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Preimplantation Genetic Testing for Aneuploidies: Where We Are and Where We're Going
Published in Darren K. Griffin, Gary L. Harton, Preimplantation Genetic Testing, 2020
Andrea Victor, Cagri Ogur, Alan Thornhill, Darren K. Griffin
Polar body (PB) biopsy was first introduced to identify oocytes that carry disease alleles in women heterozygous for a genetic disease [20]. Polar bodies are the byproducts of meiosis I and II, and their biopsy is not likely to impact negatively on an embryo's future development. Polar bodies may be removed either one at a time or simultaneously following fertilization [21], but because they might undergo rapid fragmentation, any delay in biopsy could result in misdiagnosis or no result. The primary advantages of polar body biopsy are that it is less invasive than other forms and it inherently creates a greater time window for analysis when performing transfer for a fresh cycle. Disadvantages lie in the fact that polar bodies cannot be used to detect paternal chromosomes or post-zygotic errors. Consequently, polar body biopsy is limited in PGT-A to the diagnosis of meiotic abnormalities and translocations of maternal origin. Polar body biopsy gained popularity when it was proposed as an alternative to cleavage-stage biopsy [22,23], which, after randomized controlled trials (RCTs) [15,24] , limited the applicability of PGT-A. Indeed, the first successful live birth following 24-chromosome screening was performed following polar body biopsy [25].
Preimplantation Genetic Screening
Published in Botros Rizk, Yakoub Khalaf, Controversies in Assisted Reproduction, 2020
M. Yusuf Beebeejaun, Sesh K. Sunkara
As part of PGS, polar body biopsy is significantly useful in countries where biopsy of an embryo is not permitted. In these situations, genetic analysis of polar bodies offers an alternative to assess the genetic composition of an embryo, based on the predictive nature of the genetic composition of the oocyte.
Human embryo biopsy procedures
Published in David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham, Textbook of Assisted Reproductive Techniques, 2017
Jason Kofinas, Caroline Mccaffrey, James Grifo
Polar body biopsy in humans was first described in 1990 (8). The procedure was developed in an effort to decrease the invasive nature of EB since the polar body(ies) is already separated from the embryo and will not contribute to the developing embryo. Removal of the first polar body (PB1) or both the first (PB1) and the second polar body (PB2) requires creating a hole in the zona pellucida (ZP) and removing the PB1 possibly prior to fertilization or the removal of both polar bodies after fertilization. The genetic material in PB1 is only representative of the DNA in the oocyte (maternal contributions) and specifically only maternal DNA that is not included in the embryo. For this reason, polar body biopsy is particularly useful for detecting maternally inherited monogenic diseases and for numerical/structural chromosomal aberrations in the oocyte (9).
Reproductive outcomes of infertile couples undergoing assisted reproductive technology who are carriers of chromosomal abnormalities: a retrospective cohort study
Published in Annals of Medicine, 2022
Ling Cui, Fang Wang, Yonghong Lin, Min Li
Genetic counselling and discussion of possible preimplantation genetic testing should be offered when a structural rearrangement (translocation, inversion, deletion, or insertion) is discovered in a parent. Because of these limitations, confirmation of preimplantation genetic testing–structural rearrangement results by means of chorionic villus sampling (CVS) or amniocentesis should be offered [16]. However, the evidence suggests that universal use of PGT‐A is premature. We know that the technology is imperfect: PGT‐A can erroneously call euploid embryos aneuploid [17] and we do not know what to do with apparently mosaic embryos [18]. Blockeel et al. showed that preimplantation genetic screening does not increase the implantation rates after IVF-intra-cytoplasmic sperm injection in women with repeated implantation failure [19]. Some studies have failed to show improvements in live birth rates for women younger than 37 years of age [20–22], so it seems unlikely that the added complexity and cost of this intervention can be justified in younger patients. An economic analysis of preimplantation genetic testing for aneuploidy by polar body biopsy in woman of advanced maternal age showed that PGT-A greatly increased the cost and suggested that patients and doctors need to be aware of the high-cost implications of applying PGT-A [23].
Management of a multiple endocrine neoplasia type 1 during pregnancy: a case with primary hypertension
Published in Gynecological Endocrinology, 2022
Jianyi Li, Dabao Xu, Xinli Liu
Advances in molecular biology and genetics have been favoring clinical diagnosis and possible therapies. In recent years, preimplantation genetic diagnosis (PGD) enables such patients to select unaffected embryos for transfer. Currently, there are three potential methods DNA collecting: first or second polar body biopsy, blastomere biopsy from 6- to 8-cell cleaving embryos, trophectoderm biopsy from blastocyst on the fifth or sixth day of development [10]. To our knowledge, there have been only one case published about the preimplantation genetic diagnosis for a patient with MEN 1 [11]: a 34-year-old male patient, carrier of MEN 1 syndrome, the couple underwent a cycle of controlled ovarian stimulation and intracytoplasmic sperm injection, embryos were biopsied at the blastocyst stage and cryopreserved, PCR-based DNA analysis was used for PGD testing, only one in five embryos was unaffected, this embryo was transferred and clinical pregnancy was confirmed, a healthy infant was born. This case offers a new way for patients with MEN 1 syndrome. As spontaneous pregnancy, amniocentesis is suggested for testing MEN 1 germline mutation in China, if the mutation is detected, the patient can choose artificial abortion. Our patient refused amniocentesis or postnatal DNA test.
Preimplantation genetic diagnosis (PGD) and genetic testing for aneuploidy (PGT-A): status and future challenges
Published in Gynecological Endocrinology, 2020
Romualdo Sciorio, Luca Tramontano, James Catt
Since the 1980s, the method for embryo biopsy has been on day-3. Usually one or two blastomeres were aspirated and used for diagnosis [2]. The first method applied to breach the zona pellucida (ZP) was the acid tyrodes solution (pH 2.7) with subsequent aspiration of the cell(s). A shift was introduced with the use of a laser for ZP drilling [26] and the use of calcium magnesium free media, which allows an easier blastomere removal and a shorter time to perform the biopsy [27]. Polar body biopsy (PBB) as a less invasive alternative method was first introduced by Verlinsky et al. [28]. The fertilized oocyte will release the second polar body that contains the mirror image of the maternal genetic material in the embryo. The disadvantages of PBB are that only the maternal aneuploidies can be identified, therefore, it cannot be applied if the male carries a chromosome abnormality [28]. On the other hand, a benefit of the PBB is the fact that it can be performed soon after oocyte retrieval. Results can be available within two days, and fresh embryo transfer can be applied. In 2012, the ESHRE started a multinational, multicenter, randomized clinical trial to assess the effectiveness of PGT-A performed with the PBB by microarray analysis. The main question of the study was to evaluate whether the analysis of 23 chromosomes in the PB1 and PB2 and the selection of euploid embryo for transfer increases the change of a live birth within one year among women aged 36-40 years, compared to ICSI without chromosome analysis. Between June 2012 and December 2016, 205 consenting women were assigned to ICSI treatment with PGT-A (study group) and 191 to ICSI without PGT-A (control group). The results reported that the proportion of women with a live birth was similar between the two groups: 50 of the 205 with chromosome screening (24.4%) versus 45 of 191 without chromosome screening (23.6%) and it was accepted that PGT-A performed with the PBB biopsy will not increase live birth rates [29].