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Chromosome Abnormalities in Human Pregnancy Loss
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
Intriguingly, by comparison with liveborn or stillborn conceptuses, SABs are characterized by a wide variety of chromosome abnormalities, the majority of which involve single missing or extra whole chromosomes (i.e., aneuploidy). The single most-common specific abnormality, sex chromosome monosomy (45,X), accounts for 6.6% of the cases reported in Tables 28.1 through 28.4. Trisomies are the most common class of abnormality, identified in 36.2% of abortuses. Trisomies for all chromosomes have been identified, although a few (e.g., trisomies 1 and 19) are extremely rare. Conversely, other trisomies are quite common, i.e., trisomy 16 is the most commonly identified trisomy and, together with trisomies 15, 21, and 22, these four conditions account for well over one-half of all single trisomies. Importantly, these results are in relatively good agreement with recent studies of human preimplantation embryos from assisted reproduction technology (ART)-derived pregnancies. For example, similar to SABs, chromosomes 15–22 are more likely to be present in an aneuploid state in preimplantation embryos than are larger chromosomes (e.g., [36,37]). Thus, while it is clear that selection eliminates a large number of aneuploid conceptuses between the time of conception and the time of clinical recognition, it also seems likely that certain chromosomes are more likely than others to undergo meiotic mis-segregation.
Recurrent pregnancy loss
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Christine E. Ryan, Danny J. Schust
One aneuploid loss increases the risk of a subsequent aneuploid loss (36). Trisomies are the most common anomaly as a group, led by trisomy 16. Still, the single most common aneuploidy found in first-trimester pregnancy loss specimens is 45 X,0. Some experts therefore suggest that it would be prudent to perform cytogenetic analysis of second and subsequent losses, understanding that a trisomic loss does not increase the risk of recurrent loss (33). In fact, recurrent aneuploidy or polyploidy, though seen with sporadic loss, has not been proven to be associated with recurrent loss when stratified for age (37). If the karyotype of an abortus is found to be aneuploid, a maternal cause for loss can be effectively excluded. The discovery of a legitimate cause for the loss may also be a source of comfort for the grieving family.
The Genetics of Spontaneous Abortions
Published in Howard J.A. Carp, Recurrent Pregnancy Loss, 2020
A maternal age effect is evident in most trisomes, but the relative effect varies among chromosomes. Maternal age correlates positively with errors at meiosis I, the assumed cytological explanation for most autosomal trisomies. The relative proportion of trisomies arising at meiosis I versus those arising at meiosis II varies among aneuploidies. Virtually all trisomy 16 cases are maternal in origin, originating in meiosis I [31]. In trisomies 13 and 21, 90% are maternal, again usually arising at meiosis I. The exception is trisomy 18; two-thirds of the 90% of maternal origin cases originate at meiosis II [32,33]. These data would benefit from contemporary studies because not taken into account is the recent recognition by Kuliev et al. [34] that premature chromatid separation is common during polar body meiosis. Chromatid correction of meiosis I errors may occur in meiosis II. Thus, the proportion of meiosis I errors was only marginally higher (41.7% vs. 35.2) in oogenesis than meiosis II errors; errors in both meiosis I and II can also occur.
Reproductive outcomes in couples with sporadic miscarriage after embryonic chromosomal microarray analysis
Published in Annals of Medicine, 2023
Zhengyi Xia, Ran Zhou, Yiming Li, Lulu Meng, Mingtao Huang, Jianxin Tan, Fengchang Qiao, Hui Zhu, Ping Hu, Qiaoying Zhu, Zhengfeng Xu, Yan Wang
Numerical chromosomal abnormalities were the most frequent abnormal finding, including 542 (48.0%) with aneuploidies and 87 (7.7%) with polyploidies. Among the cases with aneuploidies, 95.4% (517/542) of these cases were identified as single aneuploidies, and multiple aneuploidies composed the remaining 4.6% (25/542). With the exception of chromosomes 1 and 19, single aneuploidies were detected in all chromosomes. Trisomies represented the majority among the cases with single aneuploidies (420/517, 81.2%), and others were monosomies (97/517, 18.8%). With respect to trisomies, trisomy 16 was the most common (142/420, 33.8%), followed by trisomy 22 (64/420, 15.2%) and trisomy 21 (28/420, 6.7%). Monosomies were observed in chromosomes X (95/97, 97.9%), 8 (1/97, 1.0%) and 21 (1/97, 1.0%). Among the cases with polyploidies, 85 (97.7%) were triploidy and two (2.3%) were tetraploidy. In addition, four cases (0.4%) with whole-genome UPD were identified in our cohort.
Confined placental trisomy detection through non-invasive prenatal testing: benefit for pregnancy management
Published in Journal of Obstetrics and Gynaecology, 2020
Jun-Hui Wan, Ping He, Li-Li Xu, Dong-Zhi Li
UPD for the majority of chromosomes is without phenotypic effect except threefold: imprinting disorders, homozygosity for a recessive variant in a single parental chromosome, and placental or foetal mosaicism (Eggermann et al. 2015). Thus far, only five chromosomes have been defined as imprinted: chromosomes 6, 7, 11, 14, and 15 (Mackay and Temple 2017). Therefore, for a pregnancy with a foetal UPD other than the five imprinted chromosomes, such as the UPD (16) in the present case, concerns might be the CPM with or without hidden trisomy mosaicism in the foetus and autosomal-recessive diseases. Trisomy 16 usually results in a spontaneous miscarriage in the first trimester (Creasy et al. 1976). However, a small proportion of such conceptions survive as a diploid embryo, either with or without UPD, thus resulting in CPM with a normal foetal karyotype (Wolstenholme 1995). Both maternal and foetal adverse consequences can complicate CPM pregnancies, including gestational hypertension or preeclampsia, intrauterine growth restriction (IUGR), congenital anomalies, preterm delivery, caesarean delivery, intrauterine foetal death or perinatal death, and NICU admission (Sparks et al. 2017; Toutain et al. 2018). Therefore, a prenatally identified CPM pregnancy should be subjected to intensive surveillance for both the mother and foetus, as evidenced by this case.
Early Pregnancy Losses: Review of Nomenclature, Histopathology, and Possible Etiologies
Published in Fetal and Pediatric Pathology, 2018
M. Halit Pinar, Karen Gibbins, Mai He, Stefan Kostadinov, Robert Silver
Among chromosomal abnormalities in early pregnancy losses, 86%–91% are numerical chromosomal abnormalities, which can be subdivided into aneuploidy (trisomies and monosomies) and polyploidy. Increasing maternal age increases risk for aneuploidy and, indeed, increases the risk for miscarriage. Risk of early pregnancy loss ranges from 8.9% in women ages 21–25 years to 74.7% in women older than 45 years (45). Trisomies are the most frequently occurring numerical chromosomal abnormalities (52%–63%), followed by polyploidy (17%–21%) and monosomy X (11%–13%) (8,46). Most trisomies occur as a consequence of nondisjunction during maternal meiosis I. Trisomy 16 is the most common trisomy in pregnancy loss specimens, followed by trisomies of 22, 15, and 21 (9). Monosomy X is also common and usually occurs as a result of paternal sex chromosome loss. Autosomal monosomies are less common than monosomy X (2).