Cytogenetics of human oocytes, zygotes, and embryos after in vitro fertilization

Abstract

Chromosome errors, inherited or arising de novo during gametogenesis and transmitted at fertilization to the conceptus, may be a major cause of embryonic mortality. The in vitro fertilization and embryo transfer (IVF/ET) procedure provides extra material--oocytes, zygotes, and embryos--to investigate the contribution of chromosomal abnormality to implantation failure. This paper reviews the results of cytogenetic studies on such material. Estimates from a total of 1120 oocytes from 11 studies give an overall proportion of chromosomal abnormality of 35%. Single and multiple nullisomies and disomies are found, involving nonrandom chromosome gain or loss. Hypohaploid complements are more frequent than hyperhaploid complements. The higher rate of chromosome loss of hypohaploid karyotypes was found to be largely artifactual. The estimated overall frequency of aneuploidy is 13%. In embryos the level of chromosomal abnormality is 23%-40%. Errors of fertilization are responsible for a substantial number of triploid embryos, many of which develop into mosaics. Factors extrinsic to the conceptus, such as infertility, advanced maternal age, and ovarian hyperstimulation, may increase the level of chromosomal abnormality. More refined methods for accurately recognizing and selecting chromosomally normal embryos for transfer are needed to improve the success rate of this reproductive technology.

Preimplantation Genetic Testing of Aneuploidy by Next Generation Sequencing: Association of Maternal Age and Chromosomal Abnormalities of Blastocyst

“…The chromosome most affected by age is chromosome 14; the data show that the rate of multiple deviations increased by 3.7 times in the elderly group (≥ 37 years). Then came chromosome 7, the rate of multiple deviations increased by 3.3 times and chromosome 18 increased by 2.9 times when the mother's age increased compared with the average increase of about 1.5 to 2 times for all chromosomes 2, 3, 12, 13, 15, 17, 18, 19, 20, 21, 22. In addition to the study of Alfarawati and colleagues in 2011, chromosomes 7 and 14 were the most prevalent group with the highest increase in maternal age (5-6 times higher), and for infection chromosomes 2, 15, 17, 20, 22 doubled [17]. This conclusion is quite similar to our results, thus confirming the reliability of this study.…”

“…This number indicated with Rubio's study in 2003 analyzing similar maternal age that there were 45.1% embryo had abnormal chromosomal [16]. In 2003, Alfarawati showed that there was more than half of embryos tested had abnormal (56.7%) [17]. However, their study focused on recurrent miscarriage and high maternal age (average 37.5 years) whereas this study focused on patient had average age lower (34.4 years).…”

“…Chromosomes 7 and 18 displayed a 3.3 and a 2.9-fold increase, respectively. For chromosomes 2, 3,12,13,15,17,19,20,21 and 22 the increase was around from 1.5 to 2-fold. Other chromosomes were found little or no change in aneuploidy rate with advancing age (Figure 2).…”

Morphological, cellular and molecular changes during postovulatory egg aging in mammals

“…1 ). Further, postovulatory aging triggers premature chromosome separation, chromosomal dispersion and decondensation, clumping of chromosome and chromatid separation in eggs [ 4 , 46 , 47 ] that could lead to epigenetic changes in offspring [ 23 , 48 ].…”

Rapid-prenatal diagnosis through fluorescence in situ hybridization for preventing aneuploidy related birth defects

“…[456] The most common cause of spontaneous abortion is numerical chromosome imbalances (aneuploidies), particularly of chromosomes 13, 14, 15, 16, 18, 21, 22, and X. [789] Aneuploidies of five particular chromosomes (13, 18, 21, X, Y) accounts for 95% of the chromosomal aberrations that lead to infants born with congenital defects. [10] Therefore, it is essential in prenatal diagnostics to analyze chromosomal abnormalities by utilizing procedures such as amniocentesis and chorionic villus sampling (CVS) for early detection of potential birth defects, particularly in high risk pregnancies.…”