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.     

Successful pregnancy after preimplantation genetic diagnosis in a female with Robertsonian translocation.

Preimplantation genetic diagnosis (PGD) is an alternative option for couples with chromosome abnormalities. A 34-year-old woman with balanced Robertsonian translocation [(45, XX, der(13; 14)(q10; q10)] requested PGD due to recurrent spontaneous abortion. Embryos of good quality were biopsied on day 3 post-oocyte retrieval. The aspirated blastomeres were fixed and analyzed using fluorescence in situ hybridization. In the first cycle, 2 unaffected embryos were transferred back without success. No unaffected embryo was available in the second cycle. On day 5 in the third cycle, 2 unaffected embryos were transferred resulting in a twin pregnancy. Amniocentesis confirmed the diagnosis. At the gestational age of 35 weeks, 2 healthy girls were born via cesarean section. Postnatal physical examination found no evidence of major abnormalities.     

Successful pregnancy after preimplantation genetic diagnosis for carrier of t(2;7)(p11.2;q22) with high rates of unbalanced sperm and embryos: a case report

BACKGROUND: Regarding the literature on the results of preimplantation genetic diagnosis (PGD) in reciprocal chromosomal translocation carriers seems to prevail a view that this method reduces the frequency of miscarriages, and the pregnancy rate is directly proportional to the number of normal spermatozoa. Therefore, we compared the results of sperm karyotype analysis of a carrier of familial t(2;7)(p11.2;q22) with PGD results. The carrier was ascertained as his wife had had two miscarriages. METHODS: Empirical data from a pedigree of t(2;7)(p11.2;q22) carrier was collected. A tri-color fluorescence in situ hybridization method (FISH) was used to show the meiotic segregation pattern in sperm of the proband. PGD of blastomeres from a single ICSI cycle and standard prenatal diagnosis procedures to confirm the PGD results was performed. RESULTS: Meiotic segregation pattern showed only 34.2% of normal/balanced spermatozoa. The high rate (42%) of miscarriages was observed in this family, which could be explained by chromosomal unbalanced karyotypes as a product of fertilization by unbalanced spermatozoa found with a frequency of approximately 66%. The lack of unbalanced progeny at birth suggests a natural selection of unbalanced fetuses. The 37.5% of normal/balanced embryos received after a single ICSI cycle and PGD was similar to the percentage of normal/balanced spermatozoa (34.2%). After 38 weeks a healthy girl with normal karyotype was born. CONCLUSION: The presented study is an optimistic message for translocation carriers showing that even in case with more than 60% of genetically unbalanced sperm there is a reasonable chance for reproductive success.     

Preimplantation genetic diagnosis significantly improves the pregnancy outcome of translocation carriers with a history of recurrent miscarriage and unsuccessful pregnancies

Preimplantation genetic diagnosis (PGD) for translocations has been shown to significantly reduce the risk of recurrent miscarriage, but because the majority of embryos produced are unbalanced, pregnancy rate is relatively low since 20% or more cycles have no normal or balanced embryos to transfer. The purpose of this study was to evaluate whether PGD could improve pregnancy outcome in translocation carriers with a history of two or more consecutive miscarriages and no live births. PGD for translocations was offered to translocation carriers with two or more previous miscarriages (average 3.5) and no live births (0/117 pregnancies) using a combination of distal and proximal probes to the breakpoints. After PGD, only 18.3% of embryos were normal or balanced. Only 5.3% of pregnancies were lost after PGD compared with 100% before PGD (P < 0.001). The cumulative pregnancy rate was 57.6% and the cumulative ongoing pregnancy rate was 54.5% in the short period of time of 1.24 IVF cycles, or 46.3% and 43.9% respectively per cycle. In conclusion, PGD significantly reduced losses and increased the number of viable pregnancies (P < 0.001). IVF plus PGD are a faster method of conceiving a live child than natural conception, at least for translocation carriers with recurrent miscarriages and no previous live births.     

A normal birth following preimplantation genetic diagnosis by FISH determination in the carriers of der(15)t(Y;15)(Yq12;15p11) translocations: two case reports

Purpose To investigate the clinical application of fluorescence in situ hybridization (FISH) for assessing chromosome disorders of embryos in preimplantation diagnosis of carriers with der(15)t(Y;15)(q12;p11) translocations. Methods Multicolor FISH was performed using directly-labelled DNA probes, chromosome X with one (DXZ1, Xp11.1-q11.1), but Y with two (DYZ3, Yp11.1-q11.1 and DYZ1, Yq12). Normal embryos were transferred on day 6 at blastocyst stage. Results Couple A: Three of 6 biopsied embryos were normal. Two normal blastocysts were transferred, but no pregnancy was achieved. Couple B: Three of 6 biopsied embryos were normal. Two normal blastocysts were transferred. A normal male infant weighing 3,230 g was born by cesarean section on the 39th week of gestation. All of the remaining nonreplaced embryos showed mosaic or der(15). Conclusion Embryos from carries of der(15)t(Y;15)(q12;p11) translocation showed a high frequency of chromosome abnormalities. PGD is a valuable screen tool for those couples to treat their infertility and break the transmission of der(15) chromosome for their offspring.     

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.     

Current features of preimplantation genetic diagnosis

More than 4000 preimplantation genetic diagnosis (PGD) cycles have been performed, suggesting that PGD may no longer be considered a research activity. The important present feature of PGD is its expansion to a variety of conditions, which have never been considered as an indication for prenatal diagnosis, including the late-onset disorders with genetic predisposition and preimplantation non-disease testing, with the further improvement of the accuracy of PGD for single gene disorders. PGD has also become a useful tool for the improvement of the effectiveness of IVF, through avoiding the transfer of chromosomally abnormal embryos, representing more than half of the embryos routinely transferred in IVF patients of advanced maternal age and other poor prognosis patients. PGD is of particular hope for the carriers of balanced chromosomal translocations, as it allows accurate pre-selection of a few balanced or normal embryos resulting from the extremely poor meiotic outcome, especially in reciprocal translocations. With the current progress in polymerase chain reaction- (PCR-) based detection of chromosomal abnormalities in oocytes and embryos, PGD may soon be performed for both chromosomal and single gene disorders using the same biopsied polar body or blastomere, frequently required with the currently expanded PGD application. The available clinical outcome data of more than 3000 PGD embryo transfers further suggest an acceptable pregnancy rate and safety of the procedure, as demonstrated by the follow-up information available for more than 500 children born from these PGD transfers.     

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。     

拷贝数变异测序在染色体易位夫妇植入前遗传学诊断中的临床应用

目的探讨拷贝数变异测序(copy number variation sequencing, CNV-seq)用于染色体易位夫妇胚胎植入前诊断的应用价值。 方法回顾性分析2017年1月至2018年12月,在广东省妇幼保健院生殖健康与不孕症科进行植入前遗传学诊断(preimplantation genetic diagnosis,PGD)的211对染色体易位夫妇患者的临床病例。使用CNV-seq对胚胎染色体进行检测,并对患者一般信息和PGD结果进行分析。 结果1210个胚胎中,被检出837个(79.2%)胚胎存在染色体异常,373个(30.8%)胚胎为整倍体。在241个PGD周期中,68个(27.6%)周期所有胚胎均存在染色体异常,178个(72.4%)周期至少含有一个整倍体胚胎。在176个移植周期中,130个(73.9%)确定临床妊娠,已出生46个健康婴儿,12例发生早期流产。 结论CNV-seq可准确地区分胚胎染色体是否存在异常,避免因胚胎含有染色体异常而被移植,是一种可靠而准确的PGD技术。     

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.     

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.     

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.     

Two different microarray technologies for preimplantation genetic diagnosis and screening,due to reciprocal translocation imbalances,demonstrate equivalent euploidy and clinical pregnancy rates

Purpose

To compare single nucleotide polymorphism (SNP) and comparative genomic hybridization (aCGH) microarray platforms to evaluate embryos for parental translocation imbalances and aneuploidy.

Methods

A retrospective review of preimplantation genetic diagnosis and screening (PGD/PGS) results of 498 embryos from 63 couples undergoing 75 in vitro fertilization cycles due to parental carriers of a reciprocal translocation.

Results

There was no significant difference between SNP and aCGH microarrays when comparing the prevalence of embryos that were euploid with no translocation imbalance, euploidy with a parental translocation imbalance or aneuploid with or without the parental chromosome imbalance. The clinical pregnancy rates were also equivalent for SNP (60 %) versus aCGH (65 %) microarrays. Of 498 diagnosed embryos, 45 % (226/498) were chromosomally normal without translocation errors or aneuploidy, 22 % (112/498) were euploid but had a parentally derived unbalanced chromosomal segregant, 8 % (42/498) harbored both a translocation imbalance and aneuploidy and 24 % (118/498) of embryos were genetically balanced for the parental reciprocal translocation but were aneuploid for other chromosomes. The overall clinical pregnancy rate per IVF cycle following SNP or aCGH microarray analysis was 61 % and was higher if the biopsy was done on blastocysts (65 %) versus cleavage stage embryos (59 %), although not statistically significant.

Conclusions

SNP or aCGH microarray technologies demonstrate equivalent clinical findings that maximize the pregnancy potential in patients with known parental reciprocal chromosomal translocations.     

胚胎染色体非整倍体筛查用于平衡易位携带者植入前的遗传学诊断

目的 交信号和1个Y染色体杂交信号者,则诊断为整倍体胚胎;异常杂交信号的胚胎则诊断为非整倍体胚胎.结果 (1)11个平衡易位的PGD周期中,选出杂交信号完整的130个细胞核进行分析,FISH共分析了937个荧光杂交信号,其中整倍体细胞核38个,共有304个杂交信号;其余92个为非整倍体细胞核.(2)在92个非整倍体细胞核中,Ⅰ、Ⅱ及Ⅲ级胚胎的比例分别为20个(22%)、36个(39%)及36个(39%);38个整倍体细胞核中,Ⅰ、Ⅱ及Ⅲ级胚胎的比例分别为13个(34%)、17个(45%)及8个(21%),两者的Ⅰ、Ⅱ及Ⅲ级胚胎数分别比较,差异均无统计学意义(P＞0.05).虽然染色体整倍体率在不同级别胚胎中的分布比较,差异均无统计学意义(P＞0.05),但优质胚胎(Ⅰ级+Ⅱ级)中非整倍体率仍为60%(56/92).(3)平衡胚胎来源的卵裂球细胞核整倍体率(71.4%,30/42)明显高于非平衡胚胎来源的卵裂球细胞核整倍体率(9.1%,8/88),两者比较,差异有统计学意义(P＜0.05).平衡胚胎来源的卵裂球细胞核非整倍体率(包括三体、单体、复杂非整倍体、单倍体、多倍体)明显低于非平衡胚胎来源的卵裂球细胞核非整倍体率(P＜0.05).结论 平衡易位携带者的胚胎中有较高的非整倍体率,因此,胚胎非整倍体筛查在平衡易位携带者的PGD中有重要价值和临床意义.

Abstract：

Objective To determine the importance of aneuploidy screening in preimplantation genetic diagnosis for the couples of chromosome translocation carriers. Methods To perform 11 prenatal genetic disgnosis (PGD) cycles for 7 couples of chromosome translocation carriers from January 2006 to March 2009 in the Reproductive Medical Center, First Affiliated Hospital of Zhengzhou University. To re-analyze the well-fixed, non-multinuclear and non-debris nuclei using the probes of LSI 13, 18, 21,CEPX, CEPY to detect the aneuploidy rate which come from the PGD cycles of the couples of chromosome translocation carriers. The euploid embryo was defined as two fluorescence in situ hybridization (FISH)signals of LSI 13, 18, 21 respectively and two signals of CEPX, or one signal of CEPX and one signal of CEPY. The other abnormal signals were defined as aneuploid embryo. Results (1) A tolal of 130 nuclei from 11 PGD cycles got the integrated re-FISH signals. Nine hundred and thirty-seven FISH signals were analysized, including 304 signals from 38 euploid nuclei and the others from 92 aneuploid nuclei. (2) The number of the aneuploid nuclei from grade Ⅰ , Ⅱ and Ⅲ embryo was 20 (22%), 36(39%), and 36(39%). The number of the euploid nuclei from grade Ⅰ , Ⅱ and Ⅲ embryo was 13(34%), 17(45%),and 8(21%). There was no significant difference of aneupioidy rate between the embryos form different grades (P＞0.05). However, the rate of aneuploid nucleus from good quality embryos (grade Ⅰ + grade Ⅱ) was 60% (59/92). (3) The euploidy rate was 71.4% (30/42) from balanced embryos, while 9.1%(8/88)from unbalanced embryos. There was significant difference between them (x2=53.4, P＜0.05).The rate of aneuploidy from balanced embryos was lower than those from unbalanced embryos (P＜0.05).Conclusions Since higher rate of aneuploidy was detected in embryos of the couples of chromosome translocation carriers. It is advisable to recommend the FISH re-analysis for aneuploidy screening to preimplantation genetic diagnosis for the couples of chromosome translocation carriers.     

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.     

Preimplantation genetic diagnosis of numerical and structural chromosome abnormalities

The causes of the decline in implantation rates observed with increasing maternal age are still a matter for debate. Data from oocyte donation strongly suggest that in women of advanced reproductive age, the ability to become pregnant is largely unaffected while oocyte quality is compromised. The incidence of chromosomal abnormalities in embryos is considerably higher than that reported in spontaneous abortions, suggesting that a sizable percentage of chromosomally abnormal embryos are eliminated before any prenatal diagnosis. Such loss may partly account for the decline in implantation in older women. Because of the correlation between aneuploidy and reduced implantation, it has been postulated that selection of chromosomally normal embryos could reverse this trend. Preimplantation genetic diagnosis (PGD) for aneuploidy had three objectives relevant to the present paper: (i) to increase rates of implantation, (ii) to reduce risks of spontaneous abortion, and (iii) to avoid chromosomally abnormal births. Implantation rates did not increase when only five chromosomes were analysed in blastomeres. With eight chromosomes, a significant increase in implantation was achieved. PGD can significantly reduce the incidence of spontaneous abortion. In our clinic, a significant decrease in spontaneous abortions was found, from 23 to 11% after PGD. Currently in cases diagnosed at Saint Barnabas, 0.8% chromosomally abnormal conceptions have been observed after PGD versus an expected 3.2% in a control age-matched group. It seems clear that PGD reduces the possibility of trisomic conceptions under all conditions. If a couple's main interest is to improve their chances of conceiving (improve implantation), then one should consider maternal age and number of available embryos. Improvements in conception after PGD again increase after 37 years of age with eight or nine probes. Carriers of translocations are at a high risk of miscarriage or chromosomally unbalanced offspring, and a high proportion have secondary infertility. PGD of translocations has been approached through a variety of methods, here reviewed, and has resulted in a significant reduction in spontaneous abortions. However, implantation rates in translocation carriers are directly correlated with the proportion of normal gametes, and male patients with 70% or more unbalanced spermatozoa have great difficulty in achieving pregnancy with PGD.     

Karyotype determination and reproductive guidance for short stature women with a hidden Y chromosome fragment

Two unrelated couples came to the Reproductive and Genetic Hospital of Citic-Xiangya to ask for reproductive guidance. One couple had an affected son and the other couple had secondary infertility. Conventional GTG banding showed that the women in both couples had a 46,X,add(X)(p22) karyotype. Further molecular cytogenetic studies showed that both women had a 46,X,der(X)t(X;Y)(p22;q11.2) karyotype and that the affected boy had inherited the derivative X chromosome, which resulted in an Xp contiguous gene syndrome. After an assessment of reproductive risk, the first couple conceived naturally and opted for prenatal diagnosis (PND) by amniocentesis. No abnormal karyotypes were found for the twin pregnancy and healthy twin girls were born after a full-term normal pregnancy. The second couple chose to undergo IVF with preimplantation genetic diagnosis (PGD). Two PGD cycles were performed by fluorescence in-situ hybridization. In the first PGD cycle, all three embryos had abnormal hybridization signals. In the second cycle, a male embryo with normal hybridization signals was transferred into the womb and a normal pregnancy was achieved. The results show the importance of detecting the derivative chromosome followed by PND or PGD if a woman carries an Xp;Yq translocation.Two unrelated couples came to our clinic to ask for reproductive guidance. The first couple had an affected son. Conventional GTG banding showed the woman carried a derivative metacentric X chromosome. Further molecular cytogenetic study identified this derivative X chromosome originated from a cryptic translocation between Xp and Yq and the karyotype of the woman was determined as 46,X,der(X)t(X;Y)(p22;q11.2), and the affected boy had inherited the derivative X chromosome, which resulted in an Xp contiguous gene syndrome. After assessment of reproductive risk, the couple conceived naturally. Prenatal diagnosis by amniocentesis showed a normal karyotype for the twin pregnancy and healthy twin girls were born at full term. The other couple was affected by secondary infertility. They chose to undergo IVF with preimplantation genetic diagnosis (PGD). Two PGD cycles was performed by fluorescence in-situ hybridization. In the second cycle, a male embryo with normal hybridization signals was transferred to the womb and a normal pregnancy was achieved. We emphasize the importance of identifying the hidden Y chromosome fragment to avoid the delivery of unbalanced offspring among women with a normal phenotype apart from short stature. This is the first report of the application of PGD for this unbalanced translocation 46,X,der(X)t(X;Y)(p22;q11.2).     

Complex chromosomal rearrangement—a lesson learned from PGS

Purpose

The aim of the study is to report a case of non-diagnosed complex chromosomal rearrangement (CCR) identified by preimplantation genetic screening (PGS) followed by preimplantation genetic diagnosis (PGD) which resulted in a pregnancy and delivery of healthy offspring.

Methods

A 29-year-old woman and her spouse, both diagnosed previously with normal karyotypes, approached our IVF-PGD center following eight early spontaneous miscarriages. PGS using chromosomal microarray analysis (CMA) was performed on biopsied trophectoderm. Fluorescence in situ hybridization (FISH), as well as re-karyotype, were performed on metaphase derived from peripheral blood of the couple. Subsequently, in the following PGD cycle, a total of seven blastocysts underwent CMA.

Results

A gain or loss at three chromosomes (3, 7, 9) was identified in six out of seven embryos in the first PGS-CMA cycle. FISH analysis of parental peripheral blood samples demonstrated that the male is a carrier of a CCR involving those chromosomes; this was in spite of a former diagnosis of normal karyotypes for both parents. Re-karyotype verified the complex translocation of 46,XY,t (3;7;9)(q23;q22;q22). Subsequently, in the following cycle, a total of seven blastocysts underwent PGD-CMA for the identified complex translocation. Two embryos were diagnosed with balanced chromosomal constitution. A single balanced embryo was transferred and pregnancy was achieved, resulting in the birth of a healthy female baby.

Conclusions

PGS employing CMA is an efficient method to detect unrevealed chromosomal abnormalities, including complicated cases of CCR. The combined application of array CGH and FISH technologies enables the identification of an increased number of CCR carriers for which PGD is particularly beneficial.

     

Cytogenetics of aborters and abortuses

783 aborters and 430 abortuses were studied in a prospective cytogenetic survey which attempted to link chromosome abnormalities and history of recurrent abortion. 425 female and 358 male spontaneous aborters and their 430 abortuses (310 were karotyped) showed 4 women and 2 men as balanced translocation carriers (3 Robertsonian and 3 reciprocal translocations) and a woman with an XXX karotype. 5 of the abortuses were successfully karotyped; 4 had inherited unbalanced translocation products, and the other had a balanced 13q14q translocation plus trisomy 18. Apparently, translocation chromosomes carried by aborters were transmitted to their abortuses. Structural chromosome abnormalities were found with higher frequency (.8%) among aborters than among the general adult population (.3%). Translocation carriers were more frequent among the aborters with histories of recurrent abortions (2.7%) as well as among aborters with a history of perinatal deaths (3.6%) than among those persons with no such histories (.6%). Data on 18 couples whose 2 or 3 successive spontaneous abortuses were karotyped are presented.