Clinical Considerations of Preimplantation Genetic Diagnosis for Monogenic Diseases

A mathematical model for predicting the number of transferable blastocysts in next-generation sequencing-based preimplantation genetic testing

PURPOSE

To investigate the clinical factors that could be used predict the number of transferable blastocysts in preimplantation genetic testing (PGT) cycles based on next-generation sequencing (NGS) and formed form a mathematical model to predict the chance likelihood of obtaining one transferable blastocyst, which is helpful for genetic counseling.

METHODS

This retrospective study enrolled couples undergoing PGT cycles for chromosomal structural rearrangement (PGT-SR, n = 363, 202 with reciprocal translocation carriers, 131 with Robertsonian translocation carriers, 30 with inversion carriers), monogenic diseases (PGT-M, n = 47), and for Aneuploidies (PGT-A, n = 132) from January 2015 to October 2018. Stepwise multiple linear regression analysis was used to identify the factors relevant for obtaining at least one transferable blastocyst. The factors that predict the number of biopsied blastocysts were further analyzed.

RESULTS

The transferable blastocyst rates were 29.94, 41.99, 49.09, 41.42, and 44.37% in the reciprocal translocation carrier, Robertsonian translocation carrier, inversion carrier, PGT-M, and PGT-A cycles, respectively. The number of transferable blastocysts in these cycles were 0.3004 × the number of biopsied blastocysts (NBB) - 0.0031, 0.4063 × NBB + 0.0460, 0.5762 × NBB - 0.3128, 0.3611 × NBB + 0.1910, and 0.4831 × NBB - 0.0970, respectively. Furthermore, the number of MII oocytes and female age were clinical predictors of NBB in reciprocal translocation and PGT-A couples, while the number of MII oocytes was the only clinical predictor in Robertsonian translocation carriers, inversion carriers, and PGT-M couples.

CONCLUSIONS

The number of biopsied blastocysts was the only clinical predictor of the ability to obtain a transferable blastocyst in PGT cycles; therefore, for clinical practice, theoretically the minimum numbers of biopsied blastocysts is 4 in reciprocal translocation carrier and 3 in couples undergoing PGT for other reasons. The number of MII oocytes and female age were clinical predictors of the number of biopsied blastocysts. With the mathematical models in our study as a reference, in clinical practice, clinicians will be able to conduct a more targeted genetic consultation for different kinds of PGT patients.

Oocyte Degeneration After ICSI Is Not an Indicator of Live Birth in Young Women

INTRODUCTION

Intracytoplasmic sperm injection (ICSI) was introduced in 1990s as one of the most dramatic breakthroughs in assisted reproductive technology. Even with advances in ICSI technology, this mechanical micromanipulation carries a 5 to 19% risk of oocyte degeneration. Whether the presence of oocyte degeneration reflects the sibling oocyte quality and predicts the sibling embryo development potential and clinical pregnancy outcomes remains controversial. There is no study showing the competence of the sibling embryos from the prospective of cumulative live birth rate. Whether oocyte degeneration is associated with poor quality of the remainder of the cohort remains further to be elucidated.

METHOD

This retrospective observational study included a total of 488 OPU cycles underwent ICSI with fresh cleavage stage embryo transfer and successive frozen/thawed embryo transfer (FET) cycles from January 2018 to December 2019. All female patients were under the age of 35 years, and underwent ICSI with or without oocyte degeneration (OD). Cycles with at least one oocyte degenerated were defined as oocyte degeneration group (OD group), and cycles with no oocyte degenerated were defined as non-OD group. The OD group was further divided to three subgroups according to different oocyte degeneration rate (<10%, 10-20%, and >20%).

RESULTS

There were no significant differences with regards to implantation rate (38.5% vs 35.1%, P=0.302), clinical pregnancy rate (54.9% vs 50.3%, P=0.340), and LBR per OPU cycle (47.0% vs 42.9%, P=0.395) between OD and non-OD groups. Initial gonadotropin dosage, E₂ level on hCG day and the number of matured oocytes appeared to be independent risk factors for OD. The adjusted odds ratio of live birth rate per OPU cycle were similar in different oocyte degeneration rate subgroups. The ongoing pregnancy/LBR per transfer in FET cycles was not significantly different between OD group and non-OD groups (38.8% vs 43.9%, P=0.439). The cumulative LBR per OPU cycle was also comparable between OD and non-OD group (63.4% vs 64.8%, P=0.760).

CONCLUSION

The results provide cycle-based evidence that the presence of oocyte degeneration after ICSI is not an indicator for predicting the cumulative live birth rate per OPU cycle in young women.

Eleven healthy live births: a result of simultaneous preimplantation genetic testing of α- and β-double thalassemia and aneuploidy screening

PURPOSE

To evaluate the efficacy of preimplantation genetic testing (PGT) for α- and β-double thalassemia combined with aneuploidy screening using next-generation sequencing (NGS).

METHODS

An NGS-based PGT protocol was performed between 2017 and 2018 for twelve couples, each of which carried both α- and β-thalassemia mutations. Trophectoderm biopsy samples underwent whole-genome amplification using multiple displacement amplification (MDA), followed by NGS for thalassemia detection and aneuploidy screening. A selection of several informative single nucleotide polymorphisms (SNPs) established haplotypes. Aneuploidy screening was performed only on unaffected noncarriers and carriers. Unaffected and euploid embryos were transferred into the uterus through frozen-thawed embryo transfer (FET).

RESULTS

A total of 280 oocytes were retrieved following 18 ovum pick-up (OPU) cycles, with 182 normally fertilized and 112 cultured to become blastocysts. One hundred and seven (95.5%, 107/112) blastocysts received conclusive PGT results, showing 56 (52.3%, 56/107) were unaffected. Thirty-seven (66.1%, 37/56) of the unaffected were also identified as euploid. One family had no transferable embryos. Unaffected and euploid embryos were then transferred into the uterus of the other 11 couples resulting in 11 healthy live births. The clinical pregnancy rate was 61.1% (11/18) per OPU and 68.8% (11/16) per FET, with no miscarriage reported. Seven families accepted the prenatal diagnosis and received consistent results with the NGS-based PGT.

CONCLUSION

This study indicated that NGS could realize the simultaneous PGT of double thalassemia and aneuploidy screening in a reliable and accurate manner. Moreover, it eliminated the need for multiple biopsies, alleviating the potential damages to the pre-implanted blastocysts.

Outcomes of Preimplantation Genetic Testing for Single Gene Defects in a Privately Funded Period and Publicly Funded Period: A North-American Single Center Experience

BACKGROUND

The purpose of this study was to assess whether the outcomes from IVF-preimplantation genetic testing (IVF-PGT) cycles for single gene defects (SGD) (PGT-M) differ between a privately funded period (PRP) and publicly funded period (PUP).

METHODS

A retrospective cohort study was conducted in a North-American single tertiary center. The PRP (March 1998 to July 2010) comprised 56 PGT-M cycles from 58 IVF cycles in 38 couples, and the PUP (August 2010 to May 2015) comprised 59 PGT-M cycles from 87 IVF cycles in 38 couples. One PGT-M cycle is defined as one biopsy procedure from one or serial IVF cycles. A p-value of 0.05 was considered statistically significant.

RESULTS

The clinical pregnancy rates (CPR) per PGT-M cycle were 30.4% and 52.5% in each period, respectively (p=0.021). The live birth rates (LBR) per PGT-M cycle were 21.5% versus 40.9% in each period, respectively (p=0.037). A sub-analysis within the PUP comparing 39 PGT-M cycles from 39 IVF cycles with 20 PGT-M cycles from 49 IVF cycles yielded CPRs per PGT-M cycle of 64.1% and 30.0% and LBRs per PGT-M cycle of 53.8% and 15.0%, in each group, respectively (p< 0.05 for both).

CONCLUSION

The transition from private to public funding and a single embryo transfer (ET) guideline has little impact on embryological and clinical outcomes of PGT-M cycles, and results in lower rates of multiple pregnancies. However, these two systems may serve different populations.

Embryo pooling: a promising strategy for managing insufficient number of embryos in preimplantation genetic diagnosis

This retrospective study evaluated the embryo pooling strategy for managing insufficient number of embryos in preimplantation genetic diagnosis (PGD) through serial vitrification of cleavage-stage embryos from consecutive cycles, and simultaneous blastocysts biopsy in combination with blastocysts obtained in ultimate fresh cycle. A retrospective analysis of the cumulative pregnancy rate of 68 patients underwent cleavage-stage embryos accumulation (Embryo Pooling Group) and 94 patients underwent one stimulation cycle (Control Group) over a 2-year period were conducted. The blastocyst formation rate was comparable between the consecutive cycles and the ultimate cycle in embryo pooling group (56.0 versus 62.0%, p = .078). No significant difference existed between twice-vitrified and once-vitrified warmed blastocysts with respect to implantation rate (50.8 versus 46.3%, p = .658). The implantation rate and cumulative pregnancy rate of embryo pooling group were 49.0 and 67.6%, respectively, which were statistically comparable to the corresponding values of 48.9 and 73.4% obtained in control group. Our study suggests that in patients undergoing ICSI-PGD who do not reach enough embryos in a single stimulation cycle, pooling embryos from consecutive ovarian stimulation cycles is a promising strategy, which can render a cumulative pregnancy rate comparable to those patients who only require one stimulation cycle.

Preimplantation and prenatal diagnosis, wrongful birth and wrongful life: a global view of bioethical and legal controversies

BACKGROUND

Prenatal diagnosis based on different technologies is increasingly used in developed countries and has become a common strategy in obstetric practice. The tests are crucial in enabling mothers to make informed decisions about the possibility of terminating pregnancy. They have generated numerous bioethical and legal controversies in the field of 'wrongful life' claims (action brought by or on behalf of a child against the mother or other people, claiming that he or she has to endure a not-worth-living existence) and 'wrongful birth' claims (action brought by the mother or parents against the physician for being burdened with an unwanted, often disabled child, which could have been avoided).

OBJECTIVE AND RATIONALE

The possibility which exists nowadays to intervene actively by programming and deciding the phases linked to procreation and birth has raised several questions worldwide. The mother's right to self-determination could be an end but whether or not this right is absolute is debatable. Freedom could, with time, act as a barrier that obstructs intrusion into other people's lives and their personal choices. Therapeutic choices may be manageable in a liberal sense, and the sanctity of life can be inflected in a secular sense. These sensitive issues and the various points of view to be considered have motivated this review.

SEARCH METHODS

Literature searches were conducted on relevant demographic, social science and medical science databases (SocINDEX, Econlit, PopLine, Medline, Embase and Current Contents) and via other sources. Searches focused on subjects related to bioethical and legal controversies in the field of preimplantation and prenatal diagnosis, wrongful birth and wrongful life. A review of the international state of law was carried out, focusing attention on the peculiar issue of wrongful life and investigating the different jurisdictional solutions of wrongful life claims in a comparative survey.

OUTCOMES

Courts around the world are generally reluctant to acknowledge wrongful life claims due to their ethical and legal implications, such as existence as an injury, the right not to be born, the nature of the harm suffered and non-existence as an alternative to a disabled life. Most countries have rejected such actions while at the same time approving those for wrongful birth. Some countries, such as France with a law passed in March 2002, have definitively excluded Wrongful Life action. Only in the Netherlands and in three states of the USA (California, Washington and New Jersey) Wrongful Life actions are allowed. In other countries, such as Belgium, legislation is unclear because, despite a first decision of the Court allowing Wrongful Life action, the case is still in progress. There is a complete lack of case law regarding wrongful conception, wrongful birth and wrongful life in a few countries, such as Estonia.

WIDER IMPLICATIONS

The themes of 'wrongful birth' and 'wrongful life' are charged with perplexing ethical dilemmas and raise delicate legal questions. These have met, in various countries and on certain occasions, with different solutions and have triggered ethical and juridical debate. The damage case scenarios result from a lack of information or diagnosis prior to the birth, which deprives the mother of the chance to terminate the pregnancy.

New Perspectives on Criteria for the Determination of HCG Trigger Timing in GnRH Antagonist Cycles

The aim of this study was to investigate 2 quantification criteria to evaluate the developmental condition of follicles cohort and clarify their impacts upon the determining of human chorionic gonadotropin trigger timing and the reproductive outcome: the proportion of mature follicles in growing follicles cohort on the day of human chorionic gonadotropin trigger and the peak estradiol level per oocyte on the day of human chorionic gonadotropin administration.Of the patients who underwent in vitro fertilization/ intracytoplasmic sperm injection-embryo transfer from 2011 to 2013, 492 controlled ovarian hyperstimulation cycles using gonadotropin-releasing hormone antagonists reaching the ovum pick-up and fresh embryo-transfer stage were included. Patients were divided into 3 groups according to their ≥17 mm/≥10 mm follicles ratio on the day of human chorionic gonadotropin administration (Low proportion: ≤30%, Middle proportion: 30%-60%, High proportion: ≥60%). Patients were divided into 5 groups according to their peak estradiol level/oocyte (Group A: <100 pg/mL per oocyte, Group B: 100-199 pg/mL per oocyte, Group C: 200-299 pg/mL per oocyte, Group D: 300-399 pg/mL per oocyte, Group E ≥400 pg/mL per oocyte) as well. Comparison among groups was made regarding ovarian stimulation characteristics, fertilization rate, good quality embryo rate, implantation, pregnancy, and live birth rates.On the basis of ≥17 mm/≥10 mm follicles ratio, the number of oocyte retrieved in low proportion group is more than other 2 groups. Implantation rate, clinical pregnancy, and live birth rate in high proportion group were 25.8%, 42.7%, and 31.1%, respectively, which is highest in 3 groups, and statistical significance existed between high and middle proportion groups. When the division is based on peak estradiol level/oocyte, the number of oocyte retrieved of ≥400 pg/mL per oocyte Group was significantly lowest compared with the other 4 groups. Matured ovum rate, fertilization rate, and good quality embryos rate exhibited an increasing trend as the peak estradiol level/oocyte increased. While pregnancy rate, implantation rate, and live birth rate were found to be lower whenever estradiol/oocyte ratio exceeded 400 pg/mL per oocyte or less than 100 pg/mL per oocyte, and there is statistical difference.Patients with the proportion of mature follicle reaching 60% on the day of human chorionic gonadotropin trigger and peak estradiol/oocyte level within 100∼399 pg/mL range can get a better pregnancy and implantation rate.