Clinical outcomes following preimplantation genetic testing and microdissecting junction region in couples with balanced chromosome rearrangement

PurposeThe purpose of this study is to summarize the clinical outcomes of apparently balanced chromosome rearrangement (ABCR) carriers in preimplantation genetic testing (PGT) cycles by next-generation sequencing following microdissecting junction region (MicroSeq) to distinguish non-carrier embryos from balanced carriers.MethodsA retrospective study of 762 ABCR carrier couples who requested PGT for structural rearrangements combined with MicroSeq at the Reproductive and Genetic Hospital of CITIC-Xiangya was conducted between October 2014 and October 2019.ResultsTrophectoderm biopsy was performed in 4122 blastocysts derived from 917 PGT-SR cycles and 3781 blastocysts were detected. Among the 3781 blastocysts diagnosed, 1433 (37.9%, 1433/3781) were balanced, of which 739 blastocysts were carriers (51.57%, 739/1433) and 694 blastocysts were normal (48.43%, 694/1433). Approximately 26.39% of cycles had both carrier and normal embryo transfer, and the average number of biopsied blastocysts was 6.7. In the cumulative 223 biopsied cycles with normal embryo transfer, all couples chose to transfer the normal embryos. In the 225 cycles with only carrier embryos, the couples chose to transfer the carrier embryos in 169/225 (75.11%) cycles. A total of 732 frozen embryo transfer cycles were performed, resulting in 502 clinical pregnancies. Cumulatively, 326 babies were born; all of these babies were healthy and free of any developmental issues.ConclusionOur study provides the first evaluation of the clinical outcomes of a large sample with ABCR carrier couples undergoing the MicroSeq-PGT technique and reveals its powerful ability to distinguish between carrier and non-carrier balanced embryos.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10815-020-02052-6.     

The application of PGT-A for carriers of balanced structural chromosomal rearrangements

Abstract

The aim of this study was to analyze differences in chromosomal aberrations and euploidy in embryos of each translocation type and gender of carrier in the case series of 10 couples with balanced translocations who underwent IVF with embryos trophectoderm (TE) biopsy and PGT-A to detect chromosomal aberrations. This is a Case Series (Retrospective study). In each case, controlled ovarian hyperstimulation, oocyte insemination with intracytoplasmic sperm injection (ICSI) and cultivation gave multiple blastocysts, that underwent trophectoderm (TE) biopsy with PGT-A analysis using aCGH and NGS. Number of total unbalanced translocations compared to the number of sporadic aneuploid embryos was 39.6% to 39.6% (50% to 50% of all 37 aneuploid embryos). The highest euploidy rate was in male carrier group – 26.7% and the lowest in the Robertsonian translocation carrier group – 18.2%. Sporadic aneuploidy – 68.2% was highest in Robertsonian translocation carrier group and lowest in female group – 11.1%. Chromosomal aberrations related to translocation were highest in female carrier group – 77.8% and lowest in Robertsonian translocation carrier group – 13.6%. Our study showed that expectancy of total embryo aneuploidy rates will be higher in carriers, than in people with normal karyotype. The prevalence of chromosomal aberrations related to translocation was 4.5 times higher in Reciprocal carrier group than in Robertsonian translocation carrier group. Among maternal and paternal carrier groups, the embryos from female carriers had the lowest euploidy rate, unbalanced translocation rate 4.7 times higher than in the male carrier group and higher total aneuploidy rates.     

Prenatal finding of a fetus with mosaicism for two balanced de novo chromosome rearrangements

Karyotyping of a fetus with mild cerebral ventriculomegaly detected with ultrasound at 23 weeks revealed two apparently balanced structural rearrangements in mosaic form. Using conventional cytogenetics and FISH, the chromosomal constitution was identified as 46,XX,t(3;10)(p13;q21.1),inv(6)(p23q12)/46,XX. A 46,XX chromosome constitution was predominantly present in the skin whereas in the fetal blood the cell line with two balanced chromosome rearrangements was selectively retained. To the best of our knowledge this is the first prenatal case of mosaicism for two de novo balanced structural chromosome rearrangements to be reported.     

Genetic counselling and ethical issues with chromosome microarray analysis in prenatal testing

Molecular karyotyping using chromosome microarray analysis (CMA) detects more pathogenic chromosomal anomalies than classical karyotyping, making CMA likely to become a first tier test for prenatal diagnosis. Detecting copy number variants of uncertain clinical significance raises ethical considerations. We consider the risk of harm to a woman or her fetus following the detection of a copy number variant of uncertain significance, whether it is ethically justifiable to withhold any test result information from a woman, what constitutes an 'informed choice' when women are offered CMA in pregnancy and whether clinicians are morally responsible for 'unnecessary' termination of pregnancy. Although we are cognisant of the distress associated with uncertain prenatal results, we argue in favour of the autonomy of women and their right to information from genome-wide CMA in order to make informed choices about their pregnancies. We propose that information material to a woman's decision-making process, including uncertain information, should not be withheld, and that it would be paternalistic for clinicians to try to take responsibility for women's decisions to terminate pregnancies. Non-directive pre-test and post-test genetic counselling is central to the delivery of these ethical objectives.     

染色体核型分析联合染色体微阵列分析在平衡易位/倒位携带者产前诊断中的应用价值

目的:探讨染色体核型分析与染色体微阵列分析（chromosomal microarray analysis,CMA）技术在染色体平衡易位/倒位携带者产前诊断中的应用价值。方法:本研究为回顾性研究。纳入既往因自然流产（≥2次）、死胎、胎儿多发畸形或染色体异常患儿生育史,夫妇双方行外周血染色体核型分析和荧光原位杂交检测确诊...     

Preimplantation genetic diagnosis of chromosome abnormalities: implications from the outcome for couples with chromosomal rearrangements

OBJECTIVES: Chromosomal rearrangements can lead to infertility or repeated spontaneous or induced abortions. The use of preimplantation genetic diagnosis (PGD) allows the selected transfer of chromosomally balanced embryos. The aim of this study was to carry out detailed analysis of the outcome of 11 PGD cycles for 8 patients carrying various chromosomal rearrangements. METHODS: Patients underwent routine in vitro fertilisation with biopsy of embryos on day 3. Specific fluorescent in situ hybridisation protocols were developed for each couple. Embryo transfer was possible in all 11 cycles. RESULTS: The outcome was four pregnancies, leading to three live births and one biochemical pregnancy. Post-zygotic mosaicism was detected in 75% of untransferred embryos, the majority of which were chaotic. Detailed follow-up and analysis provided evidence for the co-existence of chromosomally balanced and abnormal cells in six embryos. The mechanisms involved included chromosome breakage and loss of material. CONCLUSIONS: Biopsy and analysis of two blastomeres, where possible, reduced the risk of misdiagnosis in cases of balanced/aneuploid mosaics. The three live births achieved for the eight couples treated in this series, despite the poor history in almost all cases, is further proof that a policy of biopsying two cells from embryos consisting of six or more cells and a single cell from four- or five-cell embryos is compatible with a positive outcome.     

Chromosome studies in couples with repeated abortions

In a nonselected group of 26 women with 3 or more abortions and in 17 of the respective husbands, chromosomes from lymphocyte cultures were investigated. 6 persons were found to have abnormal chromosomes; in 3 women variations in the length of autosomes were found (46,XX,Gp+; 46,XX ,Gp-; 46,XX,Cq+). 1 woman showed a trisomy C mosaicism in 4% of the analyzed cells. A second one had in 4% of the mitoses a translocation mosaic with a B/D-translocation(46,XX/46,XX,t(Bq+; Dq-)). Another woman with normal karyotype showed in 3 different analyses an increased rate of secondary chromosome aberrations with a high percentage of exchanges.     

Multicolour spectral karyotyping for complex chromosomal rearrangements in repeated abortion or congenital anomalies.

Advances in molecular cytogenetics, especially the technique of fluorescence in situ hybridization (FISH), have allowed more precise definition of chromosomal structures, which are difficult to identify using conventional G-banding. Recently, a novel approach based on hybridization of 24 fluorescent-labelled chromosome painting probes was developed, termed spectral karyotyping (SKY), which allows the simultaneous and differential colour display of all human chromosomes. We have used SKY to identify not only five parental complex translocation carriers but also minute chromosome rearrangements in the fetus. Here, we concentrate attention on the clinical application of SKY for prenatal diagnosis.     

染色体平衡易位携带者妊娠风险及妊娠结局的研究

目的 探讨染色体平衡易位携带者的妊娠风险及其妊娠结局.方法 194例染色体平衡易位携带者,根据平衡易位种类分成相互易位（135例）、非同源罗伯逊易位（52例）、同源罗伯逊易位（7例）3组.调查携带者生育史并随访诊断平衡易位后的妊娠情况,比较各组自然流产、先天缺陷及正常（或）平衡易位后代概率.结果 （1）194对夫妇共妊娠503例次,其中自然流产411例次（81.7%,411/503）;产前诊断胎儿异常而终止妊娠16例次（3.2%,16/503）;活产缺陷儿36例次（7.2%,36/503）;正常（或）平衡易位后代40例次（8.0%,40/503）.（2）相互易位、非同源罗伯逊易位、同源罗伯逊易位3组,活产缺陷儿比率分别为5.7%（20/350）、10.9%（14/128）、8.0%（2/25）,3组间相互比较,差异有统计学意义（P＜0.05）;3组正常（或）平衡易位后代比率分别为6.6%（23/350）、13.3%（17/128）、0,3组间相互比较,差异有统计学意义（P＜0.05）;而3组自然流产及产前诊断胎儿异常终止妊娠比率比较,差异无统计学意义（P＞0.05）.（3）52例次先天缺陷中活产36例次（69%）,经产前诊断确诊后引产16例次（31%）.27例次先天缺陷获得细胞遗传学诊断,唐氏综合征发生率为59%（16/27）.（4）相互易位组和非同源罗伯逊易位组共有39对夫妇得到40个正常（或）平衡易位后代,同源罗伯逊易位组无正常（或）平衡易位后代.40个正常（或）平衡易位后代中26个获得产前细胞遗传学诊断,正常核型6个（23%）,平衡易位核型20个（77%）.结论 染色体平衡易位携带者自然妊娠风险大,尤其同源罗伯逊易位携带者难以获得染色体正常（或）平衡易位的后代.     

Karyotypes of 1142 couples with recurrent abortion

Cytogenetic analysis was performed on 1142 couples with recurrent pregnancy loss. The frequency of major chromosomal abnormalities per couple was 4.8%. Among 771 couples who had only abortions, the rate of rearrangement did not correlate with the number of abortions. The highest incidence of cytogenetic abnormalities (6.6%) was found in 256 couples with abortion and a normal child. With regard to pregnancy outcome, no unbalanced fetal karyotype was found in prenatal diagnoses, and 40 normal children were born. The risk of unbalanced fetal karyotype is therefore low, but probably high enough for these couples to be offered the possibility of a prenatal diagnosis.     

Future of prenatal cytogenetic studies: rapid aneuploidy testing or full karyotype

The traditional "gold standard" for prenatal diagnosis of chromosome abnormalities involves analysis of banded chromosomes obtained from cultured amniotic fluid or chorionic villus cells. Most studies are performed because of increased risk of aneuploidy of chromosomes 13, 18 and 21. It constitute 65-85% of all chromosome aberrations diagnosed prenataly. At present more rapid (in 1-3 days) methods than conventional cytogenetics, enabling the diagnosis of aneuploidy are available. They include FISH (fluorescence in situ hybridization), QF-PCR (quantitative fluorescence polymerase chain reaction) and MLPA (multiplex ligation-dependent probe amplification) techniques. However, it is important to know how many other chromosomal abnormalities would not be detected using these tests for the estimation of their clinical utility. Currently, most laboratories perform rapid tests for aneuploidy together with full karyotype. The criteria of using of rapid aneuploidy tests as a stand-alone test in prenatal diagnosis are currently discussed. Here, the diagnostic capacity and limitations of rapid tests for aneuploidy detection as well as debate on the change of the policy for cytogenetic prenatal diagnosis is presented.