植入前遗传学诊断100个周期临床分析

目的 探讨染色体易位对早期胚胎发育的影响,以及植入前遗传学诊断(PGD)技术的诊断效率和可行性.方法 回顾性分析PGD中23个罗伯逊(罗氏)易位周期、19个平衡易位周期(染色体易位组),以及58个α地中海贫血周期(地贫组)共100个周期中的胚胎发育情况、PGD的诊断效率以及临床结局.结果 染色体易位组中有354个胚胎进行PGD,321(90.7%)个胚胎有荧光原位杂交(FISH)结果,其中罗氏易位者中正常和(或)平衡易位胚胎占38.3%(64/167),显著高于平衡易位者的20.8%(32/154).地贫组有537个胚胎进行PGD,单个卵裂球的扩增效率为82.5%(443/537),诊断出正常纯合子140个、杂合子112个、异常纯合子155个、另36个诊断结果不明确,总体诊断效率为75.8%(407/537).染色体易位组中,取卵后第3天卵裂球数≥7的胚胎中,正常和(或)平衡易位发生率(34.4%,77/224)显著高于卵裂球数＜7的胚胎(19.6%,19/97),在取卵后第4天,正常和(或)平衡易位胚胎的细胞融合率为59.4%(57/96),显著高于染色体不平衡胚胎的34.2%(77/225).染色体易位组共在37个周期移植了75个胚胎,获得10例临床妊娠,临床妊娠率27.0%(10/37).地贫组共在58个周期移植了170个胚胎,获得25例临床妊娠,临床妊娠率为43.1%(25/58).结论 PGD技术可有效为染色体易位和地中海贫血基因携带者提供优生选择.染色体易位可能对着床前胚胎的发育有一定的影响.

Abstract：

Objective To investigate influence of chromosomal translocations on early embryo development and to evaluate the efficacy and feasibility of preimplantation genetic diagnosis (PGD)techniques through clinical analysis on PGD cycles. Methods Embryo development, efficacy of PGD and clinical outcome of 100 cycles were studied retrospectively, including 23 cycles with Robertsonian translocations, 19 cycles with reciprocal translocations, and 58 cycles for α-Thalassaemia. Results Among 354 embryos biopsied by PGD for translocations, 321 (90. 7% ) presented fluorescence in situ hybridization (FISH) results. The rate of normal/balanced embryos in the Robertsonian translocation was 38. 3% (64/167),which was significantly higher than 20. 8% (32/154) in the reciprocal translocation group. Amplification was achieved in 443 blastomeres from 537 embryos in Thalassaemia group, which given to an amplification efficiency rate of 82. 5% ( 443/537 ). Totally, 140 normal homozygous, 112 heterozygotes and 155 affected homozygous embryos were identified, while 36 embryos had uncertain result. The successful diagnostic rate was 75.8% (407/537). After 3 days in the translocation groups, the rate of normal and/or balanced translocations in biopsed embryos with ≥7 cells was 34. 4% (77/224), which was significantly higher than 19. 6% ( 19/97 ) of biopsed embryos with ＜ 7 cells. After 4 days, the compaction rate in normal/balanced embryos was 59.4% ( 57/96 ), which was significantly higher than 34. 2% ( 77/225 ) in imbalanced embryos significantly. Seventy-five embryos transferred in 37 cycles with translocations group led to clinical pregnancy rate of 27.0% (10/37), and 170 embryos transferred in 58 cycles with Thalassaemia got a clinical pregnancy rate of 43. 1% ( 25/58 ) . Conclusions PGD can provide management efficiently for both chromosome translocations and Thalassaemia. Translocations might have slightly negative impact on embryo development before implantation.     

Multiple micromanipulations for preimplantation genetic diagnosis do not affect embryo development to the blastocyst stage

To determine the impact of multiple micromanipulation procedures for preimplantation genetic diagnosis (PGD) on embryo development, a retrospective analysis was performed of 9,925 embryos (862 PGD cycles), which were compared with 28,126 nonbiopsied embryos (2,751 consecutive intracytoplasmic sperm injection [ICSI] cycles) from the same time period. Because fertilization rates, the proportion of embryos with > or = 6 cells on day 3, and blastocyst rates were similar in the PGD and control groups, we conclude that multiple micromanipulations on oocytes and embryos can be performed safely for PGD.     

Negligible interchromosomal effect in embryos of Robertsonian translocation carriers

It has been suggested that translocations, and perhaps other chromosome rearrangements, disturb meiotic disjunction of chromosome pairs not involved in the translocation, resulting in non-disjunction in those chromosomes (interchromosomal effect) and predisposition to trisomy offspring. Other reports have suggested an increased risk of mosaicism and chaotic embryos in translocation carriers. This study was designed to determine if such interchromosomal effects are producing significantly more chromosome abnormalities than those expected from unbalanced gametes. For that purpose, two groups of PGD patients were compared, Robertsonian translocation carriers (RBT) and carriers of X-linked diseases (XLI), of similar age. Both groups were analysed by FISH with similar DNA probes. The results indicate that overall, the higher rate of chromosome abnormalities in the RBT group was solely due to unbalanced gametes and not to an interchromosomal effect or higher incidence of mosaicism. If unbalanced and normal were combined, this proportion was 53% in XLI and 59% in RBT. However, when specific RBT translocations were studied, only a slight increase in embryos with aneuploidy for chromosome 22 was found for the t(13;14) translocation carriers, while a higher rate of post-zygotic abnormalities was observed in the more rare RBT. In conclusion, the overall rate of non-translocation related abnormalities was not increased in the RBT group compared with the control group, but a slight interchromosomal effect may exist, as some Robertsonian translocations may be more prone to produce mosaic and chaotic embryos.     

Preimplantation genetic diagnosis by fluorescence in situ hybridization of reciprocal and Robertsonian translocations

ObjectiveThe presence of reciprocal and Robertsonian chromosomal rearrangement is often related to recurrent miscarriage. Using preimplantation genetic diagnosis, the abortion rate can be decreased. Cases treated at our center were reviewed.Materials and methodsA retrospective analysis for either Robertsonian or reciprocal translocations was performed on all completed cycles of preimplantation genetic diagnosis at our center since the first reported case in 2004 until the end of 2010. Day 3 embryo biopsies were carried out, and the biopsied cell was checked by fluorescent in situ hybridization using relevant informative probes. Embryos with a normal or balanced translocation karyotype were transferred on Day 4.ResultsThirty-eight preimplantation genetic diagnosis cycles involving 17 couples were completed. A total of 450 (82.6%) of the total oocytes were MII oocytes, and 158 (60.0%) of the two-pronuclei embryos were biopsied. In 41.4% of the fluorescent in situ hybridization analyses, the results were either normal or balanced. Embryos were transferred back after 21 cycles. Three babies were born from Robertsonian translocation carriers and another two from reciprocal translocation carriers. The miscarriage rate was 0%. Among the reciprocal translocation group, the live delivery rate was 8.3% per ovum pick-up cycle and 18.2% per embryo transfer cycle. Among the Robertsonian translocation group, the live delivery rate was 14.3% per ovum pick-up cycle and 20.0% per embryo transfer cycle.ConclusionThere is a trend whereby the outcome for Robertsonian translocation group carriers is better than that for reciprocal translocation group carriers. Aneuploidy screening may possibly be added in order to improve the outcome, especially for individuals with an advanced maternal age. The emergence of an array-based technology should help improve this type of analysis.     

染色体易位的植入前遗传学诊断

目的 观察染色体平衡易位和罗伯逊(罗氏)易位基因携带者夫妇进行植入前遗传学诊断(PGD)后的胚胎染色体遗传特征和胚胎着床、妊娠情况,探讨PGD在染色体易位基因携带者夫妇实现正常生育中的意义.方法 用荧光原位杂交(FISH)技术对36对夫妇的胚胎进行PGD,其中14例为染色体平衡易位(平衡易位组),22例为染色体罗氏易位(罗氏易位组),并对诊断结果和胚胎着床、妊娠情况进行分析.结果 36例患者共活检胚胎253个,成功诊断胚胎225个,成功率为88.9%(225/253),获得可供移植的正常或平衡的胚胎共58个.平衡易位组和罗氏易位组PGD后胚胎着床率分别为36%(5/14)和14%(6/44),临床妊娠率分别为4/9和26%(5/19).结论 PGD可有效诊断胚胎染色体平衡易位和罗氏易位,避免反复流产和不必要的非意愿性终止妊娠,并获得理想的胚胎着床率和临床妊娠率.     

Clinical outcome of treatment cycles using preimplantation genetic diagnosis for structural chromosomal abnormalities

OBJECTIVES: To explore oocyte recovery, embryo quality, the number of transferable embryos and pregnancy rate after preimplantation genetic diagnosis (PGD) in patients with structural chromosomal aberrations. METHODS: PGD was performed in seven couples with Robertsonian translocations (Rob), eight couples with reciprocal translocations (Rec), two couples with inversions and one couple with a deletion. A total of 43 treatment cycles were carried out. RESULTS: A total of 14.2 oocytes per cycle were retrieved. Fertilisation and cleavage rates were 63% and 58%, respectively. Of the biopsied embryos 20% were transferable. Comparison of the Rob and Rec group revealed no significant differences in number of oocytes, fertilisation or cleavage rates. The number of transferable embryos after biopsy was significantly higher in the Rob group than in the Rec group. When embryo transfer (ET) was performed the pregnancy rate did not differ between the Rob and the Rec groups. Twenty-eight embryo transfers (one or two embryos) were carried out leading to eight clinical pregnancies (29% per ET): two twins, four singletons, one miscarriage and one ectopic pregnancy. All the children are carriers of balanced chromosomal aberrations. CONCLUSION: An acceptable pregnancy rate can be achieved among couples with structural chromosomal abnormalities.     

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.     

Clinical application of next-generation sequencing in preimplantation genetic diagnosis cycles for Robertsonian and reciprocal translocations

Purpose

The purpose of this study was to apply next-generation sequencing (NGS) technology to identify chromosomally normal embryos for transfer in preimplantation genetic diagnosis (PGD) cycles for translocations.

Methods

A total of 21 translocation couples with a history of infertility and repeated miscarriage presented at our PGD clinic for 24-chromosome embryo testing using copy number variation sequencing (CNV-Seq).

Results

Testing of 98 embryo samples identified 68 aneuploid (69.4 %) and 30 (30.6 %) euploid embryos. Among the aneuploid embryos, the most common abnormalities were segmental translocation imbalances, followed by whole autosomal trisomies and monosomies, segmental imbalances of non-translocation chromosomes, and mosaicism. In all unbalanced embryos resulting from reciprocal translocations, CNV-Seq precisely identified both segmental imbalances, extending from the predicted breakpoints to the chromosome termini. From the 21 PGD cycles, eight patients had all abnormal embryos and 13 patients had at least one normal/balanced and euploid embryo available for transfer. In nine intrauterine transfer cycles, seven healthy babies have been born. In four of the seven children tested at 18 weeks gestation, the karyotypes matched with the original PGD results.

Conclusion

In clinical PGD translocation cycles, CNV-Seq displayed the hallmarks of a comprehensive diagnostic technology for high-resolution 24-chromosome testing of embryos, capable of identifying true euploid embryos for transfer.

     

Outcome of preimplantation genetic diagnosis of translocations

Objective: To review 35 cases of preimplantation genetic diagnosis (PGD) of translocations with several methods, including telomeric probes.

Design: Retrospective study.

Setting: Clinical IVF laboratory.

Patient(s): Thirty-five couples with one partner carrying a chromosomal translocation.

Intervention(s): PGD of translocation after polar-body or embryo biopsy.

Main Outcome Measure(s): Pregnancy outcome.

Result(s): Several trends were observed. First, PGD can achieve a statistically significant reduction in spontaneous abortion, from 95% to 13%. Second, the chances of achieving pregnancy are correlated with 50% or more of the embryos being chromosomally normal. Third, patients with robertsonian translocations produced fewer abnormal gametes and more pregnancies than did patients with reciprocal translocations. Fourth, a new fluorescence in situ hybridization protocol for PGD of translocations, which involves applying telomeric probes, has proved adequately reliable with a 6% average error rate.

Conclusion(s): PGD of translocations achieves a statistically significant reduction in spontaneous abortion, both for polar-body and blastomere biopsy cases. Pregnancy outcome depended on the number of normal embryos available for transfer, with patients having <50% abnormal embryos achieving the most pregnancies. Because robertsonian translocations caused fewer abnormal embryos than reciprocal translocations, they also resulted in higher rates of implantation.     

常染色体平衡易位携带者控制性促排卵周期卵巢反应性分析

目的探讨常染色体平衡易位及类型对胚胎植入前遗传学诊断(PGD)周期控制性促排卵(COS)中卵巢反应性的影响。方法回顾性分析379对染色体平衡易位夫妇行PGD的426个COS周期,其中男方正常女方为平衡易位携带者182个周期(研究组,A组),包括罗氏易位44个周期(A1组),相互易位138个周期(A2组);女方正常男方为平衡易位携带者244个周期(对照组,B组),包括罗氏易位65个周期(B1组),相互易位179个周期(B2组)。比较各组间COS中女方卵巢反应性指标。结果研究组与对照组间年龄、体质量指数(BMI)、基础内分泌(FSH、E2、LH)、窦卵泡数(AFC)、促性腺激素(Gn)用量和使用时间、第2日和第3日胚胎数、囊胚数、卵子成熟率、囊胚形成率等均无统计学差异(P0.05);A组h CG注射日E2水平、正常信号囊胚数[(5 469.8±2 365.1)ng/L,1.4±1.4]均显著低于B组[(6 033.3±2 587.5)ng/L,1.8±1.8](P0.05),A组取卵数、MII卵子数、形成囊胚数均低于B组,但是无统计学差异(P0.05);A1组h CG注射日E2水平、正常信号囊胚数[(5 573.2±2 146.1)ng/L,1.5±1.5]显著低于B1组[(6 565.0±2 961.1)ng/L,2.8±2.2](P0.05);A2组取卵数(14.6±6.6)显著低于B2组(16.5±6.7)(P0.05)。结论 (1)女方常染色体平衡易位可能影响COS中卵巢反应性;(2)女方罗氏易位形成平衡或正常胚胎几率低于男方罗氏易位者。     

Outcomes of trophectoderm biopsy on cryopreserved blastocysts: a case series

Preimplantation genetic diagnosis (PGD) is an increasingly common adjunct to IVF. The information gained from PGD may be used to reduce the incidence of chromosomally abnormal pregnancies and augment the current selection process of embryos. As such, patients may choose to utilize PGD in either fresh or cryopreserved IVF cycles. It is a common practice to cryopreserve excess embryos at the blastocyst stage. In these cases, trophectoderm biopsy is the only technique available for PGD. This articles reports this study centre’s experience with trophectoderm biopsies of cryopreserved blastocysts in 12 patients who underwent 13 cycles of PGD. The implantation rate per embryo transferred was 46% and the ongoing pregnancy rate per embryo transfer was 63%. The results from this case series demonstrate that trophectoderm biopsy on cryopreserved blastocysts to perform PGD is logistically feasible. In addition, the rate of implantation and ongoing pregnancy were maintained within a reasonable range to justify the procedure.Preimplantation genetic diagnosis (PGD) is an increasingly common adjunct to IVF and is used to evaluate the genetic makeup of the embryo prior to transfer of the embryo into the uterus. The information gained from PGD may be used to identify single-gene disorders that result in genetic disease, reduce the incidence of chromosomally abnormal pregnancies and/or augment the selection process of embryos to be transferred. In order to perform PGD, a biopsy of the embryo is the performed and cells are removed for testing. PGD may be performed in either fresh or frozen (cryopreserved) IVF cycles. Patients who have cryopreserved embryos remaining in storage from a previous fresh cycle may wish to have these embryos tested with PGD. Many embryos are frozen on day 5 of development, referred to as the blastocyst stage. At this stage of development, embryo biopsy is performed via a technique known as ‘trophectoderm biopsy’, in which 1–3 of the cells destined to become the placenta are removed from the embryo for chromosomal testing. We report our experience with trophectoderm biopsy of frozen blastocysts in 12 patients who underwent 13 cycles of PGD. The implantation rate per embryo transferred was 46% and the ongoing pregnancy rate per embryo transfer was 63%. The results from this case series demonstrate that trophectoderm biopsy on cryopreserved blastocysts to perform PGD is logistically feasible. In addition, the rate of implantation and ongoing pregnancy were maintained within a reasonable range to justify the procedure.     

Highly abnormal cleavage divisions in preimplantation embryos from translocation carriers

We have developed preimplantation genetic diagnosis (PGD) for carriers of chromosomal abnormalities using fluorescent in situ hybridisation (FISH). Here we present the detailed analysis of 64 biopsied, normally developing embryos obtained from four Robertsonian and three reciprocal translocation carriers in 11 treatment cycles of which four resulted in normal pregnancies (three simplex, one duplex). In order to investigate the degree of mosaicism and segregation mode in the embryos, the primary analysis of the biopsied cells was extended with the analysis of all cells from the non-transferred embryos. The analysis also included a second hybridisation with two additional probes, not involved in the translocation (chromosomes 1 and 9), in order to investigate the overall degree of mosaicism. Seventeen out of 64 analysed embryos were balanced for the chromosomes involved in the translocation and 14 of these were transferred. Forty-seven out of 64 embryos (73%) were mosaic regarding the chromosomes involved in the translocation and alternate segregation mode was the most common mode of segregation. Moreover, we have found a higher degree of mosaicism for the chromosomes involved in translocations as compared to control chromosomes. This difference was more pronounced for the embryos from reciprocal translocation carriers. The results, mechanisms, significance and implications of our findings are discussed.     

女性罗氏易位携带者辅助生育治疗5例临床分析

目的:探讨应用极体分析和分裂球分析法对反复流产的女性罗氏易位携带者进行着床前遗传学诊断(PGD)的临床策略。方法:采用荧光原位杂交(FISH)技术,对5例患者用全染色体涂抹探针检测第一极体和用特异位点探针检测分裂球中相应染色体的荧光信号。5例女性罗氏易位携带者的外周血淋巴细胞染色体核型分别为:45,XX,der (13;14)(q10;q10)3例,45,XX,der(14;21)(q10;q10)、45,XX,der(21;22)(q10;q10)各1例。结果:5例患者中4例获得妊娠并分娩,其中2例经分裂球分析后妊娠,出生3个婴儿:2个正常核型,1个罗氏易位携带者;1例经极体分析诊断后分娩一正常男婴;另1例极体分析未明确诊断又行分裂球分析选择胚胎移植后,出生1个罗氏易位携带者后代。结论:(1)女性罗氏易位携带者PGD应首选极体分析,争取避免携带者出生;(2)极体分析未能得到诊断的胚胎可在分裂球期再次PGD。     

Natural selection between day 3 and day 5/6 PGD embryos in couples with reciprocal or Robertsonian translocations

Purpose

For translocation carriers, preimplantation genetic diagnosis (PGD) provides the opportunity to distinguish between normal/balanced and unbalanced embryos prior to implantation and, as such, increases the likelihood of a successful ongoing pregnancy. The data presented here compares autosomal reciprocal and Robertsonian translocation segregation patterns in day 3 versus day 5/6 IVF-PGD embryos to determine if there is a difference in the chromosome segregation patterns observed at these developmental time points.

Methods

A retrospective analysis on PGD translocation carriers at Monash IVF was performed. Segregation patterns were compared between day 3 and day 5/6 embryos to ascertain whether selection against malsegregants exists.

Results

For reciprocal translocations, 1649 day 3 embryos (139 translocations) from 144 couples and 128 day 5/6 embryos (59 translocations) from 60 couples were analysed. Day 3 segregation analysis showed that 22.3% of embryos were normal/balanced (consistent with 2:2 alternate segregation) and 77.7% were unbalanced (malsegregation). Day 5/6 segregation analysis showed that 53.1% of embryos were normal/balanced and 46.9% were unbalanced. For Robertsonian translocations, 847 day 3 embryos (8 translocations) from 54 couples and 193 day 5/6 embryos (6 translocations) from 31 couples were analysed. Day 3 segregation analysis showed that 38.7% of embryos were normal/balanced (consistent with 2:1 alternate segregation) and 61.3% were unbalanced. Day 5/6 segregation analysis showed that 74.1% of embryos were normal/balanced and 25.9% were unbalanced.

Conclusions

This data demonstrates an increase in the proportion of genetically normal/balanced embryos at day 5/6 of development. This suggests a strong natural selection process between day 3 and day 5/6 in favour of normal/balanced embryos. These findings support performing PGD testing on day 5/6 of embryo development.

     

Efficacy and clinical outcome of preimplantation genetic diagnosis using FISH for couples of reciprocal and Robertsonian translocations: the Korean experience

OBJECTIVE: To evaluate the efficacy and clinical outcome of preimplantation genetic diagnosis (PGD) using fluorescence in situ hybridization (FISH) for couples with chromosomal translocations. METHODS: PGD using FISH was performed in 59 cycles of 43 couples with reciprocal translocations, and 11 cycles of 6 couples with Robertsonian translocations. The diagnostic and clinical data were reviewed in a series of 70 treatment cycles of 49 couples from January 2001 to June 2002 at Samsung Cheil Hospital, Korea. RESULTS: A total of 1408 oocytes were retrieved, and 938 (81.7%) out of 1148 matured oocytes were fertilized by intracytoplasmic sperm injection (ICSI). Single blastomere biopsy and FISH analysis were successfully carried out in 99.3% (890/896) and 94.4% (840/890), respectively. Among 193 normal or balanced embryos, 169 embryos were transferred in 64 cycles (91.4% per started cycle). Twenty clinical pregnancies including two ectopic pregnancies and three spontaneous miscarriages (28.6% per started cycle, 31.3% per transfer cycle, 40.8% per couple) were established. Of the three spontaneous miscarriages, one was karyotyped as normal, one had an unbalanced arrangement and one was tetraploid. One case of preterm twin delivery occurred and 16 healthy babies were delivered in 12 single and 2 twin pregnancies. CONCLUSION: The clinical outcome was successful in 28.6% (14/49) of the treated couples with translocations after PGD. The spontaneous abortion rate was significantly reduced from 95.8% (69/72) to 16.7% (3/18) in these couples.     

Effect of chromosomal translocations on the development of preimplantation human embryos in vitro

OBJECTIVE: To determine the reliability of a new technique for single human blastomere karyotyping during clinical cases for preimplantation genetic diagnosis of translocations. DESIGN: Controlled clinical study. SETTING: Preimplantation genetic diagnosis and IVF program. PATIENT(S): Nineteen preimplantation genetic diagnosis cases with 11 types of translocations (10 reciprocal and one Robertsonian) involving chromosomes 1, 5, 7, 8, 9, 11, 12, 13, 14, 15, 16, 18, 20, 21, and 22. INTERVENTION(S): Blastomere biopsy followed by blastomere nucleus conversion into metaphase chromosomes. Fluorescent in situ hybridization (whole chromosome painting) was used for the detection of chromosomally unbalanced preimplantation human embryos.Main Outcome Measure(s): Percentage of informative metaphase plates and effect of unbalanced translocations on preimplantation embryo development. RESULT(S): Informative metaphases were obtained for 84% of the blastomeres. Analysis of preimplantation development of the resulting embryos showed that an unbalanced chromosomal complement does not affect embryo ability to reach the blastocyst stage in vitro. CONCLUSION(S): For the translocations tested, there is no evident selection against chromosomally unbalanced embryos at the preimplantation stage of embryo development.     

Clinical pregnancy following blastomere biopsy and PGD for a reciprocal translocation carrier: analysis of meiotic outcomes and embryo quality in two IVF cycles

A couple were referred for preimplantation genetic diagnosis (PGD) following diagnosis of a reciprocal translocation in the female partner: 46,XX,t(14;22)(q11.2;q13.3). PGD was carried out using fluorescence in situ hybridization (FISH) with probes specific for the translocated and centric segments of chromosome 22. An initial cycle was unsuccessful, producing 11 embryos for biopsy, only one of which, when followed up on day 4, yielded more than 10 nuclei (median 7.5, n=10). In addition, five of the embryos showed mosaic or chaotic chromosome constitutions; some of these embryos had fragmented or multilobed abnormal nuclei, hindering interpretation of the FISH signals. The single embryo transferred did not result in a pregnancy. A second cycle, using a revised protocol, produced 10 embryos, three of which were transferred, resulting in an ongoing singleton pregnancy. All the remaining embryos yielded 12 to 23 nuclei by day 4 (median 17, n=7). Apart from some tetraploid nuclei, only one embryo showed mosaicism. The significance of the changes in protocol leading to the successful outcome is discussed, and the pattern of meiotic segregation products is analysed and compared with other previous reports of reciprocal translocations.     

Successful pregnancy outcomes after preimplantation genetic diagnosis (PGD) for carriers of chromosome translocations

Reciprocal translocations are found in about 1 in 500 people, whereas Robertsonian translocations occur with a prevalence of 1 in 1000. Balanced carriers of these rearrangements, although phenotypically normal, may present with infertility, recurrent miscarriage, or offspring with an abnormal phenotype after segregation of the translocation at meiosis. Once the translocation has been identified, prenatal diagnosis can be offered, followed by termination of pregnancies with chromosome imbalance. Couples who have suffered repeated miscarriage or those who have undergone termination of pregnancy as a result of the translocation carrier status of one partner are looking increasingly to preimplantation genetic diagnosis (PGD) as a way of achieving a normal pregnancy. Similarly, infertile couples in which one partner is a translocation carrier may request PGD to ensure transfer of normal embryos after in vitro fertilization. Translocation PGD has been applied successfully in several centres worldwide and should now be considered as a realistic treatment option for translocation carriers who do not wish to trust to luck for a successful natural outcome.     

Successful pregnancy outcomes after preimplantation genetic diagnosis (PGD) for carriers of chromosome translocations

Reciprocal translocations are found in about 1 in 500 people, whereas Robertsonian translocations occur with a prevalence of 1 in 1000. Balanced carriers of these rearrangements, although phenotypically normal, may present with infertility, recurrent miscarriage, or offspring with an abnormal phenotype after segregation of the translocation at meiosis. Once the translocation has been identified, prenatal diagnosis can be offered, followed by termination of pregnancies with chromosome imbalance. Couples who have suffered repeated miscarriage or those who have undergone termination of pregnancy as a result of the translocation carrier status of one partner are looking increasingly to preimplantation genetic diagnosis (PGD) as a way of achieving a normal pregnancy. Similarly, infertile couples in which one partner is a translocation carrier may request PGD to ensure transfer of normal embryos after in vitro fertilization. Translocation PGD has been applied successfully in several centres worldwide and should now be considered as a realistic treatment option for translocation carriers who do not wish to trust to luck for a successful natural outcome.     

Preimplantation genetic diagnosis (PGD): the Gothenburg experience

BACKGROUND: A program for preimplantation genetic diagnosis of pre-embryos from patients with hereditary disorders was set up in our unit at Sahlgrenska University Hospital in 1994. The majority of the patients were carriers of X-chromosome linked disorders; a few patients were translocation carriers. In this paper we describe our experiences of our first 36 cycles, 30 gender determinations and six analyses of embryos with possible translocations. METHODS: Conventional hormone replacement treatment with intracytoplasmic sperm injection to fertilize the eggs followed by blastomere biopsy and fluorescent in situ hybridization at the eight cell stage was used for sexing as well as detection of translocations. RESULTS: Out of the 30 cycles in 13 patients for gender determination, blastomere biopsies could be carried out in 25 cycles. Transfer of normal female embryos (XX) was performed in 18 cycles, resulting in five pregnancies (pregnancy rate 27.8%) and an implantation rate of 20% per transfer. Three girls have been born. Hence the take home baby rate was 16.7% per transfer and 10% per started cycle. Six cycles (three patients) for detection of translocations in embryos were performed. Diagnosis was possible in four cycles. Transfer of normal embryos was carried out in one cycle. No pregnancy was achieved. CONCLUSION: Successful PGD in its clinical application demands close collaboration between a large group of specialists. Even so, the success rate is considerably lower than after conventional IVF or ICSI procedures. Taking into account the stress caused to the parents facing late interruption of pregnancy following conventional prenatal diagnosis we are convinced that this technique is well worthwhile continuing and refining.