Preferential selection and transfer of euploid noncarrier embryos in preimplantation genetic diagnosis cycles for reciprocal translocations

Identification of cryptic balanced translocations in couples with unexplained recurrent pregnancy loss based upon embryonic PGT-A results

PURPOSE

The goal of this study is to determine whether any balanced translocation (BT) had been missed by previous karyotyping in patients with unexplained recurrent pregnancy loss (uRPL).

METHODS

This case series included 48 uRPL-affected couples with normal karyotypes. The embryos from these couples have all undergone preimplantation testing for aneuploidies (PGT-A). Based on the PGT-A's results, 48 couples could be categorized into two groups: 17 couples whose multiple embryos were detected with similar structural variations (SVs, segmental/complete) and 31 couples without such findings but who did not develop any euploid embryo despite at least three high-quality blastocysts being tested. The peripheral blood sample of each partner was then collected for mate-pair sequencing (MPseq) to determine whether any of them were BT carriers.

RESULTS

MPseq analyses identified 13 BTs in the 17 couples whose multiple embryos had similar SVs detected (13/17, 76.47%) and three BTs in the 31 couples without euploid embryo obtained (3/31, 9.7%). Among the 16 MPseq-identified BTs, six were missed due to the limited resolution of G-banding karyotyping analysis, and the rest were mostly owing to the similar banding patterns and/or comparable sizes shared by the two segments exchanged.

CONCLUSION

A normal karyotype does not eliminate the possibility of carrying BT for couples with uRPL. The use of PGT-A allows us to perceive the "carrier couples" missed by karyotyping analysis, providing an increased risk of finding cryptic BTs if similar SVs are always detected on two chromosomes among multiple embryos. Nonetheless, certain carriers with translocated segments of sub-resolution may still go unnoticed.

Nanopore sequencing for detecting reciprocal translocation carrier status in preimplantation genetic testing

BACKGROUND

Balanced reciprocal translocation (BRT) is one of the most common chromosomal abnormalities that causes infertility, recurrent miscarriage, and birth defects. Preimplantation genetic testing (PGT) is widely used to select euploid embryos for BRT carriers to increase the chance of a healthy live birth. Several strategies can be used to distinguish reciprocal translocation carrier embryos from those with a normal karyotype; however, these techniques are time-consuming and difficult to implement in clinical laboratories. In this study, nanopore sequencing was performed in two reciprocal translocation carriers, and the results were validated using the next-generation sequencing-based method named, "Mapping Allele with Resolved Carrier Status" (MaReCs).

RESULTS

The translocation breakpoints in both reciprocal translocation carriers were accurately identified by nanopore sequencing and were in accordance with the results obtained using MaReCs. More than one euploid non-balanced translocation carrier embryo was identified in both patients. Amniocentesis results revealed normal karyotypes, consistent with the findings by MaReCs and nanopore sequencing.

CONCLUSION

Our results suggest that nanopore sequencing is a powerful strategy for accurately distinguishing non-translocation embryos from translocation carrier embryos and precisely localizing translocation breakpoints, which is essential for PGT and aids in reducing the propagation of reciprocal translocation in the population.

Risk Factors Affecting Alternate Segregation in Blastocysts From Preimplantation Genetic Testing Cycles of Autosomal Reciprocal Translocations

Reciprocal translocations are the most common structural chromosome rearrangements and may be associated with reproductive problems. Therefore, the objective of this study was to analyze factors that can influence meiotic segregation patterns in blastocysts for reciprocal translocation carriers. Segregation patterns of quadrivalents in 10,846 blastocysts from 2,871 preimplantation genetic testing cycles of reciprocal translocation carriers were analyzed. The percentage of normal/balanced blastocysts was 34.3%, and 2:2 segregation was observed in 90.0% of the blastocysts. Increased TAR1 (ratio of translocated segment 1 over the chromosome arm) emerged as an independent protective factor associated with an increase in alternate segregation (p = 0.004). Female sex and involvement of an acrocentric chromosome (Acr-ch) were independent risk factors that reduced alternate segregation proportions (p < 0.001). Notably, a higher TAR1 reduced the proportion of adjacent-1 segregation (p < 0.001); a longer translocated segment and female sex increased the risk of adjacent-2 segregation (p = 0.009 and p < 0.001, respectively). Female sex and involvement of an Acr-ch enhanced the ratio of 3:1 segregation (p < 0.001 and p = 0.012, respectively). In conclusion, autosomal reciprocal translocation carriers have reduced proportions of alternate segregation in blastocysts upon the involvement of an Acr-ch, female sex, and lower TAR1. These results may facilitate more appropriate genetic counseling for couples with autosomal reciprocal translocation regarding their chances of producing normal/balanced blastocysts.

Identifying Balanced Chromosomal Translocations in Human Embryos by Oxford Nanopore Sequencing and Breakpoints Region Analysis

Background: Balanced chromosomal aberrations, especially balanced translocations, can cause infertility, recurrent miscarriage or having chromosomally defective offspring. Preimplantation genetic testing for structural rearrangement (PGT-SR) has been widely implemented to improve the clinical outcomes by selecting euploid embryos for transfer, whereas embryos with balanced translocation karyotype were difficult to be distinguished by routine genetic techniques from those with a normal karyotype.

Method: In this present study, we developed a clinically applicable method for reciprocal translocation carriers to reduce the risk of pregnancy loss. In the preclinical phase, we identified reciprocal translocation breakpoints in blood of translocation carriers by long-read Oxford Nanopore sequencing, followed by junction-spanning polymerase chain reaction (PCR) and Sanger sequencing. In the clinical phase of embryo diagnosis, aneuploidies and unbalanced translocations were screened by comprehensive chromosomal screening (CCS) with single nucleotide polymorphism (SNP) microarray, carrier embryos were diagnosed by junction-spanning PCR and family haplotype linkage analysis of the breakpoints region. Amniocentesis and cytogenetic analysis of fetuses in the second trimester were performed after embryo transfer to conform the results diagnosed by the presented method.

Results: All the accurate reciprocal translocation breakpoints were effectively identified by Nanopore sequencing and confirmed by Sanger sequencing. Twelve embryos were biopsied and detected, the results of junction-spanning PCR and haplotype linkage analysis were consistent. In total, 12 biopsied blastocysts diagnosed to be euploid, in which 6 were aneuploid or unbalanced, three blastocysts were identified to be balanced translocation carriers and three to be normal karyotypes. Two euploid embryos were subsequently transferred back to patients and late prenatal karyotype analysis of amniotic fluid cells was performed. The outcomes diagnosed by the current approach were totally consistent with the fetal karyotypes.

Conclusions: In summary, these investigations in our study illustrated that chromosomal reciprocal translocations in embryos can be accurately diagnosed. Long-read Nanopore sequencing and breakpoint analysis contributes to precisely evaluate the genetic risk of disrupted genes, and provides a way of selecting embryos with normal karyotype, especially for couples those without a reference.

A comprehensive and universal approach for embryo testing in patients with different genetic disorders

BACKGROUND

In vitro fertilization (IVF) with preimplantation genetic testing (PGT) has markedly improved clinical pregnancy outcomes for carriers of gene mutations or chromosomal structural rearrangements by the selection of embryos free of disease-causing genes and chromosome abnormalities. However, for detecting whole or segmental chromosome aneuploidies, gene variants or balanced chromosome rearrangements in the same embryo require separate procedures, and none of the existing detection platforms is universal for all patients with different genetic disorders.

METHODS

Here, we report a cost-effective, family-based haplotype phasing approach that can simultaneously evaluate multiple genetic variants, including monogenic disorders, aneuploidy, and balanced chromosome rearrangements in the same embryo with a single test. A total of 12 monogenic diseases carrier couples and either of them carried chromosomal rearrangements were enrolled simultaneously in this present study. Genome-wide genotyping was performed with single-nucleotide polymorphism (SNP)-array, and aneuploidies were analyzed through SNP allele frequency and Log R ratio. Parental haplotypes were phased by an available genotype from a close relative, and the embryonic genome-wide haplotypes were determined through family haplotype linkage analysis (FHLA). Disease-causing genes and chromosomal rearrangements were detected by haplotypes located within the 2 Mb region covering the targeted genes or breakpoint regions.

RESULTS

Twelve blastocysts were thawed, and then transferred into the uterus of female patients. Nine pregnancies had reached the second trimester and five healthy babies have been born. Fetus validation results, performed with the amniotic fluid or umbilical cord blood samples, were consistent with those at the blastocyst stage diagnosed by PGT.

CONCLUSIONS

We demonstrate that SNP-based FHLA enables the accurate genetic detection of a wide spectrum of monogenic diseases and chromosome abnormalities in embryos, preventing the transfer of parental genetic abnormalities to the fetus. This method can be implemented as a universal platform for embryo testing in patients with different genetic disorders.

Variant haplophasing by long-read sequencing: a new approach to preimplantation genetic testing workups

OBJECTIVE

To apply long-read, third-generation sequencing as a part of a general workup strategy for performing structural rearrangement (PGT-SR) and monogenic disease (PGT-M) embryo testing.

DESIGN

Prospective study.

SETTING

In vitro fertilization unit.

PATIENT(S)

Couples presenting for PGT-SR (n = 15) and PGT-M (n = 2).

INTERVENTION(S)

Blastocyst biopsy with molecular testing for translocation breakpoints or mutations (targets).

MAIN OUTCOME MEASURE(S)

Detailed, parental-phased, single-nucleotide polymorphism (SNP) profiles around targets for selection of informative polymorphic markers to simplify and facilitate clinical preimplantation genetic testing (PGT) designs that enable discrimination between carrier and noncarrier embryos.

RESULT(S)

High definition of chromosome breakpoints together with closely phased polymorphic markers was achieved for all 15 couples presenting for PGT-SR. Similarly, for the two couples presenting for PGT-M, tightly linked informative markers around the mutations were also simply identified. Three couples with translocations t(1;17)(q21;p13), t(3;13)(p25;q21.2), and t(12;13)(q23;q22) proceeded with PGT-SR, requesting preferential identification of noncarrier embryos for transfer. Following selection of a set of informative SNPs linked to breakpoints, we successfully performed PGT-SR tests, resulting in ongoing pregnancies with a noncarrier fetus for all couples. Similarly, with the use of tests based on informative SNPs linked to the parental mutations, one couple proceeded with PGT-M for maple syrup urine disease, resulting in an ongoing pregnancy with a disease-free fetus.

CONCLUSION(S)

For couples contemplating clinical PGT, variant haplophasing around the target reduces the workup process by enabling rapid selection of closely linked informative markers for patient-specific test design.

Successful birth after preimplantation genetic testing for a couple with two different reciprocal translocations and review of the literature

BACKGROUND

Preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) is widely applied in couples with single reciprocal translocation to increase the chance for a healthy live birth. However, limited knowledge is known on the data of PGT-SR when both parents have a reciprocal translocation. Here, we for the first time present a rare instance of PGT-SR for a non-consanguineous couple in which both parents carried an independent balanced reciprocal translocation and show how relevant genetic counseling data can be generated.

METHODS

The precise translocation breakpoints were identified by whole genome low-coverage sequencing (WGLCS) and Sanger sequencing. Next-generation sequencing (NGS) combining with breakpoint-specific polymerase chain reaction (PCR) was used to define 24-chromosome and the carrier status of the euploid embryos.

RESULTS

Surprisingly, 2 out of 3 day-5 blastocysts were found to be balanced for maternal reciprocal translocation while being normal for paternal translocation and thus transferable. The transferable embryo rate was significantly higher than that which would be expected theoretically. Transfer of one balanced embryo resulted in the birth of a healthy boy.

CONCLUSION(S)

Our data of PGT-SR together with a systematic review of the literature should help in providing couples carrying two different reciprocal translocations undergoing PGT-SR with more appropriate genetic counseling.

Feasibility study of using unbalanced embryos as a reference to distinguish euploid carrier from noncarrier embryos by single nucleotide polymorphism array for reciprocal translocations

OBJECTIVES

To study the feasibility of using unbalanced embryos as a reference in distinguishing euploid carrier and noncarrier embryos by single nucleotide polymorphism (SNP) array-based preimplantation genetic testing (PGT) for reciprocal translocations.

METHODS

After comprehensive chromosome screening (CCS), euploid embryos were identified as normal or carriers using a family member as a reference. Next, unbalanced embryos were used as a reference, and the results were compared with the previous ones. Karyotypes of transferred embryos were validated by prenatal diagnosis.

RESULTS

Of 995 embryos from 110 couples, 288 were found to be euploid. Using a family member as a reference, 142 and 144 embryos were tested to be euploid noncarrier and carrier respectively, and the remaining 2 embryos were undetermined. When unbalanced embryos were selected as references, all the results were consistent with the previous ones. A total of 107 embryos were transferred, resulting in 66 clinical pregnancies. Karyotypes of prenatal diagnosis were all in accordance with the results of tested embryos.

CONCLUSIONS

SNP array-based haplotyping is a rapid and effective way to distinguish between euploid carrier and noncarrier embryos. In case no family member is available as a reference, unbalanced embryos can be used for identification of euploid carrier and noncarrier embryos.

Third-generation sequencing: any future opportunities for PGT?

PURPOSE

To investigate use of the third-generation sequencing (TGS) Oxford Nanopore system as a new approach for preimplantation genetic testing (PGT).

METHODS

Embryos with known structural variations underwent multiple displacement amplification to create fragments of DNA (average ~ 5 kb) suitable for sequencing on a nanopore.

RESULTS

High-depth sequencing identified the deletion interval for the relatively large HBA1/2--SEA alpha thalassemia deletion. In addition, STRs were able to be identified in the primary sequence data for potential use in conventional PGT-M linkage confirmation. Sequencing of amplified embryo DNA carrying a translocation enabled balanced embryos to be identified and gave the precise identification of translocation breakpoints, offering the opportunity to differentiate carriers from non-carrier embryos. Low-pass sequencing gave reproducible profiles suitable for simple identification of whole-chromosome and segmental aneuploidies.

CONCLUSION

TGS on the Oxford Nanopore is a possible alternative and versatile approach to PGT with potential for performing economical workups where the long read sequencing information can be used for assisting in a traditional PGT workup to design an accurate and reliable test. Additionally, application of TGS has the possibility of providing combined PGT-A/SR or in selected stand-alone PGT-M cases involving pathogenic deletions. Both of these applications offer the opportunity for simultaneous aneuploidy detection to select either balanced embryos for transfer or additional carrier identification. The low cost of the instrument offers new laboratories economical entry into onsite PGT.

Coenzyme Q10 supplementation of human oocyte in vitro maturation reduces postmeiotic aneuploidies

OBJECTIVE

To evaluate the effect of coenzyme Q10 (CoQ10) supplementation on oocyte maturation rates and postmeiotic aneuploidy rates during in vitro maturation (IVM) of human oocytes.

DESIGN

Clinical laboratory observation.

SETTING

Hospital and university laboratories.

PATIENT(S)

Forty-five patients aged ≥38 years and 18 patients aged ≤30 years undergoing in vitro fertilization.

INTERVENTION(S)

The germinal vesicle-stage oocytes and associated cumulus cells were cultured in IVM media for 24-48 hours with or without 50 μmol/L CoQ10. Oocyte maturation rates were determined based on the presence or absence of the first polar body. Postmeiotic aneuploidies were determined using next-generation sequencing analyses of biopsied polar bodies.

MAIN OUTCOME MEASURE(S)

Oocyte maturation rates, postmeiotic oocyte aneuploidy rates, and chromosome aneuploidy frequencies.

RESULT(S)

In women aged 38-46 years, 50 μmol/L CoQ10 significantly increased oocyte maturation rates (82.6% vs. 63.0%; P=.035), reduced oocyte aneuploidy rates (36.8% vs. 65.5%; P=.020), and reduced chromosome aneuploidy frequencies (4.1% vs. 7.0%; P=.012. In women aged ≤30 years, we failed to demonstrate an effect of CoQ10 on oocyte maturation rates or postmeiotic aneuploidies.

CONCLUSION(S)

CoQ10 supplementation during IVM increased oocyte maturation rates and reduced postmeiotic aneuploidies for older women.

Partial trisomy 4q and monosomy 5p inherited from a maternal translocationt(4;5)(q33; p15) in three adverse pregnancies

Background

Carriers of balanced reciprocal chromosomal translocations are at known reproductive risk for offspring with unbalanced genotypes and resultantly abnormal phenotypes. Once fertilization of a balanced translocation gamete with a normal gamete, the partial monosomy or partial trisomy embryo will undergo abortion, fetal arrest or fetal malformations. We reported a woman with chromosomal balanced translocation who had two adverse pregnancies. Prenatal diagnosis was made for her third pregnancy to provide genetic counseling and guide her fertility.

Case presentation

We presented a woman with chromosomal balanced translocation who had three adverse pregnancies. Routine G banding and CNV-seq were used to analyze the chromosome karyotypes and copy number variants of amniotic fluid cells and peripheral blood. The karyotype of the woman was 46,XX,t(4;5)(q33;p15). During her first pregnancy, odinopoeia was performed due to fetal edema and abdominal fluid. The umbilical cord tissue of the fetus was examined by CNV-seq. The results showed a genomic gain of 24.18 Mb at 4q32.3-q35.2 and a genomic deletion of 10.84 Mb at 5p15.2-p15.33 and 2.36 Mb at 15q11.1-q11.2. During her second pregnancy, she did not receive a prenatal diagnosis because a routine prenatal ultrasound examination found no abnormalities. In 2016, she gave birth to a boy. The karyotype the of the boy was 46,XY,der(5)t(4;5)(q33;p15)mat. The results of CNV-seq showed a deletion of short arm of chromosome 5 capturing regions 5p15.2-p15.33, a copy gain of the distal region of chromosome 4 at segment 4q32.3q35.2, a duplication of chromosome 1 at segment 1q41q42.11 and a duplication of chromosome 17 at segment 17p12. During her third pregnancy, she underwent amniocentesis at 17 weeks of gestation. Chromosome karyotype hinted 46,XY,der(5)t(4;5)(q33;p15)mat. Results of CNV-seq showed a deletion of short arm (p) of chromosome 5 at the segment 5p15.2p15.33 and a duplication of the distal region of chromosome 4 at segment 4q32.3q35.2.

Conclusions

Chromosomal abnormalities in three pregnancies were inherited from the mother. Preimplantation genetic diagnosis is recommended to prevent the birth of children with chromosomal abnormalities.

Preimplantation Genetic Testing for Chromosomal Abnormalities: Aneuploidy, Mosaicism, and Structural Rearrangements

There is a high incidence of chromosomal abnormalities in early human embryos, whether they are generated by natural conception or by assisted reproductive technologies (ART). Cells with chromosomal copy number deviations or chromosome structural rearrangements can compromise the viability of embryos; much of the naturally low human fecundity as well as low success rates of ART can be ascribed to these cytogenetic defects. Chromosomal anomalies are also responsible for a large proportion of miscarriages and congenital disorders. There is therefore tremendous value in methods that identify embryos containing chromosomal abnormalities before intrauterine transfer to a patient being treated for infertility—the goal being the exclusion of affected embryos in order to improve clinical outcomes. This is the rationale behind preimplantation genetic testing for aneuploidy (PGT-A) and structural rearrangements (-SR). Contemporary methods are capable of much more than detecting whole chromosome abnormalities (e.g., monosomy/trisomy). Technical enhancements and increased resolution and sensitivity permit the identification of chromosomal mosaicism (embryos containing a mix of normal and abnormal cells), as well as the detection of sub-chromosomal abnormalities such as segmental deletions and duplications. Earlier approaches to screening for chromosomal abnormalities yielded a binary result of normal versus abnormal, but the new refinements in the system call for new categories, each with specific clinical outcomes and nuances for clinical management. This review intends to give an overview of PGT-A and -SR, emphasizing recent advances and areas of active development.

Analysis of balanced reciprocal translocations in patients with subfertility using single-molecule optical mapping

PURPOSE

Approximately 1% of individuals who carry a balanced reciprocal translocation (BRT) are subfertile. Current karyotyping does not have the resolution to determine whether the breakpoints of the involved chromosomes perturb genes important for fertility. The aim of this study was to apply single-molecule optical mapping (SMOM) to patients presenting for IVF (in vitro fertilization) to ascertain whether the BRT disrupted any genes associated with normal fertility.

METHODS

Nine subfertile patients with different BRTs were recruited for the study. Methyltransferase enzyme DLE1 was used to fluorescently label their genomic DNA samples at the recognition motif CTTAAG. The SMOM was performed on the Bionano platform, and long molecules aligned against the reference genome hg19 to identify the breakpoint regions. Mate-pair and PCR-Sanger sequencing were used to confirm the precise breakpoint sequences.

RESULTS

Both breakpoint regions in each of the nine BRTs were finely mapped to small regions of approximately 10 Kb, and their positions were consistent with original cytogenetic banding patterns determined by karyotyping. In three BRTs, breakpoints disrupted genes known to be associated with male infertility, namely NUP155 and FNDC3A [46,XY,t(5;13)(p15;q22)], DPY19L1 [46,XY,t(1;7)(p36.3;p15), and BAI3 [46,XY,t(3;6)(p21;q16)].

CONCLUSIONS

The SMOM has potential clinical application as a rapid tool to screen patients with BRTs for underlying genetic causes of infertility and other diseases.

High-resolution mapping of reciprocal translocation breakpoints using long-read sequencing

Long-read nanopore sequencing enables direct high-resolution breakpoint mapping on balanced carriers of reciprocal translocation. The mean sequencing depth on the translocated chromosomes to achieve accurate mapping of breakpoints ranged from 2.5-fold to 6.2-fold. To speed up determination of the breakpoints from long-read sequencing data, alignment reads on the translocated chromosomes were extracted before piped into NanoSV. Checking the position of breakpoints on Interactive Genomics Viewer (IGV) was crucial to successful design of breakpoint PCR primers, especially when large deletion was involved at the breakpoints.

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Long-read sequencing enables accurate breakpoint mapping with base-pair resolution

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Splitting bam files by translocated chromosomes drastically speeded up the breakpoint determination

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IGV helps to identify the breakpoint positions and facilitate the design of breakpoint PCR primers

BasePhasing: a highly efficient approach for preimplantation genetic haplotyping in clinical application of balanced translocation carriers

BACKGROUND

Preimplantation genetic testing (PGT) has already been applied in chromosomally balanced translocation carriers to improve the clinical outcome of assisted reproduction. However, traditional methods could not further distinguish embryos carrying a translocation from those with a normal karyotype prior to implantation.

METHODS

To solve this problem, we developed a method named "Chromosomal Phasing on Base level" (BasePhasing), which based on Infinium Asian Screening Array-24 v1.0 (ASA) and a specially phasing pipeline. Firstly, by comparing the number of single nucleotide polymorphism (SNP) loci in different minor allele frequencies (MAFs) and in 2Mbp continuous windows of ASA chip and karyomap-12 chip, we verified whether ASA could be adopted for genome-wide haplotype linkage analysis. Besides, the whole gene amplification (WGA) of 3-10 cells of GM16457 cell line was used to verify whether ASA chip could be used for testing of WGA products. Finally, two balanced translocation families were utilized to carry out BasePhasing and to validate the feasibility of its clinical application.

RESULTS

The average number of SNP loci in each window of ASA (473.2) was twice of that of Karyomap-12 (201.2). The coincidence rate of SNP loci in genomic DNA and WGA products was about 97%. The 5.3Mbp deletion was detected positively in cell line GM16457 of both genomic DNA and WGA products, and haplotype linkage analysis was performed in genome wide successfully. In the two balanced translocation families, 18 blastocysts were analyzed, in which 8 were unbalanced and the other 10 were balanced or normal chromosomes. Two embryos were transferred back to the patients successfully, and prenatal cytogenetic analysis of amniotic fluid was performed in the second trimester. The results predicted by BasePhasing and prenatal diagnosis were totally consistent.

CONCLUSIONS

Infinium ASA bead chip based BasePhasing pipeline shows good performance in balanced translocation carrier testing. With the characteristics of simple operation procedure and accurate results, we demonstrate that BasePhasing is one of the most suitable methods to distinguish between balanced and structurally normal chromosome embryos from translocation carriers in PGT at present.

Preimplantation genetic testing of Robertsonian translocation by SNP array-based preimplantation genetic haplotyping

OBJECTIVES

The present study attempted to confirm a method that distinguishes a balanced Robertsonian translocation carrier embryo from a truly normal embryo in parallel with comprehensive chromosome screening (CCS).

METHODS

Comprehensive chromosome screening was performed in 107 embryos from 11 couples carrying Robertsonian translocations. Among them, embryos from 2 families had been transferred before the diagnosis of translocation, which resulted in successful pregnancies; embryos from the remaining families were transferred after the identification of translocations. The single nucleotide polymorphism (SNP) genotypes were acquired on a genome-wide basis, and breakpoint regions and flanking were assessed by establishing haplotypes. The predicted karyotypes from the transferred embryos were confirmed by prenatal diagnosis.

RESULTS

Among the 9 families finally undergoing translocation diagnosis, the amniotic cell karyotypes of 3 families were concordant with the results predicted by preimplantation genetic haplotyping, revealing a good consistency rate. After CCS, the euploid embryos from 2 other families could not be further detected because of the absence of abnormal embryos as probands.

CONCLUSIONS

Molecular karyotypes and haplotypes could be established with SNP microarray simultaneously in each embryo. SNP array-based PGT can simultaneously complete the CCS and identify Robertsonian translocation carriers, thus making it possible to prevent Robertsonian translocations from being passed to subsequent generations.