Case report: Preimplantation genetic testing for infantile GM1 gangliosidosis

Ganglioside-monosialic acid (GM1) gangliosidosis (ICD-10: E75.1; OMIM: 230500, 230600, 230650) is a rare autosomal recessive hereditary disease, lysosomal storage disorder caused by mutations in the GLB1 gene that lead to the absence or insufficiency of β-galactosidase. In this study, we report a case of a Russian family with a history of GM1 gangliosidosis. The family had a child who, from the age of 6 months, experienced a gradual loss of developmental skills, marked by muscle flaccidity, psychomotor retardation, hepatosplenomegaly, and the onset of tonic seizures by the age of 8 months. Funduscopic examination revealed a «cherry red spot» in the macula, which is crucial for the diagnosis of lipid storage disorders. To find the pathogenic variants responsible for these clinical symptoms, the next-generation sequencing approach was used. The analysis revealed two variants in the heterozygous state: a frameshift variant c.699delG (rs1452318343, ClinVar ID 928700) in exon 6 and a missense variant c.809A>C (rs371546950, ClinVar ID 198727) in exon 8 of the GLB1 gene. The spouses were advised to plan the pregnancy with assisted reproductive technology (ART), followed by preimplantation genetic testing for monogenic disorder (PGT-M) on the embryos. Trophectoderm biopsy was performed on 8 out of 10 resulting embryos at the blastocyst stage. To perform PGT-M, we developed a novel testing system, allowing for direct analysis of disease-causing mutations, as well as haplotype analysis based on the study of polymorphic markers-short tandem repeats (STR), located upstream and downstream of the GLB1 gene. The results showed that four embryos were heterozygous carriers of pathogenic variants in the GLB1 gene (#1, 2, 5, 8). Two embryos had a compound heterozygous genotype (#3, 4), while the embryos #7 and 9 did not carry disease-causing alleles of the GLB1 gene. The embryo #7 without pathogenic variants was transferred after consideration of its morphology and growth rate. Prenatal diagnosis in the first trimester showed the absence of the variants analyzed in the GLB1 gene in the fetus. The pregnancy resulted in the delivery of a female infant who did not inherit the disease-causing variants in the GLB1 gene.

First preimplantation genetic testing case of Meckel syndrome with a novel homozygous TXNDC15 variant in a non-consanguineous Chinese family

BACKGROUND

Meckel-Gruber syndrome (MKS) is a perinatally lethal, genetically heterogeneous, autosomal recessive condition caused by defective primary cilium formation. So far, the association of TXNDC15-related MKS has been reported in only five independent families from diverse ethnic origins, including Saudi, Pakistani, Estonian, and Indian. Here, we report a fetus diagnosed with MKS at 12 weeks, exhibiting typical ultrasound findings.

METHODS

Low-coverage whole-genome sequencing was used to identify chromosomal abnormalities. Trio-base whole exome sequencing (trio-WES) was performed to investigate the potential pathogenic variants associated with MKS. Preimplantation genetic testing for monogenic disorders (PGT-M) was applied to prevent the transmission of the pathogenic variant.

RESULTS

A novel homozygous pathogenic variant in the TXNDC15 gene was identified through trio-WES. The application of PGT-M successfully prevented the transmission of the pathogenic variant and resulted in an ongoing pregnancy.

CONCLUSION

This is the first report of a TXNDC15 variant in the Chinese population and the first PGT case of TXNDC15-related MKS worldwide. The successful application of PGT-M in this family provides a potential approach for other monogenic diseases. Our case expands the variant spectrum of TXNDC15 and contributes to the molecular diagnosis and genetic counseling for MKS. This case underscores the importance of appropriate genetic testing methods and accurate genetic counseling in the diagnosis of rare monogenic diseases.

Genetic counseling for pre-implantation genetic testing of monogenic disorders (PGT-M)

Pre-implantation genetic testing (PGT) is a vital tool in preventing chromosomal aneuploidies and other genetic disorders including those that are monogenic in origin. It is performed on embryos created by intracytoplasmic sperm injection (ICSI). Genetic counseling in the area of assisted reproductive technology (ART) has also evolved along with PGT and is considered an essential and integral part of Reproductive Medicine. While PGT has the potential to prevent future progeny from being affected by genetic conditions, genetic counseling helps couples understand and adapt to the medical, psychological, familial and social implications of the genetic contribution to disease. Genetic counseling is particularly helpful for couples with recurrent miscarriages, advanced maternal age, a partner with a chromosome translocation or inversion, those in a consanguineous marriage, and those using donor gametes. Partners with a family history of genetic conditions including hereditary cancer, late onset neurological diseases and with a carrier status for monogenic disorders can benefit from genetic counseling when undergoing PGT for monogenic disorders (PGT-M). Genetic counseling for PGT is useful in cases of Mendelian disorders, autosomal dominant and recessive conditions and sex chromosome linked disorders and for the purposes of utilizing HLA matching technology for creating a savior sibling. It also helps in understanding the importance of PGT in cases of variants of uncertain significance (VUS) and variable penetrance. The possibilities and limitations are discussed in detail during the sessions of genetic counseling.

Public Awareness and Acceptability of PGT-M in Cancer Predisposition Syndromes

Cancer Predisposition Syndromes (CPSs), also known as Hereditary Cancer Syndromes (HCSs), represent a group of genetic disorders associated with an increased lifetime risk of developing cancer. In this article, we provide an overview of the reproductive options for patients diagnosed with CPS, focusing on the emerging role of Preimplantation Genetic Testing for Monogenic disorders (PGT-M). Specifically, we conducted a literature review about the awareness and acceptability of its application to CPSs. Based on the available data, the awareness of the applicability of PGT-M for CPSs appears to be limited among both patients and physicians, and a heterogeneous set of factors seems to influence the acceptability of the procedure. Our findings highlight the need for increasing education about the use of PGT-M for CPSs. In this context, guidelines developed by professional or institutional bodies would represent a useful reference tool to assist healthcare professionals in providing proper preconception counseling.

PGT-M, a Useful Tool to Manage the Lynch Syndrome Transmission

Lynch syndrome is one of the most common hereditary cancer sensitivity syndromes and is caused by autosomal-dominant germline mutations in DNA mismatch repair genes. In patients affected by this syndrome, pre-implantation genetic testing for monogenic disorders (PGT-M) could be the elective technique used to prevent the transmission of this hereditary syndrome to offspring. Notably, despite the severity of the condition, some authors have observed a markedly lower demand for PGT-M in these patients compared to those with other hereditary conditions. A 34-year-old woman with a medical history of Lynch syndrome associated with endometrial cancer came to the Villa Mafalda fertility center in Rome in order to conceive a healthy baby. In a pre-implantation genetic testing for aneuploidy (PGT-A) + PGT-M cycle, eight blastocysts were formed. Six out of eight blastocysts were affected by the same mother syndrome. One of the other two was aneuploid and the other one was a mosaic embryo, which resulted in a healthy pregnancy. The aim of this report is to emphasize the importance of a multidisciplinary approach to managing patients with this condition. In vitro fertilization (IVF), specifically PGT-M, is a tool that allow patients to conceive biological children with lower risk of inheriting the disease.

Integrated treatment guided by RNA-seq-based endometrial receptivity assessment for infertility complicated by MEN1

Background

Preimplantation genetic testing (PGT) serves as a tool to avoid genetic disorders in patients with known genetic conditions. However, once a selected embryo is transferred, implantation success is attained independent of embryo quality. Using PGT alone is unable to tackle implantation failure caused by endometrial receptivity (ER) abnormalities in these patients.

Methods

We validated our newly developed RNA-seq-based ER test (rsERT) in a retrospective cohort study including 511 PGT cycles and reported experience in treating an infertile female patient complicated by multiple endocrine neoplasia type 1 (MEN1).

Results

Significant improvement in the clinical pregnancy rate was found in the performed personalized embryo transfer (pET) group (CR, 69.7%; P = 0.035). In the rare MEN1 case, pET was done according to the prediction of the optimal time of window of implantation after unaffected blastocysts were obtained by PGT-M, which ultimately led to a healthy live birth. However, none of the mRNA variants identified in the patient showed a strong association with the MEN1 gene.

Conclusions

Applying the new rsERT along with PGT improved ART outcomes and brought awareness of the importance of the ER examination in MEN1 infertile female patients. MEN1-induced endocrine disorder rather than MEN1 mutation contributes to the ER abnormality.

Trial Registration

Reproductive Medicine Ethics Committee of Xiangya Hospital Registry No.: 2022010.

A long-read sequencing and SNP haplotype-based novel preimplantation genetic testing method for female ADPKD patient with de novo PKD1 mutation

The autosomal dominant form of polycystic kidney disease (ADPKD) is the most common hereditary disease that causes late-onset renal cyst development and end-stage renal disease. Preimplantation genetic testing for monogenic disease (PGT-M) has emerged as an effective strategy to prevent pathogenic mutation transmission rely on SNP linkage analysis between pedigree members. Yet, it remains challenging to establish reliable PGT-M methods for ADPKD cases or other monogenic diseases with de novo mutations or without a family history. Here we reported the application of long-read sequencing for direct haplotyping in a female patient with de novo PKD1 c.11,526 G > C mutation and successfully established the high-risk haplotype. Together with targeted short-read sequencing of SNPs for the couple and embryos, the carrier status for embryos was identified. A healthy baby was born without the PKD1 pathogenic mutation. Our PGT-M strategy based on long-read sequencing for direct haplotyping combined with targeted SNP haplotype can be widely applied to other monogenic disease carriers with de novo mutation.

Preimplantation genetic testing for sickle cell disease: a cost-effectiveness analysis

Objective

To evaluate the cost-effectiveness of in vitro fertilization with preimplantation genetic testing for monogenic disease (IVF + PGT-M) in the conception of a nonsickle cell disease (non-SCD) individual compared with standard of care treatment for a naturally conceived, sickle cell disease (SCD)-affected individual.

Design

A Markov simulation model was constructed to evaluate a one-time IVF + PGT-M treatment compared with the lifetime standard of care costs of treatment for an individual potentially born with SCD. Using an annual discount rate of 3% for cost and outcome measures, quality-adjusted life years were constructed from utility weights and life expectancy values and then used as the effectiveness measurement. An incremental cost-effectiveness ratio was calculated for both treatment arms, and a willingness-to-pay threshold of $50,000 per quality-adjusted life year was assumed.

Setting

Tertiary care or university medical center.

Patients

A hypothetical cohort of 10,000 patients was analzyed over a lifetime horizon using yearly cycles.

Interventions

In vitro fertilization with preimplantation genetic testing for monogenic disease use in conception of a non-SCD individual.

Main Outcome Measures

The primary outcomes of interest were the incremental cost and effectiveness of an IVF+PGT-M conception compared with the SOC treatment of an SCD-affected individual.

Results

In vitro fertilization with preimplantation genetic testing for monogenic disease was the optimal strategy in 93.17% of the iterations. An incremental savings of $137,594 was demonstrated with a gain of 1.96 QALYs and 3.69 life years over a lifetime. Sensitivity analysis demonstrated that SOC treatment never met equivalent cost-effectiveness.

Conclusions

Our model demonstrates that IVF + PGT-M for selection against SCD, compared with lifetime SOC treatment for those affected, is the most cost-effective strategy within the United States healthcare sector.

Fertility Preservation as an Option for Women with Genetic Disorders: Insights from a SWOT Analysis on Elective Oocyte Freezing and Preimplantation Genetic Testing

This paper uses a SWOT (strengths, weaknesses, opportunities, and threats) analysis to overview the option of fertility preservation in women with genetic diseases, who would later use preimplantation genetic testing for monogenic disorders, in order to not transmit their condition. Strengths associated with elective oocyte freezing are ethical considerations, overall maternal and fetal safety, and effectiveness, if performed at <35 years of age. Weaknesses are related to costs and rare but present (<1-3%) risks of maternal complications. Counselling on fertility management aimed at preventing infertility offers a valuable opportunity, the same as it has been in oncological patients' care. The potentially high percentage of women with genetic conditions who would return to use their frozen oocytes also represents an opportunity together with the minimization of the need for egg donation, which has higher obstetrical risks compared to the use of autologous oocytes. Finally, a threat is represented by the potential psychological distress to young women who could never attempt to become pregnant through preimplantation genetic testing, or do it before any decline in their fertility. Potential unknown future long-term health risks for children conceived after egg vitrification/thawing are also a threat, but current knowledge is reassuring. Altogether, early counselling on the option of fertility preservation should thus be incorporated into standard care of all patients with any genetic condition.

Preimplantation genetic testing for Aicardi-Goutières syndrome induced by novel compound heterozygous mutations of TREX1: an unaffected live birth

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a rare, autosomal recessive, hereditary neurodegenerative disorder. It is characterized mainly by early onset progressive encephalopathy, concomitant with an increase in interferon-α levels in the cerebrospinal fluid. Preimplantation genetic testing (PGT) is a procedure that could be used to choose unaffected embryos for transfer after analysis of biopsied cells, which prevents at-risk couples from facing the risk of pregnancy termination.

METHODS

Trio-based whole exome sequencing, karyotyping and chromosomal microarray analysis were used to determine the pathogenic mutations for the family. To block the inheritance of the disease, multiple annealing and looping-based amplification cycles was used for whole genome amplification of the biopsied trophectoderm cells. Sanger sequencing and next-generation sequencing (NGS)-based single nucleotide polymorphism (SNP) haplotyping were used to detect the state of the gene mutations. Copy number variation (CNV) analysis was also carried out to prevent embryonic chromosomal abnormalities. Prenatal diagnosis was preformed to verify the PGT outcomes.

RESULTS

A novel compound heterozygous mutation in TREX1 gene was found in the proband causing AGS. A total of 3 blastocysts formed after intracytoplasmic sperm injection were biopsied. After genetic analyses, an embryo harbored a heterozygous mutation in TREX1 and without CNV was transferred. A healthy baby was born at 38th weeks and prenatal diagnosis results confirmed the accuracy of PGT.

CONCLUSIONS

In this study, we identified two novel pathogenic mutations in TREX1, which has not been previously reported. Our study extends the mutation spectrum of TREX1 gene and contributes to the molecular diagnosis as well as genetic counseling for AGS. Our results demonstrated that combining NGS-based SNP haplotyping for PGT-M with invasive prenatal diagnosis is an effective approach to block the transmission of AGS and could be applied to prevent other monogenic diseases.

Ovarian endometrioma increases the embryo aneuploid rate: an analysis of 7092 biopsied blastocysts from fertile monogenetic disease carriers

BACKGROUND

Endometriosis affects many reproductive aged patients with fertility decline and poor outcomes of assisted reproductive treatments, mainly by decreased ovarian reserve and lower fertilization and implantation rates. In recent decade, altered oocyte microenvironments and abnormal spindle organization have been reported to be critical to oocyte chromosomal segregation, organization and aneuploid formation. However, clinical evidences are still limited on whether endometriosis influences oocyte and embryo development. We aimed to figure out the impact of endometrioma on embryo aneuploid formation.

METHOD

This retrospective cohort study included 1,021 patients (7,092 biopsied embryos) from January 2012 to December 2020. Fertile patients without a history of miscarriage who underwent PGT-M treatment with aneuploid screening were included. Patients with ovarian endometrioma were defined as the study group, while patients without endometriosis were defined as the control group. All demographic, controlled ovarian stimulation treatment and aneuploid screening data were recorded and compared.

RESULTS

The incidence of endometrioma in our study population was 6.5%. There were 7,092 embryos biopsied in total, with 308 embryos in the study group and 6,784 embryos in the control groups. The demographic characteristics were comparable between the two groups except the basal FSH level (6.02 IU/L vs. 5.52 IU/L, p = 0.012). The euploid rate of the study group was significantly lower than that of the control group (52.6% vs. 61.8%, p = 0.012), while the oocyte maturation, fertilization, usable embryo and blastocyst formation rates were comparable. Adjusted for basal FSH level, starting stimulating gonadotropin dosage, total gonadotropin dosage and FSH level on hCG day, euploid rate was still negatively related to endometrioma status.

CONCLUSIONS

Endometrioma status disturbs oocyte and embryo development. For infertile patients with endometrioma who require assisted reproductive treatment, pre-treatment is necessary to improve treatment outcomes.

TRIAL REGISTRATION

Not applicable.

Identification of carrier status of Xp22.31 microdeletions associated with X-linked ichthyosis at the single-cell level using haplotype linkage analysis by karyomapping

PURPOSE

Currently, owing to the limitations of high-throughput sequencing depth and the allele dropout caused by the whole-genome amplification, detection of chromosomal variants in embryos with CNVs <5 Mb is unsatisfactory at the single-cell level using only conventional sequencing methods. Therefore, here we aimed to use a strategy of preimplantation genetic testing for monogenic (PGT-M) to compensate for the shortcomings of conventional sequencing methods. The purpose of this study is to report the effectiveness of haplotype linkage analysis by karyomapping for preimplantation diagnosis microdeletion diseases.

METHODS

Six couples carrying chromosomal microdeletions associated with X-linked ichthyosis were recruited, and all couples entered the PGT process. Multiple displacement amplification (MDA) method was used to amplify the whole-genome DNA of trophectoderm cells. Then karyomapping based on single nucleotide polymorphism (SNP) was used for haplotype linkage analysis to detect alleles carrying microdeletions, and CNVs of embryos were identified to determine euploid identity. Amniotic fluid tests were performed in the second trimester to verify the PGT-M results.

RESULTS

All couples were tested for chromosomal microdeletions, with deletion fragments ranging in size from 1.60 to 1.73 Mb, and one partner in each couple did not carry the microdeletion. Three couples successfully underwent PGT-M assisted conception and obtained healthy live births.

CONCLUSION

This study shows that haplotype linkage analysis by karyomapping could effectively detect the carrier status of embryos with microdeletions at the single-cell level. This approach may be applied to the preimplantation diagnosis of various chromosomal microvariation diseases.

The correlation between morphological parameters and the incidence of de novo chromosomal abnormalities in 3238 biopsied blastocysts

PURPOSE

The aim of this study was to determine the relationship between morphological parameters and the incidence of de novo chromosomal abnormalities.

METHODS

This was a retrospective cohort study of 652 patients who underwent 921 cycles with 3238 blastocysts biopsied. The embryo grades were evaluated according to Gardner and Schoolcraft's system. The incidence of euploidy, whole chromosomal aneuploidy (W-aneuploidy), segmental chromosomal aneuploidy (S-aneuploidy), and mosaicism in trophectoderm (TE) cell biopsies was analyzed.

RESULTS

The euploidy decreased significantly with maternal age and was positively correlated biopsy day and morphological parameters. The W-aneuploidy increased significantly with maternal age and was negatively correlated biopsy day and morphological parameters. Parental age, TE biopsy day, and morphological parameters were not associated with S-aneuploidy and mosaicism, except that TE grade C blastocysts had significantly higher mosaicism than TE grade A blastocysts. Subanalysis in different female age groups showed that euploidy and W-aneuploidy had a significant correlation with TE biopsy day among women aged ≤ 30 y and 31-35 y, with expansion degree among women aged ≥ 36 y, with ICM grade among women aged ≥ 31 y, and with TE grade among all female age ranges.

CONCLUSION

Female age, embryo developmental speed and blastocyst morphological parameters are associated with euploidy and whole chromosomal aneuploidy. The predictive value of these factors varies across female age groups. Parental age, embryo developmental speed, expansion degree, and ICM grade are not associated with the incidence of segmental aneuploidy or mosaicism, but TE grade seemingly has a weak correlation with segmental aneuploidy and mosaicism in embryos.

The association between a carrier state of FMR1 premutation and numeric sex chromosome variations

PURPOSE

Women carriers of FMR1 premutation are at increased risk of early ovarian dysfunction and even premature ovarian insufficiency. The aim of this study was to examine a possible association between FMR1 permutation and numeric sex chromosome variations.

METHODS

A retrospective case-control study conducted in the reproductive center of a university-affiliated medical center. The primary outcome measure was the rate of sex chromosomal numerical aberrations, as demonstrated by haplotype analyses, in FMR1 premutation carriers compared to X-linked preimplantation genetic testing for monogenic/single gene defect (PGT-M) cycles for other indications that do not affect the ovarian follicles and oocytes.

RESULTS

A total of 2790 embryos with a final genetic analysis from 577 IVF PGT-M cycles were included in the final analysis. Mean age was similar between the groups, however, FMR1 carriers required more gonadotropins, and more women were poor responders with three or less oocytes collected. The ratio of embryos carrying a numeric sex chromosome variation was similar: 8.3% (138/1668) of embryos in the FMR1 group compared to 7.1% (80/1122) in the controls. A subgroup analysis based on age and response to stimulation has not demonstrated a significant difference either.

CONCLUSIONS

Although carriers of FMR1 premutation exhibit signs of reduced ovarian response, it does not seem to affect the rate of numeric sex chromosomal variation compared to women undergoing PGT-M for other indications. This suggests that the mechanism for chromosomal number aberrations in women at advanced maternal age are different to those FMR1 premutation carriers with poor ovarian reserve.

Embryo Selection for a Carrier of an Early-Onset Alzheimer's Disease-Associated Mutation in the PSEN1 Gene

Alzheimer's disease (AD) is the most common neurodegenerative dementia. It manifests as early-onset or late-onset AD. Early-onset AD represents about 5.5% of the total cases and occurs in patients under age 65. The EOAD progresses more aggressively and has a shorter life expectancy due to a greater pathogenic load. We present two asymptomatic siblings, a 30-year-old male and a 34- year-old female, who are heterozygous carriers of a pathogenic variant c.428T>C (Ile143Thr) in the presenilin 1 (PSEN1) gene. During genetic counseling, assisted reproduction techniques (ART) coupled with embryo biopsy and a preimplantation genetic test for monogenic disorders (PGT-M) were recommended to provide reproductive care for the patients and their partners. ART and preimplantation genetic testing (PGT) have made it possible to have chromosomally normal and genetically unaffected offspring, allowing patients with genetic diseases to become parents.

Thin endometrial lining: is it more prevalent in patients utilizing preimplantation genetic testing for monogenic disease (PGT-M) and related to prior hormonal contraceptive use?

STUDY QUESTION

Is a thin endometrial lining before ovulation triggering more prevalent in patients utilizing preimplantation genetic testing for monogenic disease (PGT-M) compared to the regular IVF/ICSI population and is this associated with prior hormonal contraceptive use?

SUMMARY ANSWER

Thin (<8 mm) endometrial lining is more prevalent in PGT-M patients compared to the regular IVF/ICSI population and is associated with both longer prior hormonal contraceptive use and a shorter cessation interval of hormonal contraceptives before IVF/ICSI treatment.

WHAT IS KNOWN ALREADY

Thin endometrial lining has been associated with lower pregnancy rates in IVF/ICSI cycles and increased chances of miscarriage and low birth weight. Endometrial thinning and atrophy occur during hormonal contraceptive use. Patients utilizing PGT-M typically use hormonal contraceptives up until treatment to avoid the risk of conception of a genetically affected child. Whether this could negatively affect endometrial thickness achieved during subsequent IVF/ICSI cycles is not known.

STUDY DESIGN, SIZE, DURATION

A retrospective case control study was performed, including all PGT-M patients attending the University Medical Centre Groningen (cases), between 2009 and 2018. The control group consisted of two non-PGT IVF/ICSI patients for each PGT-M patient, matched for age and treatment period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

First cycles of 122 PGT-M patients and 240 controls were included. Cessation interval of hormonal contraceptives was categorized as late cessation (cessation <1 year prior to treatment) or early cessation (>1 year prior to treatment). Endometrial thickness was routinely measured on the day of hCG triggering or 1 day prior. The prevalence of an endometrial lining <8 mm was compared between PGT-M patients and controls. Hormonal contraceptive use (both duration and cessation interval) was compared between both groups. Univariable and multivariable regression analyses were performed to identify risk factors for thin endometrial lining. In addition, cycle and pregnancy outcomes were compared within control/PGT-M groups between patients with endometrial lining > or <8 mm.

MAIN RESULTS AND THE ROLE OF CHANCE

Thin endometrial lining on the day of hCG triggering was found significantly more often in the PGT-M group, compared to controls: 32% vs 11% (mean difference 21.0%, 95% CI: 11.7, 30.3%). As expected, more patients in the PGT-M group ceased their hormonal contraception late (<1 year): 64% vs 2% in the control group (mean difference 61.9%, 95% CI: 53.0, 70.8%). Average duration of hormonal contraceptive use was 10.6 years in the PGT-M group vs 9.3 years in controls (mean difference 1.3 years, 95% CI: 0.2, 2.3 years). Multivariable logistic regression analysis identified late cessation (OR: 6.0, 95% CI: 1.9-19.2) and duration of prior hormonal contraceptive use (OR per year increase 1.1, 95% CI: 1.0-1.2) as significant independent risk factors for a thin endometrial lining. In relation to outcome, we found a statistically significant increase in miscarriage rate in PGT-M patients with an endometrial lining <8 mm compared to those with an endometrial lining >8 mm (20.0% vs 1.7%, mean difference 18.3%, 95% CI: 2.3, 34.3%). A trend towards lower birth weight and gestation- and gender-adjusted birth weight (z-score) was also found in this group. No statistically significant differences were detected in pregnancy rate, live birth rate, or incidence of preterm delivery or SGA. Within the control group, no statistically significant differences were found in outcomes between patients with an endometrial lining <8 compared to an endometrial lining >8 mm.

LIMITATIONS, REASONS FOR CAUTION

The study is retrospective. Various types of hormonal contraceptives were reported which possibly exert different effects on the endometrial lining. In relation to pregnancy outcome measures, numbers were very limited; therefore, no firm conclusions should be drawn.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides further insight into the role of prior hormonal contraceptive use as a possible contributor to the occurrence of thin endometrial lining during ART treatment. Future studies should provide more information on its clinical relevance, to determine whether PGT-M patients can be reassured, or should be counselled to stop hormonal contraceptive use and change to an alternative contraceptive method prior to PGT treatment.

STUDY FUNDING/COMPETING INTERESTS

No specific funding was used and no conflicts of interests are declared.

TRIAL REGISTRATION NUMBER

N/A.

Combining PGT-A with PGT-M risks trying to do too much

The primary objective of preimplantation genetic testing for monogenic disorders (PGT-M) is to avoid having a child with a serious monogenic disease. Combining testing for unrelated sporadic chromosomal abnormalities (PGT-A) and excluding embryos with chromosomally abnormal results from transfer proffers the chance to mitigate the risk of miscarriage and to reduce the number of embryo transfers, but also risks excluding healthy embryos from transfer due to abnormal test results that do not reflect the true potential of the embryo. The theoretical utility of combining PGT-M with PGT-A is explored in this communication. It is concluded that PGT-M without PGT-A is preferred to achieve an unaffected live birth. Since PGT-M is mostly undertaken by couples where the female partner is younger than 35 years, PGT-A is likely to marginally mitigate the risk of miscarriage. Experimental non-selection studies are needed to assess the potential detrimental effect of combining PGT-M with PGT-A in a clinical setting.

A review of normative documents on preimplantation genetic testing: Recommendations for PGT-P

PURPOSE

Recently, preimplantation genetic testing (PGT) for polygenic conditions (PGT-P) has been introduced commercially. In view of the lack of specific guidance on this development, we analyzed normative documents on PGT for monogenic conditions (PGT-M) to understand what we can learn from these documents for recommendations for PGT-P.

METHODS

We conducted a systematic review of normative guidelines and recommendations on PGT-M. The aim was to understand what the current consensus and disagreements are on ethical acceptability of PGT-M and how this compares with PGT-P.

RESULTS

We analyzed 38 documents by advisory committees at the national, European, and global level. In total, 2 themes were identified, which included the following: (1) what PGT is considered appropriate for and (2) who can make decisions regarding the use of PGT. Many aspects of PGT-M documents apply to PGT-P as well. Additional factors such as the fact that PGT-P screens for risk indications of multiple polygenic conditions increase ethical difficulties regarding severity, risk, autonomy, and informed decision-making.

CONCLUSION

On the basis of PGT-M normative documents, we conclude that ethical acceptability for PGT-P is limited. Our findings present various factors that have to be considered for the development of guidelines and the appropriateness of PGT.

Hemoglobinopathies and preimplantation diagnostics

Hemoglobinopathies constitute some of the most common inherited disorders worldwide. Manifestations are very severe, patient management is difficult and treatment is not easily accessible. Preimplantation genetic testing for monogenic disorders (PGT-M) is a valuable reproductive option for hemoglobinopathy carrier-couples as it precludes the initiation of an affected pregnancy. PGT-M is performed on embryos generated by assisted reproductive technologies and only those found to be free of the monogenic disorder are transferred to the uterus. PGT-M has been applied for 30 years now and β-thalassemia is one of the most common indications. PGT may also be applied for human leukocyte antigen typing to identify embryos that are unaffected and also compatible with an affected sibling in need of hemopoietic stem cell transplantation. PGT-M protocols have evolved from PCR amplification-based, where a small number of loci were analysed, to whole genome amplification-based, the latter increasing diagnostic accuracy, enabling the development of more generic strategies and facilitating multiple diagnoses in one embryo. Currently, numerous PGT-M cycles are performed for the simultaneous diagnosis of hemoglobinopathies and screening for chromosomal abnormalities in the embryo in an attempt to further improve success rates and increase deliveries of unaffected babies.

Genetic of preimplantation diagnosis of dysmorphic facial features and intellectual developmental disorder (CHDFIDD) without congenital heart defects

Background

Cyclin‐dependent kinase 13 plays a critical role in the regulation of gene transcription. Recent evidence suggests that heterozygous variants in CDK13 are associated with a syndromic form of mental deficiency and developmental delay, which is inherited in an autosomal dominant manner.

Methods

A mentally retarded mother (33‐year‐old) and son (10‐year‐old boy) in our hospital with CDK13 variant (c.2149 (exon 4) G>A. p.Gly717Arg) were detected by whole‐exome sequencing (WES). All published CDK13 variant syndrome cases as of November 11, 2021, were searched, and their clinical information was recorded and summarized.

Results

We studied two patients in a Chinese family with a heterozygous constitutional CDK13 variant (c.2149 (exon 4) G>A. p.Gly717Arg), exhibiting the classical characteristics of dysmorphic facial features and intellectual developmental disorder (CHDFIDD, OMIM # 617360), without congenital heart defects. This is the first reported case of an adult patient with a CDK13 variant that gave birth to the next generation with the same variant. Preimplantation genetic testing for monogenic disease (PGT‐M) was performed for the proband and her husband with full informed consent and successfully blocked the inheritance of the disease.

Conclusion

Our study is of great significance for molecular diagnosis and genetic counseling of patients with CDHFIDD and extends the variant spectrum of CDK13.

A systematic review of the views of healthcare professionals on the scope of preimplantation genetic testing

Preimplantation genetic testing (PGT) involves testing embryos created through in vitro fertilization for the presence of hereditary genetic disorders and chromosome abnormalities. PGT for monogenic conditions (PGT-M) is generally performed for childhood-onset, lethal disorders, but is increasingly accepted for certain adult-onset conditions, conditions with available treatment options or conditions with lower penetrance. Furthermore, the development of PGT for polygenic conditions (PGT-P) makes ethical questions regarding PGT indications imperative. A systematic review was therefore performed to gather and analyse studies on the perspectives of healthcare professionals on the appropriate scope of PGT, with the aim of getting insights into the concerns about the scope of PGT now and in the near future. PRISMA guidelines were followed. Twelve qualitative articles were included. The main themes extracted were the scope of PGT and decision-making about PGT. Defining 'a serious genetic condition' was seen as complex, but severity, high penetrance and absence of treatability and patients' experience were seen as relevant indications to determine the appropriateness of PGT. In navigating the decision-making processes with patients, professionals experienced friction between setting limits and respecting patients' autonomy. Such friction and ethical dilemmas around seriousness, informed decision-making and preventative medicine show that while expanding the list of possible PGT indications and the development of PGT-P could augment patients' reproductive autonomy, it could also lead to an increased reproductive 'burden' for patients. These insights are crucial for establishing guidelines that help healthcare professionals navigate ethical tensions associated with PGT.

A novel EDA variant causing X-linked hypohidrotic ectodermal dysplasia: Case report

Hereditary ectodermal dysplasias are a complex group of inherited disorders characterised by abnormalities in two or more ectodermal derivatives (skin, nails, sweat glands, etc.). There are two main types of these disorders – hidrotic and hypohidrotic/anhidrotic ectodermal dysplasias. Hypohidrotic ectodermal dysplasia (HED) or Christ-Siemens-Touraine syndrome (OMIM: 305100) occurs in 1 out of 5000–10,000 births [19] and has an X-linked recessive inheritance pattern (X-linked hypohydrotic ectodermal dysplasia – XLHED) [2].

The main cause of XLHED is a broad range of pathogenic variants in the EDA gene (HGNC:3157, Xq12-13) which encodes the transmembrane protein ectodysplasin-A [4]. We report here the case of a patient with a novel inherited allelic variant in the EDA gene – NM_001399.5:c.337C>T (p.Gln113*) – in the heterozygous state. Targeted family member screening was conducted and other carriers of this EDA gene pathogenic variant were identified and phenotypically characterised. The patient subsequently underwent in vitro fertilisation with preimplantation genetic testing for monogenic diseases (PGT-M).

Cell-based non-invasive prenatal testing for monogenic disorders: confirmation of unaffected fetuses following preimplantation genetic testing

PURPOSE

Proof of concept of the use of cell-based non-invasive prenatal testing (cbNIPT) as an alternative to chorionic villus sampling (CVS) following preimplantation genetic testing for monogenic disorders (PGT-M).

METHOD

PGT-M was performed by combined testing of short tandem repeat (STR) markers and direct mutation detection, followed by transfer of an unaffected embryo. Patients who opted for follow-up of PGT-M by CVS had blood sampled, from which potential fetal extravillous throphoblast cells were isolated. The cell origin and mutational status were determined by combined testing of STR markers and direct mutation detection using the same setup as during PGT. The cbNIPT results with respect to the mutational status were compared to those of genetic testing of the CVS.

RESULTS

Eight patients had blood collected between gestational weeks 10 and 13, from which 33 potential fetal cell samples were isolated. Twenty-seven out of 33 isolated cell samples were successfully tested (82%), of which 24 were of fetal origin (89%). This corresponds to a median of 2.5 successfully tested fetal cell samples per case (range 1-6). All fetal cell samples had a genetic profile identical to that of the transferred embryo confirming a pregnancy with an unaffected fetus, in accordance with the CVS results.

CONCLUSION

These findings show that although measures are needed to enhance the test success rate and the number of cells identified, cbNIPT is a promising alternative to CVS.

TRIAL REGISTRATION NUMBER

N-20180001.

Clinical validity and utility of preconception expanded carrier screening for the management of reproductive genetic risk in IVF and general population

STUDY QUESTION

What is the clinical validity and utility of preconception Expanded Carrier Screening (ECS) application on the management of prospective parents?

SUMMARY ANSWER

The high detection rate of at-risk couples (ARCs) and the high proportion opting for IVF/preimplantation genetic testing (PGT) treatment demonstrate the clinical utility of ECS in the preconception space in IVF and general population.

WHAT IS KNOWN ALREADY

About 2-4% of couples are at risk of conceiving a child with an autosomal recessive or X-linked genetic disorder. In recent years, the increasing cost-effectiveness of genetic diagnostic techniques has allowed the creation of ECS panels for the simultaneous detection of multiple recessive disorders. Comprehensive preconception genetic screening holds the potential to significantly improve couple's genetic risk assessment and reproductive planning to avoid detectable inheritable genetic offspring.

STUDY DESIGN, SIZE, DURATION

A total of 3877 individuals without a family history of genetic conditions were analyzed between January 2017 and January 2020. Of the enrolled individuals, 1212 were gamete donors and 2665 were patients planning on conceiving from both the IVF and the natural conception group. From the non-donor cohort, 1133 were analyzed as individual patients, while the remaining ones were analyzed as couples, for a total of 766 couples.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A focused ECS panel was developed following American College of Obstetrics and Gynecology ACOG-recommended criteria (prevalence, carrier rate, severity), including highly penetrant severe childhood conditions. Couples were defined at-risk when both partners carried an autosomal recessive pathogenic/likely pathogenic variant (PLP) on the same gene or when the woman was a carrier of an X-linked PLP variant. ARC detection rate defined the clinical validity of the ECS approach. Clinical utility was evaluated by monitoring ARCs reproductive decision making.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 402 individuals (10.4%) showed PLP for at least one of the genes tested. Among the 766 couples tested, 173 showed one carrier partner (22.6%), whereas 20 couples (2.6%) were found to be at increased risk. Interestingly, one ARC was identified as a result of cascade testing in the extended family of an individual carrying a pathogenic variant on the Survival Of Motor Neuron 1SMN1 gene. Of the identified ARCs, 5 (0.7%) were at risk for cystic fibrosis, 5 (0.7%) for fragile X syndrome, 4 (0.5%) for spinal muscular atrophy, 4 (0.5%) for Beta-Thalassemia/Sickle Cell Anemia, 1 (0.1%) for Smith-Lemli-Opitz Syndrome and 1 (0.1%) for Duchenne/Becker Dystrophy. Fifteen ARCs were successfully followed up from both the IVF and the natural conception groups. All of these (15/15) modified their reproductive planning by undergoing ART with Preimplantation Genetic Testing for Monogenic disease and Aneuploidies (PGT-M and PGT-A). To date, 6/15 (40%) couples completed their PGT cycle with euploid/unaffected embryos achieving a pregnancy after embryo transfer and three of them have already had an unaffected baby.

LIMITATIONS, REASONS FOR CAUTION

The use of a limited panel of core gene-disease pairs represents a limitation on the research perspective as it can underestimate the rate of detectable carriers and ARCs in this cohort of prospective parents. Expanding the scope of ECS to a larger panel of conditions is becoming increasingly feasible, thanks to a persistent technological evolution and progressive cataloging of gene-disease associations.

WIDER IMPLICATIONS OF THE FINDINGS

These results highlight the potential clinical validity and utility of ECS in reducing the risk of a pregnancy affected by a detectable inheritable genetic condition. The steady reduction in the costs of genetic analyses enables the expansion of monogenic testing/screening applications at the preimplantation stage, thus, providing valid decisional support and reproductive autonomy to patients, particularly in the context of IVF.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. A.C., M.F., S.C., M.P., L.G., and C.P. are employees of Igenomix Italy. C.S. is the head of the scientific board of Igenomix.

TRIAL REGISTRATION NUMBER

N/A.

Comprehensive preimplantation genetic testing by massively parallel sequencing

STUDY QUESTION

Can whole genome sequencing (WGS) offer a relatively cost-effective approach for embryonic genome-wide haplotyping and preimplantation genetic testing (PGT) for monogenic disorders (PGT-M), aneuploidy (PGT-A) and structural rearrangements (PGT-SR)?

SUMMARY ANSWER

Reliable genome-wide haplotyping, PGT-M, PGT-A and PGT-SR could be performed by WGS with 10× depth of parental and 4× depth of embryonic sequencing data.

WHAT IS KNOWN ALREADY

Reduced representation genome sequencing with a genome-wide next-generation sequencing haplarithmisis-based solution has been verified as a generic approach for automated haplotyping and comprehensive PGT. Several low-depth massively parallel sequencing (MPS)-based methods for haplotyping and comprehensive PGT have been developed. However, an additional family member, such as a sibling, or a proband, is required for PGT-M haplotyping using low-depth MPS methods.

STUDY DESIGN, SIZE, DURATION

In this study, 10 families that had undergone traditional IVF-PGT and 53 embryos, including 13 embryos from two PGT-SR families and 40 embryos from eight PGT-M families, were included to evaluate a WGS-based method. There were 24 blastomeres and 29 blastocysts in total. All embryos were used for PGT-A. Karyomapping validated the WGS results. Clinical outcomes of the 10 families were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A blastomere or a few trophectoderm cells from the blastocyst were biopsied, and multiple displacement amplification (MDA) was performed. MDA DNA and bulk DNA of family members were used for library construction. Libraries were sequenced, and data analysis, including haplotype inheritance deduction for PGT-M and PGT-SR and read-count analysis for PGT-A, was performed using an in-house pipeline. Haplotyping with a proband and parent-only haplotyping without additional family members were performed to assess the WGS methodology. Concordance analysis between the WGS results and traditional PGT methods was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

For the 40 PGT-M and 53 PGT-A embryos, 100% concordance between the WGS and single-nucleotide polymorphism (SNP)-array results was observed, regardless of whether additional family members or a proband was included for PGT-M haplotyping. For the 13 embryos from the two PGT-SR families, the embryonic balanced translocation was detected and 100% concordance between WGS and MicroSeq with PCR-seq was demonstrated.

LIMITATIONS, REASONS FOR CAUTION

The number of samples in this study was limited. In some cases, the reference embryo for PGT-M or PGT-SR parent-only haplotyping was not available owing to failed direct genotyping.

WIDER IMPLICATIONS OF THE FINDINGS

WGS-based PGT-A, PGT-M and PGT-SR offered a comprehensive PGT approach for haplotyping without the requirement for additional family members. It provided an improved complementary method to PGT methodologies, such as low-depth MPS- and SNP array-based methods.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the research grant from the National Key R&D Program of China (2018YFC0910201 and 2018YFC1004900), the Guangdong province science and technology project of China (2019B020226001), the Shenzhen Birth Defect Screening Project Lab (JZF No. [2016] 750) and the Shenzhen Municipal Government of China (JCYJ20170412152854656). This work was also supported by the National Natural Science Foundation of China (81771638, 81901495 and 81971344), the National Key R&D Program of China (2018YFC1004901 and 2016YFC0905103), the Shanghai Sailing Program (18YF1424800), the Shanghai Municipal Commission of Science and Technology Program (15411964000) and the Shanghai 'Rising Stars of Medical Talent' Youth Development Program Clinical Laboratory Practitioners Program (201972). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

A comprehensive PGT-M strategy for ADPKD patients with de novo PKD1 mutations using affected embryo or gametes as proband

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease characterized by the development of renal cysts and progression to renal failure. Preimplantation genetic testing-monogenic disease (PGT-M) is an alternative option to obtain healthy babies. However, de novo PKD1 mutation of one of the spouses or the absence of a positive family history poses a serious challenge to PGT-M. Here, we described a comprehensive strategy which includes preimplantation genetic testing for aneuploidies (PGT-A) study and monogenic diagnosis study for ADPKD patients bearing de novo mutations. The innovation of our strategy is to use the gamete (polar body or single sperm) as proband for single-nucleotide polymorphism (SNP) linkage analysis to detect an embryo's carrier status. Nine ADPKD couples with either de novo mutation or without a positive family history were recruited and a total of 34 embryos from 13 PGT-M cycles were examined. Within these nine couples, two successfully delivered healthy babies had their genetic status confirmed by amniocentesis. This study provides a creative approach for embryo diagnosis of patients with de novo mutations or patients who lack essential family members for linkage analysis.

A novel monogenic preimplantation genetic testing strategy for sporadic polycystic kidney caused by de novo PKD1 mutation

Autosomal dominant hereditary polycystic kidney disease (ADPKD) is the most common inherited kidney disease that causes end-stage renal disease and kidney failure. Preimplantation genetic testing for monogenic (PGT-M) can effectively prevent the transmission of genetic diseases from parents to the offspring before pregnancy. However, PGT-M currently adopts the single nucleotide polymorphism (SNP) linkage analysis for embryo's pathogenic gene carrying status and linkage analysis requires proband of the family. Here we report a new PGT-M strategy using single sperm SNP linkage analysis for male patient with sporadic ADPKD caused by de novo PKD1 mutation. We recruited five couples with male patient with ADPKD caused by de novo PKD1 mutation, and 39 embryos from six PGT-M cycles were detected. The five couples had at least one embryo that does not carry the PKD1 mutation. Within these five couples, the accuracy of carrier status of embryos was confirmed by amniotic fluid gene detection of two couples and two couples successfully delivered healthy fetuses. Therefore, the new PGT-M strategy of using single sperm SNP linkage analysis was proved to be feasible and effective for male patient with ADPKD caused by de novo PKD1 mutation.

A Successful Case for Deselection of Albino Embryo and Live Birth of Albinism-Free Healthy Baby Followed by PGT-M

In recent years, Preimplantation genetic testing for monogenic disorders (PGT-M) has gained a lot of focus in the field of assisted reproduction technology, various studies have been published in support of it and many are opposing its role. It has been criticized due to many ethical as well as scientific reasons, but there is no doubt that PGT-M has been one of the most important breakthroughs in in vitro fertilization. A critical aspect of this technology is the possibility that the biopsy itself can adversely affect the quality of embryo and compulsion of embryo freezing. Oculocutaneous albinism (OCA) is a condition which is related to skin, hair, eye color (pigments), where affected individuals typically have very fair skin and white- or light-colored hair. These patients are prone to skin cancers on prolonged sun exposure. It also reduces the pigmentation of the colored part of the eyes (the iris) and the light-sensitive tissue at the back of the eye (the retina). People with this condition usually have problem in vision such as reduced sharpness, involuntary eye movements, and photophobia. Here, we report the successful use of PGT-M and a novel protocol for the preimplantation genetic diagnosis of OCA following trophectoderm cell biopsy from blastocysts and the birth of a healthy infant to a couple having previously affected child.

Timing day-3 vitrification for PGT-M embryos: pre- or post-blastomere biopsy?

PURPOSE

To assess the efficacy and clinical outcomes of preimplantation genetic testing for monogenic diseases (PGT-M), following blastomere biopsy prior or following vitrification.

METHODS

A cohort-historical study of all consecutive patients admitted to IVF in a large tertiary center for PGT-M and PCR cycle from September 2016 to March 2020. Patients were divided into 4 groups: Group A1 consisted of patients undergoing day-3 embryos biopsy followed by a fresh transfer of unaffected embryos. Group A2 consisted of Group A1 patients that their surplus unaffected embryos were vitrified, thawed, and transferred in a subsequent FET cycle. Group B1 consisted of patients that their day-3 embryos were vitrified intact (without biopsy) for a subsequent FET cycle. Later embryos were thawed and underwent blastomere biopsies, and the unaffected embryos were transferred, while the surplus unaffected embryos were re-vitrified for a subsequent FET cycle. Group B2 consisted of Group B1 patients that their surplus unaffected embryos were re-vitrified, thawed, and transferred in a subsequent FET cycle. The laboratory data and clinical results were collected and compared between groups.

RESULTS

A total of 368 patients underwent 529 PGT-M cycles in our center: 347 with day-3 embryos biopsied before undergoing vitrification (Group A1) and 182 following vitrification and thawing (Group B1). There were no between group differences in embryo survival rate post-thawing, nor the ongoing implantation and pregnancy rates.

CONCLUSION

In PGT-M cycles, the timing of embryos vitrification, whether prior or following blastomere biopsy, has no detrimental effect on post-thawing embryo survival rate, nor their potential ongoing implantation and pregnancy rates.

Preimplantation Genetic Testing of Multiple Endocrine Neoplasia Type 2A

Background: When discussing matters of reproduction, the 2015 revised guidelines for the management of medullary thyroid carcinoma recommend that patients diagnosed with multiple endocrine neoplasia type 2A (MEN 2A) are informed about the option of Preimplantation Genetic Testing for Monogenic Disorders (PGT-M). In addition, patients seem to have a genuine interest in reproductive options. However, there are just two reports worldwide of this technology being used for patients with MEN 2A. We here present, in a Danish couple where the man has MEN 2A, the first European family with children born after PGT-M. Objective: To report the results of PGT-M in relation to multiple endocrine neoplasia type 2A with the aim to increase awareness among physicians treating this and other genetic disorders. Methods: A Danish couple was referred to the PGT Center at Copenhagen University Hospital Rigshospitalet and opted for PGT-M after counseling by a clinical geneticist and a fertility doctor. The embryos were diagnosed using microsatellite polymorphic marker close to RET. Results: The couple had two healthy children born in 2017 and 2019 as a result of a total of three ICSI treatments including controlled ovarian stimulation, oocyte retrieval and PGT-M, and a total of six blastocyst transfers. Conclusion: A session with a clinical geneticist covering all reproductive options for patients in early adult life is a relevant part of the clinical management of patients with MEN 2A, and other patients with hereditary cancer predisposition syndromes.

Bayesian model for accurate MARSALA (mutated allele revealed by sequencing with aneuploidy and linkage analyses)

Purpose

This study is aimed at increasing the accuracy of preimplantation genetic test for monogenic defects (PGT-M).

Methods

We applied Bayesian statistics to optimize data analyses of the mutated allele revealed by sequencing with aneuploidy and linkage analyses (MARSALA) method for PGT-M. In doing so, we developed a Bayesian algorithm for linkage analyses incorporating PCR SNV detection with genome sequencing around the known mutation sites in order to determine quantitatively the probabilities of having the disease-carrying alleles from parents with monogenic diseases. Both recombination events and sequencing errors were taken into account in calculating the probability.

Results

Data of 28 in vitro fertilized embryos from three couples were retrieved from two published research articles by Yan et al. (Proc Natl Acad Sci. 112:15964–9, 2015) and Wilton et al. (Hum Reprod. 24:1221–8, 2009). We found the embryos deemed “normal” and selected for transfer in the previous publications were actually different in error probability of 10⁻⁴–4%. Notably, our Bayesian model reduced the error probability to 10⁻⁶–10⁻⁴%. Furthermore, a proband sample is no longer required by our new method, given a minimum of four embryos or sperm cells.

Conclusion

The error probability of PGT-M can be significantly reduced by using the Bayesian statistics approach, increasing the accuracy of selecting healthy embryos for transfer with or without a proband sample.

Electronic supplementary material

The online version of this article (10.1007/s10815-019-01451-8) contains supplementary material, which is available to authorized users.

Overview of Preimplantation Genetic Diagnosis (PGD): Historical Perspective and Future Direction

Preimplantation genetic diagnosis (PGD) can be considered the earliest form of prenatal testing. It was first used in humans over 26 years ago. At its inception, PGD could only be performed for a limited number of genetic disorders. Technological advances in molecular biology and cytogenomics have been utilized in the field of PGD to greatly expand the spectrum of genetic disorders that can now be detected in early human embryos.

The effect of repeated biopsy on pre-implantation genetic testing for monogenic diseases (PGT-M) treatment outcome

PURPOSE

To study the outcome of repeated biopsy for pre-implantation genetic testing in case of failed genetic diagnosis in the first biopsy.

METHODS

The study group included 81 cycles where embryos underwent re-biopsy because there were no transferable embryos after the first biopsy: in 55 cycles, the first procedure was polar body biopsy (PBs) and the second cleavage-stage (BB); in 26 cycles, the first was BB and the second trophectoderm (BLAST) biopsy. The control group included 77 cycles where embryos underwent successful genetic diagnosis following the first biopsy, matched by maternal age, egg number, genetic inheritance type, and embryonic stage at the first biopsy. We measured genetic diagnosis rate, clinical pregnancy rates (PRs), live-birth rates (LBRs), gestational age, and birth weight.

RESULTS

For repeated biopsy, genetic diagnosis was received in 67/81 cycles (82.7%); at a higher rate in PB + BB than in BB + BLAST (49/55, 89.1% and 18/26, 69.2% respectively, p = 0.055). Transferable embryos were found in 47 and 68 cycles in the study and the control groups. PRs/ET were 20/47 (42.6%) and 36/68 (52.9%) (p = 0.27), 16/36 (44.4%) following PB + BB, and 4/11 (36.4%) following BB + BLAST (p = 0.74). LBRs/ET were 13/47 (27.7%) in study group, and 28/68 (41.2%) in the controls (p = 0.14), 10/36 (27.8%) following PB + BB group, and 3/11 (27.3%) following BB + BLAST (p > 0.99). Gestational age and birth weight were similar in all groups.

CONCLUSIONS

Re-biopsy of embryos when no genetic diagnosis could be reached following the first biopsy, achieved high rates of genetic diagnosis, pregnancies, and live births.

Genetic counseling prior to Assisted Reproductive Technology procedures in the era of cytogenomics

The possibility of sequencing hundreds of genes simultaneously and performing molecular karyotyping thanks to the introduction of novel genetic tools has expanded the use of preconception screening for blastocyst recessive mutations and aneuploidies before embryo transfer, with the ultimate purpose of increasing the proportion of normal healthy newborns. Since medically-assisted reproduction procedures are increasingly required to be eugenic, and the aforementioned genetic tests cover only half of the potential genetic diseases occurring at birth, it seems reasonable to incorporate genetic counseling in the practice of assisted reproduction to avoid prosecution for malpractice.