Successful outcome with day 4 embryo transfer after preimplantation diagnosis for genetically transmitted diseases

The enigmatic morula: mechanisms of development, cell fate determination, self-correction and implications for ART

BACKGROUND

Assisted reproduction technology offers the opportunity to observe the very early stages of human development. However, due to practical constraints, for decades morphological examination of embryo development has been undertaken at a few isolated time points at the stages of fertilisation (Day 1), cleavage (Day 2-3) and blastocyst (Day 5-6). Rather surprisingly, the morula stage (Day 3-4) has been so far neglected, despite its involvement in crucial cellular processes and developmental decisions.

OBJECTIVE AND RATIONALE

The objective of this review is to collate novel and unsuspected insights into developmental processes occurring during formation of the morula, highlighting the key importance of this stage for a better understanding of preimplantation development and an improvement of ART.

SEARCH METHODS

PubMed was used to search the MEDLINE database for peer-reviewed English-language original articles and reviews concerning the morula stage in mammals. Searches were performed by adopting 'embryo', 'morula', 'compaction', 'cell fate' and 'IVF/assisted reproduction' as main terms, in association with other keywords expressing concepts relevant to the subject (e.g. cell polarity). The most relevant publications, i.e. those concerning major phenomena occurring during formation of the morula in established experimental models and the human species, were assessed and discussed critically.

OUTCOMES

Novel live cell imaging technologies and cell biology studies have extended our understanding of morula formation as a key stage for the development of the blastocyst and determination of the inner cell mass (ICM) and the trophectoderm (TE). Cellular processes, such as dynamic formation of filopodia and cytoskeleton-mediated zippering cell-to-cell interactions, intervene to allow cell compaction (a geometrical requisite essential for development) and formation of the blastocoel, respectively. At the same time, differential orientation of cleavage planes, cell polarity and cortical tensile forces interact and cooperate to position blastomeres either internally or externally, thereby influencing their cellular fate. Recent time lapse microscopy (TLM) observations also suggest that in the human the process of compaction may represent an important checkpoint for embryo viability, through which chromosomally abnormal blastomeres are sensed and eliminated by the embryo.

WIDER IMPLICATIONS

In clinical embryology, the morula stage has been always perceived as a 'black box' in the continuum of preimplantation development. This has dictated its virtual exclusion from mainstream ART procedures. Recent findings described in this review indicate that the morula, and the associated process of compaction, as a crucial stage not only for the formation of the blastocyst, but also for the health of the conceptus. This understanding may open new avenues for innovative approaches to embryo manipulation, assessment and treatment.

Morula transfer achieves better clinical outcomes than post-thawed cleavage embryos after overnight culture in frozen embryo transfer (FET) cycles

PURPOSE

This study aimed to investigate the clinical outcomes of morula stage transfer derived from post-thawed cleavage embryos undergoing overnight culture in frozen embryo transfer (FET) cycles.

METHODS

We performed a retrospective study that included 392 FET cycles with 784 thawed embryos undergoing overnight culture between January 2014 and December 2018. Embryos were divided into three groups in terms of their status: 8-16 cells without morula (group I), one morula (group II), and two morulae (group III). The clinical outcomes of these cycles were then compared between the three groups. Logistic regression analysis was performed to control for confounders.

RESULTS

Group III was associated with a significantly higher clinical pregnancy rate (odds ratio [OR] 2.35; 95% confidence interval [CI] 1.29-4.27; P = 0.005), implantation rate (OR 3.00; CI 1.75-5.16; P < 0.001), multiple pregnancy rate (OR 4.91; CI 2.11-11.40; P < 0.001), and live birth rate (OR 1.96; CI 1.10-3.49; P = 0.022) than group I. Group II had a higher live birth rate than group I after adjustment (OR 1.70; CI 1.04-2.79; P = 0.035). There was no difference in the rate of premature delivery when compared across the three groups after adjustment.

CONCLUSION

The transfer of morula stage embryos following the overnight culture of post-thawed cleavage embryos led to an improvement in the clinical outcomes of FET cycles. It is important to reduce the number of morula embryos transferred in order to achieve a singleton pregnancy.

Pregnancy rates of day 4 and day 5 embryos after culture in an integrated time-lapse incubator

BACKGROUND

The aim of this study was to compare pregnancy rates in patients undergoing IVF/ICSI with embryo transfer after 4 and 5 days of culture in a closed incubation system with integrated time-lapse imaging.

METHODS

Out of n = 2207 in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI) cycles performed between January 2011 and April 2016 at a tertiary referral university hospital, a total of n = 599 IVF/ICSI cycles with prolonged embryo culture in an integrated time-lapse system (EmbryoScope^© (Vitrolife)) until day 4 or 5 were retrospectively analyzed with regard to embryo morphology and pregnancy rates.

RESULTS

A transfer on day 5 compared to a transfer on day 4 did not result in higher implantation and clinical pregnancy rates (IR 29.4% on day 4 versus 33.0% on day 5, p = 0.310; CPR 45.2% on day 4 versus 45.7% on day 5, p = 1.0). The percentage of ideal embryos transferred on day 4 was comparable to the rate of ideal embryos transferred on day 5 (41.6% versus 44.1%, p = 0.508). However, on day 4 a significantly higher number of embryos was transferred (1.92 on day 4 versus 1.84 on day 5, p = 0.023), which did not result in higher rates of multiple pregnancies.

CONCLUSIONS

Pregnancy rates in IVF/ICSI cycles with integrated time-lapse incubation and transfer on day 4 and 5 are comparable. This finding provides the clinician, IVF laboratory and patient with more flexibility.

TRIAL REGISTRATION

This study was retrospectively registered by the local ethics committee of the University of Heidelberg on December 19, 2016 (registration number S-649/2016).

Morphological assessment on day 4 and its prognostic power in selecting viable embryos for transfer

The aim of this study was to describe a system for embryo morphology scoring at the morula stage and to determine the efficiency of this model in selecting viable embryos for transfer. In total, 519 embryos from 122 patients undergoing intracytoplasmic sperm injection (ICSI) were scored retrospectively on day 4 according to the grading system proposed in this article. Two separate quality scores were assigned to each embryo in relation to the grade of compaction and fragmentation and their developmental fate was then observed on days 5 and 6. Secondly, the prediction value of this scoring system was compared with the prediction value of the traditional scoring system adopted on day 3. Morulas classified as grade A showed a significant higher blastocyst formation rate (87.2%) compared with grades B, C and D (63.8, 41.3 and 15.0%, respectively), (P < 0.001). Furthermore, the ability to form top quality blastocysts was significantly higher for grade A morulas with respect to grades B, and C and D (37.8% vs. 22.4% vs. 11.1%), (P < 0.001). Finally, the morula scoring system showed more prediction power with respect to the embryo scoring a value of 1 [Akaike information criterion (AIC) index 16.4 vs. 635.3 and Bayesian information criterion (BIC) index −68.8 vs. −30.0 for morulas and embryos respectively]. In conclusion, results demonstrated that the presented scoring system allows for the evaluation of eligible embryos for transfer as a significant correlation between the grade of morula, blastulation rate and blastocyst quality was observed. Furthermore, the morula scoring system was shown to be the best predictive model when compared with the traditional scoring system performed on day 3.

Clinical outcomes of elective single morula embryo transfer versus elective single blastocyst embryo transfer in IVF-ET

PURPOSE

To compare the clinical outcomes of elective single morula embryo transfer (eSMET) versus elective single blastocyst embryo transfer (eSBET) in selected patients.

METHODS

This study was a retrospective study which analyzed for 271 cycles in women under 37 years of age who are undergoing their first or second trial of in vitro fertilization-embryo transfer (IVF-ET) from January 2008 to December 2009. The eSMET was performed on day 4 (n = 130) and the eSBET was conducted on day 5 (n = 141).

RESULTS

The clinical pregnancy rate (51.5% vs. 51.8%, p = 0.97), implantation rate (52.3% vs. 52.5%, p = 0.98), and live birth rate (39.2% vs. 44.7%, p = 0.36) were similar in the eSMET and eSBET groups, respectively. The miscarriage rate of the eSMET group (23.9%) was slightly higher than that of the eSBET group (13.7%) (p = 0.12), without reaching statistical significance. There was only one case of monozygotic twin pregnancy in each group.

CONCLUSIONS

The clinical outcomes of day 4 eSMET were comparable to those of day 5 eSBET. Therefore, day 4 eSMET is a viable option or an alternative to day 5 eSBET, with no difference in success rates.

Day 4 versus day 3 embryo transfer: a prospective study of clinical outcomes

OBJECTIVE

To compare the clinical outcomes after day 4 or day 3 embryo transfers in controlled ovarian hyperstimulation-IVF/intracytoplasmic sperm injection (ICSI) cycles.

DESIGN

Prospective randomized study.

SETTING

Center for Human Reproduction, 'Genesis Athens' Clinic (private gynecological and surgical clinic), Athens, Greece.

PATIENT(S)

Three hundred fifty women with primary infertility and indication for IVF/ICSI treatment. Patients were randomly allocated to day 4 or day 3 embryo transfer.

INTERVENTION(S)

Controlled ovarian hyperstimulation, oocyte retrieval, IVF/ICSI, embryo transfer.

MAIN OUTCOME MEASURE(S)

Implantation rate; clinical, ongoing, and multiple pregnancy rates.

RESULT(S)

A trend toward higher clinical and ongoing pregnancy rates was noted after day 4 embryo transfers. Implantation and multiple pregnancy rates were comparable after day 4 or day 3 embryo transfers.

CONCLUSION(S)

The transfer of day 4 embryos in IVF/ICSI cycles may result in favorable implantation and pregnancy rates which are at least comparable to those after the transfer of day 3 embryos.

Blastocyst biopsy versus cleavage stage biopsy and blastocyst transfer for preimplantation genetic diagnosis of β-thalassaemia: a pilot study

BACKGROUND

Trophectoderm biopsy at the blastocyst stage is an emerging approach in preimplantation genetic diagnosis (PGD). This study aimed to compare genotyping success and implantation rates in PGD cycles for beta-thalassaemia following biopsy at the cleavage versus the blastocyst stage, with transfer of blastocysts.

METHODS

This pilot study included 20 cycles: Group A: 10 cycles, day 3 blastomere biopsy, day 5 transfer; Group B: 10 cycles, day 5 trophectoderm biopsy, day 6 transfer. Standard-assisted reproduction and laser biopsy procedures were used. Biopsied cells were genotyped using real-time PCR multiplexed with fluorescent microsatellite analysis.

RESULTS

In Group A, 131 fertilized eggs developed to 101 embryos suitable for single blastomere biopsy; 76/101 blastomeres were diagnosed (75.2%), 30 unaffected blastocysts were transferred resulting in six pregnancies (eight fetal hearts, 26.7% implantation rate). In Group B, 128 fertilized eggs developed to 53 blastocysts for trophectoderm biopsy (four to five cells), with 50/53 blastocysts diagnosed (94.3%), 21 unaffected blastocysts transferred and 6 pregnancies initiated (10 fetal hearts, 47.6% implantation rate). Overall, nine pregnancies reached >10 weeks gestation and were confirmed unaffected by prenatal diagnosis, with 12 healthy babies born.

CONCLUSIONS

This pilot study suggests that trophectoderm biopsy and blastocyst transfer may be more advantageous than cleavage stage biopsy with respect to outcome of PGD for monogenic diseases.

Successful pregnancy rates achieved with day 4 embryo transfers

OBJECTIVE

To assess the success of day 4 embryo transfers (ETs) following IVF at one institution.

DESIGN

Retrospective analysis.

SETTING

A university hospital IVF program.

PATIENT(S)

Two hundred nondonor, fresh IVF cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE

Outcomes of IVF. Outcome assessments after day 4 ETs included rates of implantation, clinical pregnancy, and singleton and multiple live births.

RESULT(S)

The overall live-birth rate was 54.4%. Implantation rates were highest in younger age groups, and similar in patients 35-40 years of age. Pregnancy and live-birth rates were similar across all age groups up to age 40 years. Multiple gestations were highest in women < or =40 years of age.

CONCLUSION

Acceptable pregnancy rates can be achieved with day 4 ETs.

Preimplantation genetic diagnosis for Marfan syndrome

OBJECTIVE

To develop and apply efficient and reliable protocols for preimplantation genetic diagnosis (PGD) for Marfan syndrome.

DESIGN

Two mutation-specific protocols were developed, and the markers D15S1028, D15S992, D15S196, D15S576, D15S123, and D15S143 were used to set up four multiplex polymerase chain reactions (PCRs).

SETTING

Research Center Reproduction and Genetics.

PATIENT(S)

Ten couples carrying mutations in the FBN1 gene.

INTERVENTION(S)

Six PGD protocols were developed for 10 couples, and 7 of them underwent a total of 16 clinical cycles.

MAIN OUTCOME MEASURE(S)

Amplification, allele drop-out (ADO), and contamination rates during the preclinical assays. DNA analyses of blastomeres from embryos biopsied during PGD cycles.

RESULT(S)

Six different protocols were set up, with the main objective being to to use one protocol for several couples. A total of 16 PGD cycles were performed, which resulted in the delivery of an unaffected boy and three ongoing pregnancies.

CONCLUSION(S)

The development of single-cell multiplex PCRs for linked markers and its use in PGD reduce the workload of the genetic diagnostic laboratory as well as the average waiting time for patients. This approach also allows for the simultaneous and accurate detection of recombination, contamination, and ADO, thereby increasing the reliability of the diagnosis.

Preimplantation Genetic Diagnosis:

Preimplantation genetic diagnosis (PGD) can provide genetic information on embryos obtained through in vitro fertilization (IVF), allowing implantation of embryos identified as unaffected with a given genetic or chromosomal disorder. With the availability of increasingly sophisticated genetic testing, its use has advanced from the selection of female embryos for the prevention of X-linked genetic diseases to testing for single gene disorders via PCR. Recently, PGD has also been used in the setting of assisted reproductive technology to select for chromosomally normal embryos in an effort to increase the rates of implantation and successful pregnancy. As the number of patients undergoing IVF increases, the indications for its use broadens, and more mutations underlying genetic disorders are identified, PGD is becoming more widespread. As this evolution continues, recognition of the limitations of PGD, as well as ethical concerns regarding use and misuse of this technology, need to be considered by patients, clinicians, and policy makers.

Birth of a healthy infant following trophectoderm biopsy from blastocysts for PGD of beta-thalassaemia major

PGD is a well accepted reproductive choice for couples at genetic risk and involves the diagnosis and transfer of unaffected IVF embryos. PGD for monogenetic diseases is most commonly accomplished by the biopsy of one or two blastomeres from cleavage stage embryos, followed by PCR-based protocols. However, PCR-based DNA analysis of one or two cells is subject to several problems, including total PCR failure, or failure of one allele to amplify. Trophectoderm biopsy at the blastocyst stage enables the removal of more than two cells for diagnosis while being non-invasive to the inner cell mass which is destined for fetal development. The aim of this study was to develop a safe, reliable technique for the biopsy of trophectoderm cells from human blastocysts. This case report demonstrates that removal of trophectoderm cells prior to blastocyst transfer is compatible with implantation and development to term. Here we report successful PGD for beta-thalassaemia following trophectoderm cell biopsy from blastocysts and the birth of a healthy infant.

ESHRE PGD Consortium ‘Best practice guidelines for clinical preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS)’

Among the many educational materials produced by the European Society of Human Reproduction and Embryology (ESHRE) are guidelines. ESHRE guidelines may be developed for many reasons but their intent is always to promote best quality practices in reproductive medicine. In an era in which preimplantation genetic diagnosis (PGD) has become a reality, we must strive to maintain its efficacy and credibility by offering the safest and most effective treatment available. The dominant motivators for the development of current comprehensive guidelines for best PGD practice were (i) the absence of guidelines and/or regulation for PGD in many countries and (ii) the observation that no consensus exists on many of the clinical and technical aspects of PGD. As a consequence, the ESHRE PGD Consortium undertook to draw up guidelines aimed at giving information, support and guidance to potential, fledgling and established PGD centres. The success of a PGD treatment cycle is the result of great attention to detail. We have strived to provide a similar level of detail in this document and hope that it will assist staff in achieving the best clinical outcome for their patients.

Improved implantation after preimplantation genetic diagnosis of aneuploidy

The objective of this study was to assess the improvement in implantation rates after preimplantation genetic diagnosis (PGD) of numerical abnormalities for the sole indication of advanced maternal age when compared with a control group. Each PGD patient was matched to a control patient according to several parameters prior to obtaining pregnancy results. The diagnosis was based on the analysis of chromosomes X, Y, 13, 15, 16, 18, 21 and 22 plus a ninth probe (1, 7, 14 or 17) on a single cell per embryo. The results were also analysed in relation to the previous number of IVF cycles and the number of dipronucleated zygotes obtained, when replacing presumptively chromosomally normal embryos on day 4 of development. It was found that women of advanced reproductive age (average age 40 years) had a higher implantation rate (18%) than their matched controls treated with standard IVF (11%) (P < 0.05). This increase was not observed in patients with two or more previous IVF cycles or patients with fewer than eight zygotes. Patients with eight or more 2PN zygotes and one or no previous cycles showed the greatest improvement in implantation rate, from 8.8% in controls to 19.2% in the PGD group (average age 40 years) (P < 0.025).

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.

Living with Marfan syndrome III. Quality of life and reproductive planning

As individuals with Marfan syndrome are increasingly diagnosed earlier in life and prior to life-threatening cardiovascular events, there is opportunity to study factors that influence their reproductive planning and quality of life. In this study of 174 affected adults, the overall quality of life was reported to be adequate, although it was significantly decreased within the spiritual/psychological domain. Approximately 62% agreed that having Marfan syndrome significantly affected their reproductive decision-making. This view was correlated with age of diagnosis, mitral valve prolapse, and the view that Marfan syndrome has adverse consequences on life. Sixty-nine percent reported personal interest in prenatal testing for Marfan syndrome. Respondents most commonly cited increased worries about personal health and the recurrence risk as ways that Marfan syndrome affects their reproductive decisions. Age, striae, back pain, and low quality of life were each independently correlated with lack of sex drive. These results affirm the importance of both clinical and psychosocial issues on affected adults' reproductive decision-making and sexual well-being. Genetic professionals are ideally positioned to discuss concerns about quality of life and reproduction with patients with Marfan syndrome and refer those with significant concerns for further evaluation and management.

The neglected morula/compact stage embryo transfer

BACKGROUND

This retrospective study analysed the outcomes of 339 embryo transfers on either day 3 (n = 97) or day 4 (n = 242), and proposed a grading system for morula/compact embryos.

METHODS

The morula/compact embryo grading was based on: (i) the proportion of blastomeres undergoing the compaction process; (ii) the morphology of the compacted multicellular mass; (iii) the embryo quality on day 2 and 3; and (iv) the amount of fragmentation. Embryo transfers were classified into groups as follows: group I: transferred with zero 'good' embryos; group II: one 'good' embryo; group III: two or more 'good' embryos.

RESULTS

Patients on day 4 were transferred with significantly fewer embryos in groups II and III (2.58 +/- 0.9 and 2.35 +/- 0.6 respectively) when compared with the correspondent day 3 transfers (3.81 +/- 1.4 and 4.07 +/- 0.9 respectively) (P < 0.05), but had the same or higher implantation and pregnancy rates. Analysing the patients who had transfers with all 'good' embryos, day 4 transfer achieved a significantly higher implantation rate compared with day 3 transfer (46.4 versus 21.4%, P < 0.01), but the number of embryos transferred on day 4 was significantly lower than day 3 (2.1 +/- 0.5 versus 3.5 +/- 0.9, P < 0.01).

CONCLUSIONS

The morula/compact embryos had great value for embryo selection, which significantly reduced the number of embryos needed for transfer.

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.

The use of preimplantation genetic diagnosis in sex selection for family balancing in India

This paper describes the use of preimplantation genetic diagnosis (PGD) in sexing embryos for family balancing in a private IVF clinic in India from April 1999 to April 2001. Embryos were biopsied and analysed on day 3, cultured in sequential media and then transferred on day 4 or day 5 after morphological selection of the best embryos. From a total of 42 cycles started, 14 clinical pregnancies and nine live births have been achieved so far, with five ongoing pregnancies. The benefits of delayed transfer 24-48 h after the embryo biopsy are that PGD centres could use the extra time available to confirm the diagnosis or introduce additional diagnostic tests for the same embryo. The selection of blastocysts for transfer should also permit the transfer of fewer embryos, thus reducing the risk of multiple gestations and increasing the pregnancy rate as a consequence of the expected higher implantation rate. This is the first report of the use of PGD in sex selection for family balancing in India, where couples place a premium on having baby boys, and the social and ethical aspects of the use of this technology in this setting are briefly discussed.

Direct comparison of detection systems used for the development of single-cell genetic tests in preimplantation genetic diagnosis

PURPOSE

Single-cell polymerase chain reaction (PCR) requires efficient amplification and accurate detection. We compare the accuracy of heteroduplex, fluorescent-fragment, and fluorescent single-strand conformation polymorphism (F-SSCP) analysis as detection systems for analysis of a PCR assay developed for preimplantation genetic diagnosis.

METHODS

A single-cell, fluorescent multiplex PCR assay was developed for the cystic fibrosis delta F508 mutation and the short tandem repeat, D21S11. Detection systems were compared by analyzing blinded PCR products.

RESULTS

Amplification rates for cystic fibrosis were 89% by heteroduplex and 91% by fragment analysis, while it was 72% for D21S11 by fragment analysis. No difference in allele dropout was detected for cystic fibrosis by any method (2%). Overall accuracy was high, > 97%, although SSCP was the least accurate.

CONCLUSIONS

Heteroduplex and fragment analysis proved equal in the diagnosis of a single amplified locus. We determined that fragment analysis allows maximal accuracy of detection and permits analysis of a second loci, controlling for DNA contamination and allelic dropout.

First specific preimplantation genetic diagnosis for ornithine transcarbamylase deficiency

Ornithine transcarbamylase (OTC) deficiency is an X-linked dominant metabolic disorder with partial penetrance in heterozygous females. Affected boys usually die from hyperammonemia in the first few days of life, while clinical expression in carrier females ranges from no symptoms to neonatal death. A young couple whose boy had died of OTC deficiency in the neonatal period was referred to our genetic department for their subsequent pregnancy. The fetus was found to be affected, and after genetic counseling the pregnancy was terminated. Prenatal diagnosis of the third pregnancy identified a heterozygous female, who died after a normal birth at age 11 days from hyperammonemia. After this, the couple asked for preimplantation genetic diagnosis (PGD). We have developed a duplex nested PCR assay allowing the amplification of both the mutation and an informative restriction fragment length polymorphism (RFLP) located in the 3' end of the OTC gene. After nested amplification, allele identification was carried out for both loci by double restriction digestion and electrophoresis gel analysis. The co-amplification of both loci provided a means of detecting potential allele dropout or incomplete digestion. Two PGD cycles were carried out, a total of 14 embryos were analysed and a diagnosis could be obtained in 13/14 embryos. There were four unaffected male embryos, four heterozygous females and four unaffected females; the final embryo was an affected one of undetermined gender. In both cycles, three unaffected embryos could be transferred early on Day 4 post-insemination. The second cycle resulted in the birth of a baby boy devoid of the OTC mutation. This constitutes the first birth following PGD carried out by a French team.

Reduced survival after human embryo biopsy and subsequent cryopreservation

Preimplantation genetic diagnosis (PGD) is performed in couples at risk of genetic disease, so as to avoid transfer of embryos which are affected by a monogenic disease or which carry chromosomal aberrations. As in all in-vitro fertilization (IVF) cycles, supernumerary non-affected good-quality embryos may be available after PGD. These embryos can be cryopreserved. So far, limited data on survival after cryopreservation of biopsied human embryos are available. In this study, human embryos of good morphological quality derived from abnormal fertilization were used to evaluate the influence of the embryo biopsy procedure on survival after cryopreservation. Embryos were allocated to three different groups: control (n = 20), drilling-only (n = 16), and biopsy (n = 29). After freezing and thawing, a significantly lower number of blastomeres was intact in the drilling-only group (46/118, i.e. 39.0%, P < 0.01) and in the embryo biopsy group (46/156, i.e. 29.5%, P < 0.0001) than in the control group (85/151, i.e. 56.3%). This difference was reflected in survival rates of embryos. Fifty-five per cent of the control embryos, 37.5% of the drilling-only group, and 33.3% of the biopsy group had at least 50% of their blastomeres intact. After further in-vitro culture, four blastocysts, three from the drilling-only group and one from the biopsy group, developed from the surviving embryos. From this study it can be concluded that current cryopreservation procedures are less successful when biopsied human embryos are cryopreserved, but that surviving embryos can develop to the blastocyst stage and thus may have the potential to develop to term.

Advantages of day 4 embryo transfer in patients undergoing preimplantation genetic diagnosis of aneuploidy

PURPOSE

Following preimplantation genetic diagnosis of aneuploidy, embryo transfer was executed on day 4, with the aim of providing more time for expanding from six to nine the number of diagnosed chromosomes per single cell (Group 2; 45 cycles). The results obtained were compared to those derived from conventional day 3 transfer (Group 1; 71 cycles).

METHODS

For multicolor fluorescence in situ hybridization analysis, two panels of probes were used: the first, specific for chromosomes XY, 13, 16, 18, and 21, was tested in all patients (Groups 1 and 2); the second was implemented only in Group 2 patients for the detection of chromosomes 14, 15, and 22.

RESULTS

A total of 406 embryos underwent fluorescence in situ hybridization analysis in Group 1, and 236 in Group 2. Comparable percentages of both chromosomal abnormalities (61% and 62%) and pregnancy and implantation rates (36% and 24.5% in Group 1, 41% and 23.6% in Group 2) resulted, regardless of the higher mean age in Group 2.

CONCLUSIONS

The diagnosis of the nine chromosomes which are most frequently associated with aneuploidy in humans could have an immediate impact on the rate of spontaneous abortions. Additional advantages are represented by the more accurate morphological evaluation of euploid embryos; the advanced compaction, which means that embryos are less exposed to damage during the transfer procedure; and the possibility of performing a reanalysis in cases where a fluorescence in situ hybridization diagnosis is not obtained.