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

Cumulative outcome of pre-implantation genetic diagnosis for sickle cell disease: a 5-year review

To review the cumulative outcome of pre-implantation genetic diagnosis (PGD) cycles performed for prevention of sickle cell disease (SCD). Couples referred for PGD for SCD between April 2012 and October 2017 were included. Ovarian stimulation was performed using a short gonadotrophin-releasing hormone (GnRH) antagonist protocol and follicle-stimulating hormone injections. The GnRH agonist was used to trigger oocyte maturation. Oocytes were fertilised using intracytoplasmic sperm injection. Trophectoderm biopsy was performed on day 5 or 6 followed by vitrification. Genetic testing was done using pre-implantation genetic haplotyping. A total of 60 couples started 70 fresh PGD cycles (mean 1·2 cycles/couple) and underwent a total of 74 frozen-embryo-transfer (FET) cycles (mean 1·3 FET/couple). The mean (SD) female age was 33 (4·4) years and the mean (SD) anti-müllerian hormone level was 22·9 (2·8) pmol/l. The cumulative live-birth rate was 54%/PGD cycle started and 63%/couple embarking on PGD. The rate of multiple births was 8%. The cumulative outcome of PGD treatment for prevention of SCD transmission is high and PGD treatment should be offered to all at-risk couples.

Clinical outcomes for couples containing a reciprocal chromosome translocation carrier without preimplantation genetic diagnosis

OBJECTIVE

To evaluate the pregnancy outcomes of couples containing a carrier of a reciprocal chromosome translocation (RCT) after assisted reproductive technology without preimplantation genetic diagnosis.

METHODS

A retrospective study was performed using data for couples with an RCT carrier and control couples with a normal karyotype (1:4 ratio) who underwent assisted reproductive technology cycles at a Chinese fertility center in 2010-2011. The embryos were fertilized via in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Only the first pick-up cycles were used for analysis. Clinical variables were compared.

RESULTS

Compared with the control group (n=164), the RCT group (n=41) had a marginally lower clinical pregnancy rate (46.3% [19/41] vs 54.3% [89/164]), implantation rate (21.7% [23/106] vs 26.9% [118/438]), multiple-gestation pregnancy rate (21.1% [4/19] vs 32.6% [29/89]), and delivery rate (36.6% [15/41] vs 47.6% [78/164]), whereas the spontaneous abortion rate was slightly higher (21.1% [4/19] vs 12.4% [11/89]). However, none of these differences were significant.

CONCLUSION

The clinical outcomes for RCT carriers were acceptable after IVF/ICSI without performing preimplantation genetic diagnosis, indicating that this approach might comprise a feasible alternative fertility treatment for RCT carriers.

Outcome of preimplantation genetic diagnosis using FISH analysis for recurrent miscarriage in low-risk reciprocal translocation carriers

OBJECTIVE

To assess PGD outcome using FISH analysis in couples with a history of recurrent miscarriage associated with a parental carrier of reciprocal translocation.

STUDY DESIGN

Couples in whom one partner was a carrier of a reciprocal translocation and had a history of two or more miscarriages and a low risk of a live born offspring with an unbalanced chromosomal rearrangement, underwent PGD treatment between 2000 and 2012.

RESULTS

91 couples started 171 fresh and 11 frozen PGD cycles. Of the fresh cycles, 162 (95%) reached oocyte retrieval and 107 (63%) had embryo transfer. In 14 cycles (8%), surplus embryos were cryopreserved. Pregnancy was achieved in 52 fresh PGD cycles, leading to 20 miscarriages and 32 live births. Eleven frozen embryo transfer cycles resulted in two miscarriages and three live births. The overall live birth rate was 19% per fresh and frozen PGD cycle started (35/182) and miscarriage rate was 39% per pregnancy (22/57). The cumulative live birth rate was 32% per couple (29/91).

CONCLUSION

After PGD for recurrent miscarriage in low-risk reciprocal translocation carriers, the miscarriage risk remains high and chance of live birth is low. For those translocation carriers, natural conception may be a better option.

Obstetric and neonatal outcomes in blastocyst-stage biopsy with frozen embryo transfer and cleavage-stage biopsy with fresh embryo transfer after preimplantation genetic diagnosis/screening

OBJECTIVE

To study whether embryo biopsy for preimplantation genetic diagnosis/preimplantation genetic screening (PGD/PGS) can influence pregnancy complications and neonatal outcomes.

DESIGN

Retrospective analysis.

SETTING

University-affiliated center.

PATIENT(S)

This study included data from women and their neonates born after PGD/PGS (n = 317).

MAIN OUTCOME MEASURE(S)

Questionnaires were designed to obtain information relating to pregnancy complications and neonatal outcomes.

INTERVENTION(S)

Two major strategies for PGD/PGS were evaluated. Blastocyst-stage biopsy and frozen embryo transfer (BB-FET) was carried out in 166 patients, and cleavage-stage biopsy and fresh embryo transfer (CB-ET) was carried out in 129 patients.

RESULT(S)

The incidence of gestational hypertension was significantly higher in BB-FET compared with in CB-ET (9.0% vs. 2.3%, adjusted odds ratio [OR] and 95% confidence interval [CI], 4.85 [1.34, 17.56]). In twins, the birthweight (median [range], 2.70 kg [1.55-3.60 kg] vs. 2.50 kg [1.23-3.75 kg]) was higher in BB-FET than in CB-ET and the gestational age was longer in BB-FET than in CB-ET (median [range], 36.71 weeks [31.14-39.29 weeks] vs. 35.57 weeks [30.57-38.43 weeks]). There was no difference in the incidence of singleton births between the two groups except in the incidence of preterm births (28-37 weeks; 5.3% vs. 16.5% in CB-ET and BB-FET). No significant differences were detected in the incidence of perinatal deaths, birth defects, gender of neonates, and large for gestational age in both singletons and twins, although the numbers of some events were small.

CONCLUSION(S)

BB-FET is associated with a higher incidence of gestational hypertension but better neonatal outcomes compared with CB-ET, especially in twins.

Successful PGD cycles for mosaic Robertsonian translocation carriers provide insights into the mechanism of formation of the derivative chromosomes

Preimplantation genetic diagnosis (PGD) has been carried out for two couples with different mosaic Robertsonian translocations. Two PGD cycles for a mosaic 13;13 homologous Robertsonian translocation carrier resulted in the birth of a healthy child in each cycle, illustrating the importance of scanning G-banded preparations from homologous Robertsonian carriers for the presence of a normal cell line. One couple was referred for PGD because the male partner carried a mosaic 14;15 Robertsonian translocation with a normal cell line. A single PGD cycle resulted in the birth of a healthy child. Follow-up studies and extended FISH analysis of the carrier's lymphocytes detected three cell lines, two carrying different 14;15 Robertsonian chromosomes and one normal cell line. The two 14;15 Robertsonian chromosomes had different breakpoints in the proximal short arm regions. We suggest that the presence of the D15Z1 polymorphism on the short arm of one chromosome 14 mediated the post-zygotic formation of the two different Robertsonian chromosomes.

Meiotic segregation of Robertsonian translocations ascertained in cleavage-stage embryos--implications for preimplantation genetic diagnosis

BACKGROUND

The aim of this study was to ascertain the prevalence of meiotic segregation products in embryos from carriers of 13/14 and 14/21 Robertsonian translocations and to estimate the predictive value of testing single cells using the fluorescence in situ hybridization (FISH) technique, to provide more information for decision-making about PGD.

METHODS

In this prospective cohort study, the copy number of translocation chromosomes in nuclei from lysed blastomeres of cleavage-stage embryos was ascertained using locus-specific FISH probes. Logistic regression analysis, controlling for translocation type, female age and fertility status, was used to calculate the odds ratio (OR) of unbalanced segregation products for female and male heterozygotes. The primary diagnostic measure was the predictive value of the test result. The primary outcome measure was the live birth rate per couple.

RESULTS

Female carriers were four times more likely than male carriers to produce embryos with an unbalanced translocation product (OR 3.8, 95% confidence interval 2.0-7.2, P < 0.001). The prevalence of abnormality for the chromosomes tested in embryos from female or male heterozygotes was estimated to be 43 or 28%, respectively, while estimates of the predictive value were 93-100 or 96-100% for a normal test result and 79 or 57% for an abnormal test result. The live birth rate per couple was 58% for female carriers and 50% for male carriers.

CONCLUSIONS

For female carriers, PGD using FISH could reduce the risk of miscarriage from either translocation or the risk of Down syndrome from the 14/21 Robertsonian translocation. PGD using FISH for male carriers is unlikely to be indicated given the relatively low prevalence of chromosome imbalance and low predictive value.

Preimplantation genetic diagnosis for the prevention of sickle cell disease: current trends and barriers to uptake in a London teaching hospital

INTRODUCTION

Sickle cell disease (SCD) is a clinically significant hemoglobinopathy with increasing global incidence. We describe our experience of using pre-implantation genetic diagnosis (PGD) for the prevention of SCD at a tertiary referral centre in London.

METHODS

Between January 2002 and December 2007, of 78 at-risk couples referred for PGD treatment, 12 couples (15%) underwent 16 PGD cycles for the prevention of SCD. RESULTS. The live birth rate was 13% per initiated cycle, 18% per embryo transfer and 17% per couple.

CONCLUSIONS

Although PGD for prevention of the birth of a child affected by SCD is a viable treatment option for couples at risk of having an affected child, potential barriers to uptake of this service need to be fully addressed to ensure its availability to all couples seeking to avoid having a child affected with SCD.

Single-cell DNA and FISH analysis for application to preimplantation genetic diagnosis

Preimplantation genetic testing, which includes preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS), is a form of a very early prenatal testing. The goal of this method is to avoid transfer of embryos affected with a specific genetic disease or condition. This unit describes the steps involved in amplifying DNA from a single blastomere and specific assays for detecting a variety of DNA mutations. For some assays, whole-genome amplification by primer-extension preamplification (PEP) is performed prior to analysis. Support protocols describe the biopsy of one or two blastomeres from the developing preimplantation embryo, isolation for further investigation of all blastomeres from embryos shown to have the mutant allele, and isolation of single lymphocytes or lymphoblastoid cells as models for single-cell DNA analysis. A procedure for FISH analysis on single interphase blastomeres is provided along with support protocols for probe preparation and probe validation, which is recommended as a preliminary step before performing any PGD or PGS FISH analysis.

Clinical application of preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) is an early alternative to prenatal diagnosis that is suitable for a small group of patients who are at substantial risk of conceiving a pregnancy affected by a known genetic defect. Four centres are licensed to perform PGD in the UK. This article reviews the clinical experience of PGD at the Guy's and St Thomas' Centre for Preimplantation Genetic Diagnosis, now the busiest unit for PGD in the UK, and compares it with information from other centres in Europe. The results from the first 40 cycles of treatment and the 12 pregnancies arising from those cycles are detailed. It is our belief that PGD should be seen as an extension of a clinical genetic service, rather than an arm of assisted conception. Making the distinction between treatment for infertility and prevention of genetic defect as part of genetic service provision may improve access to health service funding for patients deserving of PGD.

Can preimplantation genetic diagnosis overcome recurrent pregnancy failure?

PURPOSE OF REVIEW

Preimplantation genetic diagnosis is widely used for the detection of embryo aneuploidy before implantation, with the aim of avoiding miscarriage or pregnancy termination of an aneuploid fetus. The majority of first trimester miscarriages occur due to chromosomal imbalances. The aim of this review is to assess whether preimplantation genetic diagnosis can help women who suffer from recurrent pregnancy loss.

RECENT FINDINGS

Several in-vitro fertilization clinics have employed preimplantation genetic diagnosis in women with recurrent pregnancy loss. Patients were classified into groups according to their age. Preimplantation genetic diagnosis was very successful in treating couples where one of the parents was a carrier of a balanced chromosomal abnormality such as a translocation. Similarly, recurrent pregnancy loss rate was reduced in women more than 35 years in age with a normal karyotype. On the other hand, in younger patients the beneficial effect of this procedure is debatable. In general, women with recurrent pregnancy loss produced more abnormal embryos than control groups.

SUMMARY

Preimplantation genetic diagnosis can be beneficial for three major subgroups of patients with recurrent pregnancy loss: couples carrying chromosomal translocations; women more than 35 years of age; women of any age whose previous miscarriages were due to fetal aneuploidy. It is likely that the rate of miscarriage will be further reduced with the new advances in methods of performing preimplantation genetic diagnosis for more chromosomes.

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

Five years’ experience of preimplantation genetic diagnosis in the Parisian Center: outcome of the first 441 started cycles

OBJECTIVE

To investigate the evolution of techniques and strategies and to evaluate the results of preimplantation genetic diagnosis (PGD) from January 2000 to December 2004 in chromosomal, monogenic and mitochondrial DNA disorders treated at our institution.

DESIGN

Retrospective study.

SETTING

Single French Parisian PGD center.

PATIENT(S)

Patients at risk of transmitting a serious genetic disorder to their offspring.

INTERVENTION(S)

171 couples enrolled in the program undergoing stimulated and frozen embryo replacement cycles with PGD.

MAIN OUTCOME MEASURE(S)

Results of the 441 first PGD cycles performed for various genetic conditions.

RESULT(S)

During 5 years, 416 stimulation and 25 frozen embryo replacement cycles were started, among which 52 clinical and 47 ongoing pregnancies occurred. In stimulation cycles, the overall ongoing pregnancy rate was 24% per embryo transfer, 11% per started cycle, and 27% per couple. The implantation rate was 16%.

CONCLUSION(S)

These encouraging results demonstrate that PGD might be considered as a valid alternative to prenatal diagnosis. Nevertheless, couples referred for PGD must be selected and counseled appropriately, considering the complexity of the treatment and the relatively low take-home baby rate.

Three hundred and thirty cycles of preimplantation genetic diagnosis for serious genetic disease: clinical considerations affecting outcome

OBJECTIVE

To report on our experience with preimplantation genetic diagnosis (PGD) cycles performed for serious genetic disease in relation to the clinical factors affecting outcome.

DESIGN

Retrospective review of data from a single centre.

SETTING

Tertiary referral PGD centre in a London teaching hospital.

METHODS

The PGD cycles included 172 cycles for chromosome rearrangements, 96 cycles for single-gene disorders and 62 cycles for X-linked disorders. In vitro fertilisation was the preferred method in chromosome rearrangement and X-linked cases, while intra cytoplasmic sperm injection was used in all single-gene disorders. Appropriate in situ hybridisation fluorescence probes were used in chromosome rearrangement and X-linked cases and polymerase chain reaction was used in single-gene disorders. All pregnancies were followed till delivery.

MAIN OUTCOME MEASURE

Live birth rate per PGD cycle started.

RESULTS

Eighty-six percent of cycles started (283) reached oocyte retrieval and 3743 eggs were collected, of which 2086 fertilised normally (55.7%). Two hundred and fifty cycles (76%) had embryos sutiable for biopsy on day 3 of in vitro culture, 1714 embryos were biopsied, and in 205 cycles (62%), there was at least one unaffected embryo available for transfer, resulting in 90 pregnancies, 68 clinical pregnancies and 58 live birth. The live birth rate was 18% per cycle started, 21% per egg retrieval and 28% per embryo transfer which significantly affected the live birth outcome. Woman age, number of eggs collected and achieving cryopreservation of surplus embryos had no statistically significant effect on treatment outcome.

CONCLUSIONS

The live birth outcome of PGD cycles for serious genetic disorder is modest and is affected by the number of embryos genetically suitable for transfer.

Indications et résultats du diagnostic pré-implantatoire (DPI)

OBJECTIVE

To report the results of preimplantation genetic diagnosis (PGD) cycles performed in our unit from 2000 to 2004. Materials and methods. One hundred and seventy-one couples were enrolled in the PGD program over this period. The collected oocytes were inseminated by intracytoplasmic sperm injection (ICSI). The resulting embryos were biopsied on the third day of development and the genetic analysis was performed on the same day. Embryo transfers were carried out on the fourth day.

RESULTS

The 416 stimulation cycles started yielded 280 oocyte pick-ups, 3506 oocytes retrieved, of which 2966 were suitable for ICSI. Among the 1982 embryos obtained, 1337 embryos were biopsied and genetic diagnosis was performed for 1083 (81%) of them. 381 embryos were transferred during the course of 189 transfer procedures. There were 51 clinical and 46 ongoing (35 single, 11 twin) pregnancies. In addition, 25 frozen embryo replacement cycles were initiated, leading to 6 embryo transfers and 1 ongoing pregnancy. A total of 58 unaffected children were born.

CONCLUSION

PGD has gained a place among the choices offered to couples at risk of transmission of a serious and incurable genetic disease. It might be a realistic alternative to prenatal diagnosis for patients carrier of chromosomal rearrangements, single gene defects, X-linked disesases or mitochondrial DNA disorders.

Embryo aneuploidy screening for repeated implantation failure and unexplained recurrent miscarriage

Among other factors, chromosomal abnormalities that originate from gametogenesis and preimplantation embryonic development are thought to be one of the major contributing factors for early embryonic death and failure of pregnancy. However, so far, no non-invasive technique exists that allows the detection of the chromosomal complement of an oocyte or a developing embryo as a whole. Rather, by removing polar bodies/blastomeres, recent developments on preimplantation genetic diagnosis for aneuploidy screening (PGD-AS) have paved the way to detect and possibly eliminate the majority of chromosomally abnormal embryos, thereby increasing the chance of a healthy pregnancy. This article summarizes the origin and impact of chromosomal abnormalities on human reproduction in cases with repeated implantation failure (RIF) and unexplained recurrent miscarriage. It also discusses recent advances regarding the possible benefits of PGD-AS in such cases.

Validation of DNA probes for preimplantation genetic diagnosis (PGD) by fluorescencein situ hybridization (FISH) R1

BACKGROUND

Preimplantation genetic diagnosis (PGD) by fluorescence in situ hybridization (FISH) is being employed increasingly by medical centers and private companies. Validation of any clinical assay, particularly one with novel applications such as PGD by FISH, is of critical importance in the clinical setting. This importance is recognized by both the College of American Pathologists (CAP) and the American College of Medical Genetics (ACMG), who recommend validation of FISH assays in the clinical setting. Validation of FISH assays for PGD is especially significant, as only one or two cells (blastomeres) will be available for testing of a given embryo.

METHODS

We have developed validation protocols for a variety of FISH assays, including sex identification, structural chromosomal aneusomy, and aneuploidy screening with the Vysis, Inc., PGT probe panel.

RESULTS

Our validation results show good individual performance of commercially available probes, and decreasing overall efficiency as the number of probes included in an assay increases.

Preimplantation genetic diagnosis as a novel source of embryos for stem cell research

The generation of human embryonic stem (hES) cells has captured the public and professional imagination, largely due their potential as a means of overcoming many debilitating and degenerative diseases by cell replacement therapy. Despite this potential, few well-characterized hES cell lines have been derived. Indeed, in the UK, despite several centres having been active in this area for more than 2 years, there are as yet no published reports of human embryonic stem cells having been generated. Part of the reason for this lack of progress may relate to the quality of embryos available for research. Embryos surplus to therapeutic requirements following routine assisted reproduction treatment are often of poor quality and a large proportion may be aneuploid. This study reports a new approach to hES cell derivation. Embryos surplus to therapeutic requirements following preimplantation genetic diagnosis were used. Although unsuitable for embryo transfer due to the high risk of genetic disease, these embryos are from fertile couples and thus may be of better quality than fresh embryos surplus to assisted reproduction treatment cycles. Embryos donated after cryopreservation were also used, and putative hES lines were derived from both sources of embryos. The cell lines described here are thought to be the first reported hES cell lines to have been derived in the UK.

Comparison between fluorescence in situ hybridization (FISH) and quantitative-fluorescent polymerase chain reaction (QF-PCR) for the detection of aneuploidies in single blastomeres

OBJECTIVES

The aim of our investigation was to compare the efficiencies of the fluorescence in situ hybridization (FISH) and the quantitative-fluorescent PCR (QF-PCR) methods for the detection of sexing and numerical chromosome disorders in single blastomeres collected from the same preimplantation human embryos.

METHODS

FISH analysis was carried out on 145 blastomeres from the 79 surplus embryos with probes specific for chromosomes 13, 18, 21, X, and Y. QF-PCR was performed with each one or two of the primers specific for the same chromosomes on 151 blastomeres from the same embryos obtained from patients undergoing IVF treatment.

RESULTS

Analyses were possible on 135 blastomeres (93%) by FISH and on 117 blastomeres (77%) by QF-PCR. Of 65 embryos, which could be analyzed by both methods, 20 embryos (31%) were diagnosed as abnormal.

CONCLUSION

The present study shows that FISH tests are more accurate than QF-PCR assays for the detection of numerical chromosome disorders when performed on single blastomeres.

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.

Chromosomal information derived from single blastomeres isolated from cleavage-stage embryos and cultured in vitro

OBJECTIVE

To evaluate the potential of proliferation of single blastomeres isolated from human cleavage-stage embryos for use in preimplantation genetic diagnosis of chromosomal abnormalities.

DESIGN

A laboratory study of chromosomal content of blastomeres isolated from embryos of patients from an in vitro fertilization program.

SETTING

University hospital laboratory.

PATIENT(S)

Couples undergoing IVF or ICSI.

INTERVENTION(S)

Blastomeres were isolated from normally fertilized cleavage-stage human embryos, cultured in vitro or fixed immediately, and analyzed by fluorescence in situ hybridization (FISH) probes.

MAIN OUTCOME MEASURES

Chromosomal information yielded by blastomeres cultured in vitro compared with those obtained from blastomeres that were processed for chromosomal analysis directly after isolation.

RESULT(S)

The percentage of cultured blastomeres that produced FISH results was significantly lower than the percentage of blastomeres processed for FISH directly after isolation (72% vs. 90%). Lack of FISH results from cultured cells, which in most cases was related to nuclear anomalies, was significantly more frequent among nondivided than divided blastomeres (39% vs. 21%). Both cultured and noncultured cells showed diploid, aneuploid and polyploid chromosome complements on FISH. Compared with directly processed cells, cultured cells yielded a higher proportion of polyploid patterns (22.9% vs. 6.1%). Of the cultured blastomeres that divided, 18% produced progeny with mosaicism.

CONCLUSION(S)

Although blastomere culture may increase the number of cells available for chromosomal analysis, the high frequency of nuclear defects and the occurrence of polyploidy and mosaicism among cultured cells discourage the use of blastomere isolation and proliferation strategy for use in preimplantation genetic diagnosis.

Ethics of preimplantation diagnosis: recordings from the Fourth International Symposium on Preimplantation Genetics

New ethical issues emerge from the rapid expansion in knowledge of preimplantation genetics. These were summarized and debated recently during the final session at the Fourth International Symposium on Preimplantation Genetics, held in Cyprus, 10-13 April 2002. Divergent views were expressed on various topics including unique issues in preimplantation genetic diagnosis, the sexing of embryos, cloning and other matters. Differing ethical viewpoints emerged, and alternative ways of coping with certain issues were described. This complex area of ethical and social issues will demand detailed counselling of patients, ongoing debate among professionals, and perhaps legislation or central regulatory authorities to decide on the detailed application of its new technologies.

Strategies and outcomes of the first 100 cycles of preimplantation genetic diagnosis at the Guy's and St. Thomas' Center

OBJECTIVE

To establish strategies for the implementation of a successful preimplantation genetic diagnosis (PGD) service.

DESIGN

Retrospective review of data from a single center.

SETTING

A United Kingdom National Health Service hospital.

PATIENT(S)

Patients (60 couples) were referred for PGD from UK genetic centers.

INTERVENTION(S)

We followed the protocol of ovarian stimulation, oocyte retrieval, fertilization, single cell biopsy on day 3, and embryo transfer on day 4. Pregnancies unaffected by the familial genetic condition.

RESULT(S)

A total of 60 couples was treated for 20 different conditions. Early cycles using nonsequential embryo culture media were less successful (13% pregnancy rate/embryo transfer) than later cycles using sequential media (33.5%). Ninety-four percent of embryos (n = 473) had a single cell removed at biopsy. The overall pregnancy rate was 24% per cycle started, 29% per egg collection, 38% per transfer, and 40% per couple treated. In one cycle, an affected pregnancy followed PGD for spinal muscular atrophy (SMA).

CONCLUSION(S)

The use of sequential media and single cell biopsy results in a successful PGD program with encouraging pregnancy rates.

Meiotic outcomes in reciprocal translocation carriers ascertained in 3-day human embryos

Chromosomes involved in reciprocal translocations form quadrivalents at meiosis. These quadrivalents segregate, with or without recombination, to give 32 different meiotic outcomes, only two of which are normal or balanced. This paper presents data collected from 25 cycles of preimplantation genetic diagnosis for 18 couples carrying 15 different reciprocal translocations. Embryos were tested using fluorescence in situ hybridisation with probes for the translocated and centric segments. Overall, 47.7% (71 out of 149) of embryos tested showed signal patterns consistent with alternate segregation, 24.8% adjacent-1 segregation, 10.1% adjacent-2 segregation, 15.4% 3 : 1 segregation and 2% 4 : 0 segregation. For most translocations, alternate segregation was apparently the most frequent mode. Alternate and adjacent-1 frequencies were similar in male and female carriers; however, 5.7% of embryos from female translocation carriers showed adjacent-2 segregation and 20.0% showed 3 : 1 segregation, whilst the corresponding figures for male carriers were 20.5 and 4.5%. Overall, 2.8% of embryos were mosaic and 2.3% of embryos showed chaotic constitutions for the chromosomes tested. The pregnancy success rate for these 25 cycles was 38.8% per embryo transfer and also 38.8% per couple.

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) is an evolving technique that provides a practical alternative to prenatal diagnosis and termination of pregnancy for couples who are at substantial risk of transmitting a serious genetic disorder to their offspring. Samples for genetic testing are obtained from oocytes or cleaving embryos after in vitro fertilization. Only embryos that are shown to be free of the genetic disorders are made available for replacement in the uterus, in the hope of establishing a pregnancy. PGD has provided unique insights into aspects of reproductive genetics and early human development, but has also raised important new ethical issues about assisted human reproduction.

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: applications for molecular medicine

Preimplantation genetic diagnosis is an alternative to prenatal diagnosis for the detection of genetic disorders. Tests are conducted on single cells biopsied from embryos before they are implanted, allowing the selection of unaffected embryos before a pregnancy has been established. Thus, the issue of pregnancy termination is circumvented. The use of preimplantation genetic diagnosis might have a significant impact on in vitro fertilization success rates as well as allowing the diagnosis of inherited disease.