosaicism, and segmental mosaicism appear largely age-independent and show considerable variability across studies, mainly due to technical artifacts and methodological differences. By analyzing the accumulated data, scrutinizing methodological discrepancies in preimplantation genetic testing for aneuploidies, and distinguishing between biologic phenomena and artifacts, this review aims to clarify the current understanding of chromosomal aberrations in human embryos and their impact on reproductive health.