Trisomy 21 and Assisted Reproductive Technologies: A review

Trisomy 21 is the most common genetic disorder seen among infants, and it causes spontaneous abortions, abnormal neural development and other pathologies associated with newborn development. In newborns with this trisomy, 90-95% have full trisomy, 1.4-1.9% have mosaicism, and 1-4.7% have translocations. The principal cause of trisomy 21 is advanced maternal age, in which recombination errors may occur during fetal development, age-related accumulation of damaged DNA, cohesin degradation producing the premature loss of chromosomes or sister chromatids, and alterations during the spindle formation process. The paternal age has also an effect on trisomy 21, specifically during male aging, when there is higher risk of chromosomal breaking in spermatozoa. Epigenetics is also an important risk factor of trisomy 21 through changes in the DNA methylation process, histone modification and non-coding RNAs. Assisted reproductive technologies (ART) have emerged in recent years as a safe alternative for couples with fertility problems. These techniques, which include controlled ovarian stimulation (COS), in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and vitrification, decrease the incidence of aneuploidy in human preimplantation embryos, and are widely used. The following study aims to review and discuss the available literature on trisomy 21 in the field of assisted human reproduction.