Reproductive genetic counseling challenges associated with diagnostic exome sequencing in a large academic private reproductive genetic counseling practice

Impact of prenatal genomics on clinical genetics practice

Genetic testing for prenatal diagnosis in the pre-genomic era primarily focused on detecting common fetal aneuploidies, using methods that combine maternal factors and imaging findings. The genomic era, ushered in by the emergence of new technologies like chromosomal microarray analysis and next-generation sequencing, has transformed prenatal diagnosis. These new tools enable screening and testing for a broad spectrum of genetic conditions, from chromosomal to monogenic disorders, and significantly enhance diagnostic precision and efficacy. This chapter reviews the transition from traditional karyotyping to comprehensive sequencing-based genomic analyses. We discuss both the clinical utility and the challenges of integrating prenatal exome and genome sequencing into prenatal care and underscore the need for ethical frameworks, improved prenatal phenotypic characterization, and global collaboration to further advance the field.

Clinical features and genetic analysis of a case series of skeletal ciliopathies in a prenatal setting

BACKGROUND

Short-rib polydactyly syndrome (SRPS) refers to a group of lethal skeletal dysplasias that can be difficult to differentiate between subtypes or from other non-lethal skeletal dysplasias such as Ellis-van Creveld syndrome and Jeune syndrome in a prenatal setting. We report the ultrasound and genetic findings of four unrelated fetuses with skeletal dysplasias.

METHODS

Systemic prenatal ultrasound examination was performed in the second or third trimester. Genetic tests including GTG-banding, single nucleotide polymorphism (SNP) array and exome sequencing were performed with amniocytes or aborted fetal tissues.

RESULTS

The major and common ultrasound anomalies for the four unrelated fetuses included short long bones of the limbs and narrow thorax. No chromosomal abnormalities and pathogenic copy number variations were detected. Exome sequencing revealed three novel variants in the DYNC2H1 gene, namely NM_001080463.2:c.6809G > A p.(Arg2270Gln), NM_001080463.2:3133C > T p.(Gln1045Ter), and NM_001080463.2:c.337C > T p.(Arg113Trp); one novel variant in the IFT172 gene, NM_015662.3:4540-5 T > A; and one novel variant in the WDR19 gene, NM_025132.4:c.2596G > C p.(Gly866Arg). The genotypes of DYNC2H1, IFT172 and WDR19 and the phenotypes of the fetuses give hints for the diagnosis of short-rib thoracic dysplasia (SRTD) with or without polydactyly 3, 10, and 5, respectively.

CONCLUSION

Our findings expand the mutation spectrum of DYNC2H1, IFT172 and WDR19 associated with skeletal ciliopathies, and provide useful information for prenatal diagnosis and genetic counseling on rare skeletal disorders.

Uncovering the Genetic Basis of Congenital Heart Disease: Recent Advancements and Implications for Clinical Management

Congenital heart disease (CHD) is the most prevalent hereditary disorder, affecting approximately 1% of all live births. A reduction in morbidity and mortality has been achieved with advancements in surgical intervention, yet challenges in managing complications, extracardiac abnormalities, and comorbidities still exist. To address these, a more comprehensive understanding of the genetic basis underlying CHD is required to establish how certain variants are associated with the clinical outcomes. This will enable clinicians to provide personalized treatments by predicting the risk and prognosis, which might improve the therapeutic results and the patient's quality of life. We review how advancements in genome sequencing are changing our understanding of the genetic basis of CHD, discuss experimental approaches to determine the significance of novel variants, and identify barriers to use this knowledge in the clinics. Next-generation sequencing technologies are unravelling the role of oligogenic inheritance, epigenetic modification, genetic mosaicism, and noncoding variants in controlling the expression of candidate CHD-associated genes. However, clinical risk prediction based on these factors remains challenging. Therefore, studies involving human-induced pluripotent stem cells and single-cell sequencing help create preclinical frameworks for determining the significance of novel genetic variants. Clinicians should be aware of the benefits and implications of the responsible use of genomics. To facilitate and accelerate the clinical integration of these novel technologies, clinicians should actively engage in the latest scientific and technical developments to provide better, more personalized management plans for patients.

Access to prenatal exome sequencing for fetal malformations: A qualitative landscape analysis in the US

OBJECTIVE

There is increasing evidence supporting the clinical utility of next generation sequencing for identifying fetal genetic disorders. However, there are limited data on the demand for and accessibility of these tests, as well as payer coverage in the prenatal context. We sought to identify clinician perspectives on the utility of prenatal exome sequencing (ES) and on equitable access to genomic technologies for the care of pregnancies complicated by fetal structural anomalies.

METHOD

We conducted two focus group discussions and six interviews with a total of 13 clinicians (11 genetic counselors; 2 Maternal Fetal Medicine/Geneticists) from U.S. academic centers and community clinics.

RESULTS

Participants strongly supported ES for prenatal diagnostic testing in pregnancies with fetal structural anomalies. Participants emphasized the value of prenatal ES as an opportunity for a continuum of care before, during, and after a pregnancy, not solely as informing decisions about abortions. Cost and coverage of the test was the main access barrier, and research was the main pathway to access ES in academic centers.

CONCLUSION

Further integrating the perspectives of additional key stakeholders are important for understanding clinical utility, developing policies and practices to address access barriers, and assuring equitable provision of prenatal diagnostic testing.

Challenges and Pragmatic Solutions in Pre-Test and Post-Test Genetic Counseling for Prenatal Exome Sequencing

The yield of genetic prenatal diagnosis has been notably improved by introducing whole genome chromosomal microarray (CMA) and prenatal exome sequencing (pES). However, together with increased numbers of diagnoses made, the need to manage challenging findings such as variants of unknown significance (VUS) and incidental findings (IF) also increased. We have summarized the current guidelines and recommendations and we have shown current solutions used in our tertiary center in the Netherlands. We discuss four of the most common clinical situations: fetus with normal pES results, fetus with a pathogenic finding explaining the fetal phenotype, fetus with a variant of uncertain clinical significance fitting the phenotype and fetus with a variant leading to an incidental diagnosis. Additionally, we reflect on solutions in order to facilitate genetic counseling in an NGS-era.

A novel non-sense variant in the OFD1 gene caused Joubert syndrome

Background: Joubert syndrome (JBS) is a rare neurodevelopmental disorder associated with progressive renal, liver, and retinal involvement that exhibits heterogeneity in both clinical manifestations and genetic etiology. Therefore, it is difficult to make a definite prenatal diagnosis. Methods: Whole-exome sequencing and Sanger sequencing were performed to screen the causative gene variants in a suspected JBS family. RNA-seq and protein model prediction were performed to clarify the potential pathogenic mechanism. A more comprehensive review of previously reported cases with OFD1 variants is presented and may help to establish a genotype-phenotype. Results: We identified a novel non-sense variant in the OFD1 gene, OFD1 (NM_003611.3): c.2848A>T (p.Lys950Ter). Sanger sequencing confirmed cosegregation among this family. RNA-seq confirmed that partial degradation of mutant transcripts, which was predicted to be caused by the non-sense-mediated mRNA decay (NMD) mechanism, may explain the reduction in the proportion of mutant transcripts. Protein structure prediction of the non-sense variant transcript revealed that this variant may lead to a change in the OFD1 protein structure. Conclusion: The genetic variation spectrum of JBS10 caused by OFD1 was broadened. The novel variants further deepened our insight into the molecular mechanism of the disease.

Parental Hopes and Understandings of the Value of Prenatal Diagnostic Genomic Sequencing: A Qualitative Analysis

Objective: To provide qualitative empirical data on parental expectations of diagnostic prenatal genomic sequencing and the value of the results to families.

Methods: We interviewed 15 families—mothers and/or fathers—who had had prenatal genomic sequencing about their expectations and their respective evaluations of the benefits of genomic sequencing.

Results: Families’ hopes for genetic sequencing clustered around three themes: hoping to identify the cause of the fetal anomaly in a terminated pregnancy; hopes for guidance as to the likely outcome of current pregnancy; and hopes for information to support future family planning. In addition, hopes were discussed in terms of the potential for results to be beneficial in acquiring greater knowledge, while at the same time recognizing that new knowledge may raise more questions. Assessment of the value of sequencing largely mirrored these expectations when positive results seen. Negative results can also be seen as valuable in ruling out a genetic cause and in providing certainty that families had done everything that they could to know about the cause of fetal demise.

Conclusion: It would appear that with guidance from genetic counsellors, families were largely able to navigate the many uncertainties of prenatal genomic sequencing and thus see themselves as benefitting from sequencing. However, support structures are essential to guide them through their expectations and interpretations of results to minimize possible harms. Engaging in the process of genomic sequencing was seen as beneficial in of itself to families who would otherwise be left without any options to seek diagnostic answers.

OFD1: One gene, several disorders

The OFD1 protein is necessary for the formation of primary cilia and left–right asymmetry establishment but additional functions have also been ascribed to this multitask protein. When mutated, this protein results in a variety of phenotypes ranging from multiorgan involvement, such as OFD type I (OFDI) and Joubert syndromes (JBS10), and Primary ciliary dyskinesia (PCD), to the engagement of single tissues such as in the case of retinitis pigmentosa (RP23). The inheritance pattern of these condition differs from X‐linked dominant male‐lethal (OFDI) to X‐linked recessive (JBS10, PCD, and RP23). Distinctive biological peculiarities of the protein, which can contribute to explain the extreme clinical variability and the genetic mechanisms underlying the different disorders are discussed. The extensive spectrum of clinical manifestations observed in OFD1‐mutated patients represents a paradigmatic example of the complexity of genetic diseases. The elucidation of the mechanisms underlying this complexity will expand our comprehension of inherited disorders and will improve the clinical management of patients.

Molecular Approaches in Fetal Malformations, Dynamic Anomalies and Soft Markers: Diagnostic Rates and Challenges-Systematic Review of the Literature and Meta-Analysis

Fetal malformations occur in 2-3% of pregnancies. They require invasive procedures for cytogenetics and molecular testing. "Structural anomalies" include non-transient anatomic alterations. "Soft markers" are often transient minor ultrasound findings. Anomalies not fitting these definitions are categorized as "dynamic". This meta-analysis aims to evaluate the diagnostic yield and the rates of variants of uncertain significance (VUSs) in fetuses undergoing molecular testing (chromosomal microarray (CMA), exome sequencing (ES), genome sequencing (WGS)) due to ultrasound findings. The CMA diagnostic yield was 2.15% in single soft markers (vs. 0.79% baseline risk), 3.44% in multiple soft markers, 3.66% in single structural anomalies and 8.57% in multiple structural anomalies. Rates for specific subcategories vary significantly. ES showed a diagnostic rate of 19.47%, reaching 27.47% in multiple structural anomalies. WGS data did not allow meta-analysis. In fetal structural anomalies, CMA is a first-tier test, but should be integrated with karyotype and parental segregations. In this class of fetuses, ES presents a very high incremental yield, with a significant VUSs burden, so we encourage its use in selected cases. Soft markers present heterogeneous CMA results from each other, some of them with risks comparable to structural anomalies, and would benefit from molecular analysis. The diagnostic rate of multiple soft markers poses a solid indication to CMA.

Fetal hydrops and the Incremental yield of Next-generation sequencing over standard prenatal Diagnostic testing (FIND) study: prospective cohort study and meta-analysis

OBJECTIVE

To determine the incremental yield of exome sequencing (ES) over chromosomal microarray analysis (CMA) or karyotyping in prenatally diagnosed non-immune hydrops fetalis (NIHF).

METHODS

A prospective cohort study (comprising an extended group of the Prenatal Assessment of Genomes and Exomes (PAGE) study) was performed which included 28 cases of prenatally diagnosed NIHF undergoing trio ES following negative CMA or karyotyping. These cases were combined with data from a systematic review of the literature. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases were searched electronically (January 2000 to October 2020) for studies reporting on the incremental yield of ES over CMA or karyotyping in fetuses with prenatally detected NIHF. Inclusion criteria for the systematic review were: (i) at least two cases of NIHF undergoing sequencing; (ii) testing initiated based on prenatal ultrasound-based phenotype; and (iii) negative CMA or karyotyping result. The incremental diagnostic yield of ES was assessed in: (i) all cases of NIHF; (ii) isolated NIHF; (iii) NIHF associated with an additional fetal structural anomaly; and (iv) NIHF according to severity (i.e. two vs three or more cavities affected).

RESULTS

In the extended PAGE study cohort, the additional diagnostic yield of ES over CMA or karyotyping was 25.0% (7/28) in all NIHF cases, 21.4% (3/14) in those with isolated NIHF and 28.6% (4/14) in those with non-isolated NIHF. In the meta-analysis, the pooled incremental yield based on 21 studies (306 cases) was 29% (95% CI, 24-34%; P < 0.00001; I²  = 0%) in all NIHF, 21% (95% CI, 13-30%; P < 0.00001; I²  = 0%) in isolated NIHF and 39% (95% CI, 30-49%; P < 0.00001; I²  = 1%) in NIHF associated with an additional fetal structural anomaly. In the latter group, congenital limb contractures were the most prevalent additional structural anomaly associated with a causative pathogenic variant, occurring in 17.3% (19/110) of cases. The incremental yield did not differ significantly according to hydrops severity. The most common genetic disorders identified were RASopathies, occurring in 30.3% (27/89) of cases with a causative pathogenic variant, most frequently due to a PTPN11 variant (44.4%; 12/27). The predominant inheritance pattern in causative pathogenic variants was autosomal dominant in monoallelic disease genes (57.3%; 51/89), with most being de novo (86.3%; 44/51).

CONCLUSIONS

Use of prenatal next-generation sequencing in both isolated and non-isolated NIHF should be considered in the development of clinical pathways. Given the wide range of potential syndromic diagnoses and heterogeneity in the prenatal phenotype of NIHF, exome or whole-genome sequencing may prove to be a more appropriate testing approach than a targeted gene panel testing strategy. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Comprehensive evaluation of genetic variants using chromosomal microarray analysis and exome sequencing in fetuses with congenital heart defect

OBJECTIVE

To evaluate comprehensively, using chromosomal microarray analysis (CMA) and exome sequencing (ES), the prevalence of chromosomal abnormalities and sequence variants in unselected fetuses with congenital heart defect (CHD) and to evaluate the potential diagnostic yields of CMA and ES for different CHD subgroups.

METHODS

This was a study of 360 unselected singleton fetuses with CHD detected by echocardiography, referred to our department for genetic testing between February 2018 and December 2019. We performed CMA, as a routine test for aneuploidy and copy number variations (CNV), and then, in cases without aneuploidy or pathogenic CNV on CMA, we performed ES.

RESULTS

Overall, positive genetic diagnoses were made in 84 (23.3%) fetuses: chromosomal abnormalities were detected by CMA in 60 (16.7%) and sequence variants were detected by ES in a further 24 (6.7%) cases. The detection rate of pathogenic and likely pathogenic genetic variants in fetuses with non-isolated CHD (32/83, 38.6%) was significantly higher than that in fetuses with isolated CHD (52/277, 18.8%) (P < 0.001), this difference being due mainly to the difference in frequency of aneuploidy between the two groups. The prevalence of a genetic defect was highest in fetuses with an atrioventricular septal defect (36.8%), ventricular septal defect with or without atrial septal defect (28.4%), conotruncal defect (22.2%) or right ventricular outflow tract obstruction (20.0%). We also identified two novel missense mutations (c.2447G>C, p.Arg816Pro; c.1171C>T, p.Arg391Cys) and a new phenotype caused by variants in PLD1.

CONCLUSIONS

Chromosomal abnormalities were identified in 16.7% and sequence variants in a further 6.7% of fetuses with CHD. ES should be offered to all pregnant women with a CHD fetus without chromosomal abnormality or pathogenic CNV identified by CMA, regardless of whether the CHD is isolated. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Out-of-pocket and private pay in clinical genetic testing: A scoping review

Full coverage of the cost of clinical genetic testing is not always available through public or private insurance programs, or a public healthcare system. Consequently, some patients may be faced with the decision of whether to finance testing out-of-pocket (OOP), meet OOP expenses required by their insurer, or not proceed with testing. A scoping review was conducted to identify literature associated with patient OOP and private pay in clinical genetic testing. Seven databases (EMBASE, MEDLINE, CINAHL, PsychINFO, PAIS, the Cochrane Database of Systematic Reviews, and the JBI Evidence-Based Practice database) were searched, resulting in 83 unique publications included in the review. The presented evidence includes a descriptive analysis, followed by a narrative account of the extracted data. Results were divided into four groups according to clinical indication: (1) hereditary breast and ovarian cancer, (2) other hereditary cancers, (3) prenatal testing, (4) other clinical indications. The majority of studies focused on hereditary cancer and prenatal genetic testing. Overall trends indicated that OOP costs have fallen and payer coverage has improved, but OOP expenses continue to present a barrier to patients who do not qualify for full coverage.

Utilization and uptake of clinical genetics services in high-income countries: A scoping review

Ongoing rapid growth in the need for genetic services has the potential to severely strain the capacity of the clinical genetics workforce to deliver this care. Unfortunately, assessments of the scale of this health policy challenge and potential solutions are hampered by the lack of a consolidated evidence base on the growth in genetic service utilization. To enable health policy research and strategic planning by health systems in this area, we conducted a scoping review of the literature on the utilization and uptake of clinical genetics services in high-income countries published between 2010 and 2018. One-hundred-and-ninety-five unique studies were included in the review. Most focused on cancer (85/195; 44%) and prenatal care (50/195; 26%), which are consistently the two areas with the greatest volume of genetic service utilization in both the United States and other high-income countries. Utilization and uptake rates varied considerably and were influenced by contextual factors including health system characteristics, provider knowledge, and patient preferences. Moreover, growth in genetic service utilization appears to be driven to a significant degree by technological advances and the integration of new tests into clinical care. Our review highlights both the policy challenge posed by the rapid growth in the utilization of genetic services and the variability in this trend across clinical indications and health systems.

Prenatal Exome Sequencing: Background, Current Practice and Future Perspectives-A Systematic Review

The introduction of Next Generation Sequencing (NGS) technologies has exerted a significant impact on prenatal diagnosis. Prenatal Exome Sequencing (pES) is performed with increasing frequency in fetuses with structural anomalies and negative chromosomal analysis. The actual diagnostic value varies extensively, and the role of incidental/secondary or inconclusive findings and negative results has not been fully ascertained. We performed a systematic literature review to evaluate the diagnostic yield, as well as inconclusive and negative-result rates of pES. Papers were divided in two groups. The former includes fetuses presenting structural anomalies, regardless the involved organ; the latter focuses on specific class anomalies. Available findings on non-informative or negative results were gathered as well. In the first group, the weighted average diagnostic yield resulted 19%, and inconclusive finding rate 12%. In the second group, the percentages were extremely variable due to differences in sample sizes and inclusion criteria, which constitute major determinants of pES efficiency. Diagnostic pES availability and its application have a pivotal role in prenatal diagnosis, though more homogeneity in access criteria and a consensus on clinical management of controversial information management is envisageable to reach widespread use in the near future.

Beyond diagnostic yield: prenatal exome sequencing results in maternal, neonatal, and familial clinical management changes

Purpose

Previous studies have reported that prenatal exome sequencing (pES) can detect monogenic diseases in fetuses with congenital anomalies with diagnostic yields ranging from 6% to 81%, but there are few reports of its clinical utility.

Methods

We conducted a retrospective chart review of patients who had pES to determine whether results led to clinical management changes.

Results

Of 20 patients, 8 (40%) received a definitive diagnosis. Seven patients (35%) had medical management changes based on the pES results, including alterations to their delivery plan and neonatal management (such as use of targeted medications, subspecialty referrals, additional imaging and/or procedures). All patients who received a definitive diagnosis and one who received a likely pathogenic variant (n = 9; 45%) received specific counseling about recurrence risk and the medical/developmental prognosis for the baby. In five (25%) cases, the result facilitated a diagnosis in parents and/or siblings.

Conclusion

pES results can have significant impacts on clinical management, some of which would not be possible if testing is deferred until after birth. To maximize the clinical utility, pES should be prioritized in cases where multiple care options are available and the imaging findings alone are not sufficient to guide parental decision-making, or where postnatal testing will not be feasible.

COngenital heart disease and the Diagnostic yield with Exome sequencing (CODE) study: prospective cohort study and systematic review

OBJECTIVE

To determine the incremental yield of antenatal exome sequencing (ES) over chromosomal microarray analysis (CMA) or conventional karyotyping in prenatally diagnosed congenital heart disease (CHD).

METHODS

A prospective cohort study of 197 trios undergoing ES following CMA or karyotyping owing to CHD identified prenatally and a systematic review of the literature were performed. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov (January 2000 to October 2019) databases were searched electronically for studies reporting on the diagnostic yield of ES in prenatally diagnosed CHD. Selected studies included those with more than three cases, with initiation of testing based upon prenatal phenotype only and that included cases in which CMA or karyotyping was negative. The incremental diagnostic yield of ES was assessed in: (1) all cases of CHD; (2) isolated CHD; (3) CHD associated with extracardiac anomaly (ECA); and (4) CHD according to phenotypic subgroup.

RESULTS

In our cohort, ES had an additional diagnostic yield in all CHD, isolated CHD and CHD associated with ECA of 12.7% (25/197), 11.5% (14/122) and 14.7% (11/75), respectively (P = 0.81). The corresponding pooled incremental yields from 18 studies (encompassing 636 CHD cases) included in the systematic review were 21% (95% CI, 15-27%), 11% (95% CI, 7-15%) and 37% (95% CI, 18-56%), respectively. The results did not differ significantly when subanalysis was limited to studies including more than 20 cases, except for CHD associated with ECA, in which the incremental yield was greater (49% (95% CI, 17-80%)). In cases of CHD associated with ECA in the primary analysis, the most common extracardiac anomalies associated with a pathogenic variant were those affecting the genitourinary system (23/52 (44.2%)). The greatest incremental yield was in cardiac shunt lesions (41% (95% CI, 19-63%)), followed by right-sided lesions (26% (95% CI, 9-43%)). In the majority (68/96 (70.8%)) of instances, pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease genes. The most common (19/96 (19.8%)) monogenic syndrome identified was Kabuki syndrome.

CONCLUSIONS

There is an apparent incremental yield of prenatal ES in CHD. While the greatest yield is in CHD associated with ECA, consideration could also be given to performing ES in the presence of an isolated cardiac abnormality. A policy of routine application of ES would require the adoption of robust bioinformatic, clinical and ethical pathways. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Exploring the predicted yield of prenatal testing by evaluating a postnatal population with structural abnormalities using a novel mathematical model

OBJECTIVE

To determine the yield of prenatal testing and screening options after identification of fetal structural abnormalities using a novel mathematical model.

METHOD

A retrospective chart review was conducted to collect structural abnormality and genetic testing data on infants who were evaluated postnatally by a medical geneticist. A novel mathematical model was used to determine and compare the predicted diagnostic yields of prenatal testing and screening options.

RESULTS

Over a quarter of patients with at least one structural abnormality (28.1%, n = 222) had a genetic aberration identified that explained their phenotype. Chromosomal microarray (CMA) had the highest predicted diagnostic yield (26.8%, P < .001). Karyotype (20.8%) had similar yields as genome wide NIPT (21.2%, P = .859) and NIPT with select copy number variants (CNVs) (17.9%, P = .184). Among individuals with an isolated structural abnormality, whole exome sequencing (25.9%) and CMA (14.9%) had the highest predicted yields.

CONCLUSION

This study introduces a novel mathematical model for predicting the potential yield of prenatal testing and screening options. This study provides further evidence that CMA has the highest predicted diagnostic yield in cases with structural abnormalities. Screening with expanded NIPT options shows potential for patients who decline invasive testing, but only in the setting of adequate pre-test counseling.

Application of exome sequencing for prenatal diagnosis: a rapid scoping review

Genetic diagnosis provides important information for prenatal decision-making and management. Promising results from exome sequencing (ES) for genetic diagnosis in fetuses with structural anomalies are emerging. The objective of this scoping review was to identify what is known about the use of ES for genetic testing in prenatal cases with known or suspected genetic disease. A rapid scoping review was conducted over a six-week timeframe of English-language peer-reviewed studies. Search strategies for major databases (e.g., Medline) and gray literature were developed, and peer reviewed by information specialists. Identified studies were categorized and charted using tables and diagrams. Twenty-four publications were included from seven countries published between 2014 and 2019. Most commonly reported outcomes were diagnostic yields, which varied widely from 5% to 57%, and prenatal phenotype. Few studies reported clinical outcomes related to impact, decision-making, and clinical utility. Qualitative studies (n = 6) provided useful insights into patient and health-care provider experiences with ES. Findings suggest prenatal ES is beneficial, but more research is needed to better understand the clinical utility, circumstances for ideal use, feasibility, and costs of offering rapid ES as a routine option for prenatal genetic testing.

Considerations for whole exome sequencing unique to prenatal care

Whole exome sequencing (WES) is increasingly being used in the prenatal setting. The emerging data support the clinical utility of prenatal WES based on its diagnostic yield, which can be as high as 80% for certain ultrasound findings. However, detailed practice and laboratory guidelines, addressing the indications for prenatal WES and the surrounding technical, interpretation, ethical, and counseling issues, are still lacking. Herein, we review the literature and summarize the most recent findings and applications of prenatal WES. This review offers specialists and clinical genetic laboratorians a body of evidence and expert opinions that can serve as a resource to assist in their practice. Finally, we highlight the emerging technologies that promise a future of prenatal WES without the risks associated with invasive testing.

Next-Generation Sequencing Using a Cardiac Gene Panel in Prenatally Diagnosed Cardiac Anomalies

OBJECTIVE

Most prenatally identified congenital heart defects (CHDs) are the sole structural anomaly detected; however, there is a subgroup of cases where the specific genetic cause will impact prognosis, including chromosome abnormalities and single-gene causes. Next-generation sequencing of all the protein coding regions in the genome or targeted to genes involved in cardiac development is currently possible in the prenatal period, but there are minimal data on the clinical utility of such an approach. This study assessed the outcome of a CHD gene panel that included single-gene causes of syndromic and non-syndromic CHDs.

METHOD

Sixteen cases with a fetal CHD identified on prenatal ultrasound were studied using a 108 CHD gene panel. DNA was extracted from cultured amniocytes.

RESULTS

There was no diagnostic pathogenic variant identified in these cases. There was an average of 2.9 reportable variants identified per case and the majority of them were variants of uncertain significance.

CONCLUSION

Next-generation sequencing has the potential for increased genetic diagnosis for fetal anomalies. However, the large number of variants and the absence of an examinable patient make the interpretation of these variants challenging.

Current landscape of prenatal genetic screening and testing

Pregnant patients should be offered the option of prenatal genetic screening and diagnostic testing. The type of screening and testing offered to a patient may depend on various factors including but not limited to age, family history, fetal findings, exposures, and patient preferences. Prenatal screening is available for a variety of genetic conditions including aneuploidy, congenital abnormalities, and carrier status. Diagnostic testing options include karyotype, prenatal microarray, as well as next-generation sequencing. The various options differ in methodology, accuracy, timing and indication for testing, and information they provide. Given that the technologies related to prenatal testing are rapidly evolving and improving, the array of available screening and testing modalities are increasing. This article reviews the current offerings in prenatal screening and diagnosis.

From diagnostic yield to clinical impact: a pilot study on the implementation of prenatal exome sequencing in routine care

PURPOSE

Exome sequencing (ES) is an efficient tool to diagnose genetic disorders postnatally. Recent studies show that it may have a considerable diagnostic yield in fetuses with structural anomalies on ultrasound. We report on the clinical impact of the implementation of prenatal ES (pES) for ongoing pregnancies in routine care.

METHODS

We retrospectively analyzed the impact of pES on pregnancy outcome and pre- or perinatal management in the first 22 patients counseled for pES because of one or more structural anomalies on fetal ultrasound.

RESULTS

In two cases, a diagnosis was made by chromosomal microarray analysis after ES counseling. The remaining 20 cases were divided in three groups: (1) pES to aid parental decision making (n = 12), (2) pES in the context of late pregnancy termination requests (n = 5), and (3) pES to guide pre- or perinatal management (n = 3). pES had a clinical impact in 75% (9/12), 40% (2/5), and 100% (3/3) respectively, showing an overall clinical impact of pES of 70% (14/20).

CONCLUSION

We show that clinical implementation of pES is feasible and affects parental decision making or pre- and perinatal management supporting further implementation of ES in the prenatal setting.

Prenatal exome sequencing analysis in fetal structural anomalies detected by ultrasonography (PAGE): a cohort study

BACKGROUND

Fetal structural anomalies, which are detected by ultrasonography, have a range of genetic causes, including chromosomal aneuploidy, copy number variations (CNVs; which are detectable by chromosomal microarrays), and pathogenic sequence variants in developmental genes. Testing for aneuploidy and CNVs is routine during the investigation of fetal structural anomalies, but there is little information on the clinical usefulness of genome-wide next-generation sequencing in the prenatal setting. We therefore aimed to evaluate the proportion of fetuses with structural abnormalities that had identifiable variants in genes associated with developmental disorders when assessed with whole-exome sequencing (WES).

METHODS

In this prospective cohort study, two groups in Birmingham and London recruited patients from 34 fetal medicine units in England and Scotland. We used whole-exome sequencing (WES) to evaluate the presence of genetic variants in developmental disorder genes (diagnostic genetic variants) in a cohort of fetuses with structural anomalies and samples from their parents, after exclusion of aneuploidy and large CNVs. Women were eligible for inclusion if they were undergoing invasive testing for identified nuchal translucency or structural anomalies in their fetus, as detected by ultrasound after 11 weeks of gestation. The partners of these women also had to consent to participate. Sequencing results were interpreted with a targeted virtual gene panel for developmental disorders that comprised 1628 genes. Genetic results related to fetal structural anomaly phenotypes were then validated and reported postnatally. The primary endpoint, which was assessed in all fetuses, was the detection of diagnostic genetic variants considered to have caused the fetal developmental anomaly.

FINDINGS

The cohort was recruited between Oct 22, 2014, and June 29, 2017, and clinical data were collected until March 31, 2018. After exclusion of fetuses with aneuploidy and CNVs, 610 fetuses with structural anomalies and 1202 matched parental samples (analysed as 596 fetus-parental trios, including two sets of twins, and 14 fetus-parent dyads) were analysed by WES. After bioinformatic filtering and prioritisation according to allele frequency and effect on protein and inheritance pattern, 321 genetic variants (representing 255 potential diagnoses) were selected as potentially pathogenic genetic variants (diagnostic genetic variants), and these variants were reviewed by a multidisciplinary clinical review panel. A diagnostic genetic variant was identified in 52 (8·5%; 95% CI 6·4-11·0) of 610 fetuses assessed and an additional 24 (3·9%) fetuses had a variant of uncertain significance that had potential clinical usefulness. Detection of diagnostic genetic variants enabled us to distinguish between syndromic and non-syndromic fetal anomalies (eg, congenital heart disease only vs a syndrome with congenital heart disease and learning disability). Diagnostic genetic variants were present in 22 (15·4%) of 143 fetuses with multisystem anomalies (ie, more than one fetal structural anomaly), nine (11·1%) of 81 fetuses with cardiac anomalies, and ten (15·4%) of 65 fetuses with skeletal anomalies; these phenotypes were most commonly associated with diagnostic variants. However, diagnostic genetic variants were least common in fetuses with isolated increased nuchal translucency (≥4·0 mm) in the first trimester (in three [3·2%] of 93 fetuses).

INTERPRETATION

WES facilitates genetic diagnosis of fetal structural anomalies, which enables more accurate predictions of fetal prognosis and risk of recurrence in future pregnancies. However, the overall detection of diagnostic genetic variants in a prospectively ascertained cohort with a broad range of fetal structural anomalies is lower than that suggested by previous smaller-scale studies of fewer phenotypes. WES improved the identification of genetic disorders in fetuses with structural abnormalities; however, before clinical implementation, careful consideration should be given to case selection to maximise clinical usefulness.

FUNDING

UK Department of Health and Social Care and The Wellcome Trust.

Diagnosis of Joubert Syndrome 10 in a Fetus with Suspected Dandy-Walker Variant by WES: A Novel Splicing Mutation in OFD1

Joubert syndrome (JBTS) is a clinically and genetically heterogeneous group of ciliary diseases. To date, 34 subtypes of JBTS have been classified due to different causative genes or extra clinical features. Most of them are autosomal recessive, while only the subtype 10 (JBTS10) is a quite rare X-linked recessive disorder caused by OFD1 mutations with few reports. In this study, by using whole exome sequencing (WES), a novel OFD1 splicing mutation (c.2488+2T>C) was identified in a male fetus with suspected Dandy-Walker variant (DWV) and syndactyly, for whom abnormal karyotype and pathogenic CNV have been excluded. This mutation was inherited from the mother who has experienced two similar pregnancies before. An abnormal skipping of exon 18 in OFD1 mRNA was confirmed by RT-PCR and sequencing. Result from quantitative RT-PCR also showed that total OFD1 mRNA in the index fetus was significantly lower than the control. After a combined analysis of genetic testing results and genotype-phenotype correlations, the novel mutation c.2488+2T>C in OFD1 was considered to be the genetic cause for the affected fetus. Thus the diagnosis should be JBTS10 rather than the primary clinical diagnosis of DWV. We report the first prenatal case of JBTS10 in Chinese population, which not only helps the family to predict recurrence risks for future pregnancies but also provides more information for understanding such a rare disease. The results also present evidence that WES is an effective method in prenatal diagnosis for those fetuses with Joubert syndrome.

Clinical exome sequencing for fetuses with ultrasound abnormalities and a suspected Mendelian disorder

Background

Exome sequencing is now being incorporated into clinical care for pediatric and adult populations, but its integration into prenatal diagnosis has been more limited. One reason for this is the paucity of information about the clinical utility of exome sequencing in the prenatal setting.

Methods

We retrospectively reviewed indications, results, time to results (turnaround time, TAT), and impact of exome results for 146 consecutive “fetal exomes” performed in a clinical diagnostic laboratory between March 2012 and November 2017. We define a fetal exome as one performed on a sample obtained from a fetus or a product of conception with at least one structural anomaly detected by prenatal imaging or autopsy. Statistical comparisons were performed using Fisher’s exact test.

Results

Prenatal exome yielded an overall molecular diagnostic rate of 32% (n = 46/146). Of the 46 molecular diagnoses, 50% were autosomal dominant disorders (n = 23/46), 41% were autosomal recessive disorders (n = 19/46), and 9% were X-linked disorders (n = 4/46). The molecular diagnostic rate was highest for fetuses with anomalies affecting multiple organ systems and for fetuses with craniofacial anomalies. Out of 146 cases, a prenatal trio exome option designed for ongoing pregnancies was performed on 62 fetal specimens, resulting in a diagnostic yield of 35% with an average TAT of 14 days for initial reporting (excluding tissue culture time). The molecular diagnoses led to refined recurrence risk estimates, altered medical management, and informed reproductive planning for families.

Conclusion

Exome sequencing is a useful diagnostic tool when fetal structural anomalies suggest a genetic etiology, but other standard prenatal genetic tests did not provide a diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13073-018-0582-x) contains supplementary material, which is available to authorized users.

LMOD3-Associated Nemaline Myopathy: Prenatal Ultrasonographic, Pathologic, and Molecular Findings

To describe the prenatal presentation, including ultrasonographic, histologic, and molecular findings, in 2 fetuses affected with LMOD3-related nemaline myopathy. Prenatal ultrasonographic examinations and histopathologic studies were performed on 2 fetuses with evidence of nemaline myopathy. To establish a molecular diagnosis, whole-exome sequencing was pursued for the affected fetuses. Nemaline myopathy is a common form of congenital myopathy manifesting with nonprogressive generalized muscle weakness, hypotonia, and electron-dense protein inclusions in skeletal myofibers. Although clinically, nemaline myopathy can be viewed as a common pathway phenotype, its molecular basis is heterogeneous, with mutations in 11 identified genes implicated in its pathogenesis so far. Whole-exome sequencing revealed that the affected fetuses were compound heterozygous for 2 newly reported pathogenic variants in the LMOD3 gene, which encodes leiomodin 3. To our knowledge, this article is the first report of LMOD3-related nemaline myopathy since the original reported cohort. We provide a detailed description of the prenatal imaging of these affected fetuses, which we hope, in combination with next-generation sequencing, may contribute to further diagnosis in additional families.

Exome and genome sequencing in reproductive medicine

The advent of next-generation sequencing has enabled clinicians to assess many genes simultaneously and at high resolution. This is advantageous for diagnosing patients in whom a genetic disorder is suspected but who have a nonspecific or atypical phenotype or when the disorder has significant genetic heterogeneity. Herein, we describe common clinical applications of next-generation sequencing technology, as well as their respective benefits and limitations. We then discuss key considerations of variant interpretation and reporting, clinical utility, pre- and posttest genetic counseling, and ethical challenges. We will present these topics with an emphasis on their applicability to the reproductive medicine setting.

Diagnosis of lethal or prenatal-onset autosomal recessive disorders by parental exome sequencing

OBJECTIVE

Rare genetic disorders resulting in prenatal or neonatal death are genetically heterogeneous, but testing is often limited by the availability of fetal DNA, leaving couples without a potential prenatal test for future pregnancies. We describe our novel strategy of exome sequencing parental DNA samples to diagnose recessive monogenic disorders in an audit of the first 50 couples referred.

METHOD

Exome sequencing was carried out in a consecutive series of 50 couples who had 1 or more pregnancies affected with a lethal or prenatal-onset disorder. In all cases, there was insufficient DNA for exome sequencing of the affected fetus. Heterozygous rare variants (MAF < 0.001) in the same gene in both parents were selected for analysis. Likely, disease-causing variants were tested in fetal DNA to confirm co-segregation.

RESULTS

Parental exome analysis identified heterozygous pathogenic (or likely pathogenic) variants in 24 different genes in 26/50 couples (52%). Where 2 or more fetuses were affected, a genetic diagnosis was obtained in 18/29 cases (62%). In most cases, the clinical features were typical of the disorder, but in others, they result from a hypomorphic variant or represent the most severe form of a variable phenotypic spectrum.

CONCLUSION

We conclude that exome sequencing of parental samples is a powerful strategy with high clinical utility for the genetic diagnosis of lethal or prenatal-onset recessive disorders. © 2017 The Authors Prenatal Diagnosis published by John Wiley & Sons Ltd.

Genomic study of severe fetal anomalies and discovery of GREB1L mutations in renal agenesis

PURPOSE

Fetal anomalies represent a poorly studied group of developmental disorders. Our objective was to assess the impact of whole-exome sequencing (WES) on the investigation of these anomalies.

METHODS

We performed WES in 101 fetuses or stillborns who presented prenatally with severe anomalies, including renal a/dysgenesis, VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities), brain anomalies, suspected ciliopathies, multiple major malformations, and akinesia.

RESULTS

A molecular diagnosis was obtained in 19 cases (19%). In 13 of these cases, the diagnosis was not initially suspected by the clinicians because the phenotype was nonspecific or atypical, corresponding in some cases to the severe end of the spectrum of a known disease (e.g., MNX1-, RYR1-, or TUBB-related disorders). In addition, we identified likely pathogenic variants in genes (DSTYK, ACTB, and HIVEP2) previously associated with phenotypes that were substantially different from those found in our cases. Finally, we identified variants in novel candidate genes that were associated with perinatal lethality, including de novo mutations in GREB1L in two cases with bilateral renal agenesis, which represents a significant enrichment of such mutations in our cohort.

CONCLUSION

Our study opens a window on the distinctive genetic landscape associated with fetal anomalies and highlights the power-but also the challenges-of WES in prenatal diagnosis.

Clinical diagnostic exome evaluation for an infant with a lethal disorder: genetic diagnosis of TARP syndrome and expansion of the phenotype in a patient with a newly reported RBM10 alteration

Background

Diagnostic Exome Sequencing (DES) has been shown to be an effective tool for diagnosis individuals with suspected genetic conditions.

Case Presentation

We report a male infant born with multiple anomalies including bilateral dysplastic kidneys, cleft palate, bilateral talipes, and bilateral absence of thumbs and first toes. Prenatal testing including chromosome analysis and microarray did not identify a cause for the multiple congenital anomalies. Postnatal diagnostic exome studies (DES) were utilized to find a molecular diagnosis for the patient.

Exome sequencing of the proband, mother, and father showed a previously unreported maternally inherited RNA binding motif protein 10 (RBM10) c.1352_1353delAG (p.E451Vfs*66) alteration. Mutations in RBM10 are associated with TARP syndrome, an X-linked recessive disorder originally described with cardinal features of talipes equinovarus, atrial septal defect, Robin sequence, and persistent left superior vena cava.

Conclusion

DES established a molecular genetic diagnosis of TARP syndrome for a neonatal patient with a poor prognosis in whom traditional testing methods were uninformative and allowed for efficient diagnosis and future reproductive options for the parents. Other reported cases of TARP syndrome demonstrate significant variability in clinical phenotype. The reported features in this infant including multiple hemivertebrae, imperforate anus, aplasia of thumbs and first toes have not been reported in previous patients, thus expanding the clinical phenotype for this rare disorder.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0426-3) contains supplementary material, which is available to authorized users.

Whole-exome sequencing on deceased fetuses with ultrasound anomalies: expanding our knowledge of genetic disease during fetal development

PurposeThe aim of this study was to determine the diagnostic yield of whole-exome sequencing (WES) in fetuses with ultrasound anomalies that resulted in fetal demise or pregnancy termination. The results were also utilized to aid in the identification of candidate genes for fetal development and to expand the clinical phenotype of known genetic conditions.MethodsWES was performed on specimens from 84 deceased fetuses. Data were analyzed and final results were classified into one of four categories: positive, possible, negative, and candidate gene only. WES analysis was predominantly performed in fetus-parent trios or quads (61%, n=52).ResultsOverall, 20% (n = 17) of cases were positive, 45% (n=38) were possible, 9% (n=7) had only candidate gene variants and 26% (n = 22) tested negative. The diagnostic yield for definitive findings for trio analysis was 24% (n = 11) compared to 14% (n = 4) for singletons. The most frequently reported ultrasound anomalies were central nervous system (37%, n = 31), hydrops/edema (36%, n = 30), and cardiovascular anomalies (31%, n = 26).ConclusionOur experience supports the use of WES to identify the molecular etiology of fetal ultrasound anomalies, to identify candidate genes involved in fetal development, and to expand our knowledge of the clinical phenotype of known genetic conditions.

Prenatal DNA Sequencing: Clinical, Counseling, and Diagnostic Laboratory Considerations

Clinical diagnostic laboratories are producing next-generation sequencing-based test results that are becoming increasingly incorporated into patient care. Whole genome and exome sequencing on fetal material derived from amniocytes, chorionic villi, or products of conception is starting to be offered clinically in specialized centers, but it has not yet become routine practice. The technical, interpretation, and ethical challenges are greatest in the area of prenatal medicine because the fetus has a limited health history, and the physical examination is only indirectly available via prenatal sonography. Here, we provide an overview of these challenges and highlight the clinical utility, reporting, and counseling issues associated with prenatal DNA sequencing. Future considerations are also discussed. © 2017 John Wiley & Sons, Ltd.

Prenatal diagnosis of X-linked myopathy associated with a VMA21 gene mutation afforded through a novel targeted exome sequencing strategy applied in fetuses with abnormal ultrasound findings

Fetal malformations detected through routine prenatal ultrasound examination comprise a heterogeneous group potentially associated with genetic disorders where the underlying cause is difficult to establish. We present the prenatal diagnosis of a rare X‐linked myopathy involving a new VMA21 gene mutation, detected through a novel prenatal exome sequencing‐based approach.

Recent advances in prenatal genetic screening and testing

The introduction of new technologies has dramatically changed the current practice of prenatal screening and testing for genetic abnormalities in the fetus. Expanded carrier screening panels and non-invasive cell-free fetal DNA-based screening for aneuploidy and single-gene disorders, and more recently for subchromosomal abnormalities, have been introduced into prenatal care. More recently introduced technologies such as chromosomal microarray analysis and whole-exome sequencing can diagnose more genetic conditions on samples obtained through amniocentesis or chorionic villus sampling, including many disorders that cannot be screened for non-invasively. All of these options have benefits and limitations, and genetic counseling has become increasingly complex for providers who are responsible for guiding patients in their decisions about screening and testing before and during pregnancy.

First applications of a targeted exome sequencing approach in fetuses with ultrasound abnormalities reveals an important fraction of cases with associated gene defects

Background. Fetal malformations and other structural abnormalities are relatively frequent findings in the course of routine prenatal ultrasonographic examination. Due to their considerable genetic and clinical heterogeneity, the underlying genetic cause is often elusive and the resulting inability to provide a precise diagnosis precludes proper reproductive and fetal risk assessment. We report the development and first applications of an expanded exome sequencing-based test, coupled to a bioinformatics-driven prioritization algorithm, targeting gene disorders presenting with abnormal prenatal ultrasound findings.

Methods. We applied the testing strategy to14 euploid fetuses, from 11 on-going pregnancies and three products of abortion, all with various abnormalities or malformations detected through prenatal ultrasound examination. Whole exome sequencing (WES) was followed by variant prioritization, utilizing a custom analysis pipeline (Fetalis algorithm), targeting 758 genes associated with genetic disorders which may present with abnormal fetal ultrasound findings.

Results. A definitive or highly-likely diagnosis was made in 6 of 14 cases (43%), of which 3 were abortuses (Ellis-van Creveld syndrome, Ehlers-Danlos syndrome and Nemaline myopathy 2) and 3 involved on-going pregnancies (Citrullinemia, Noonan syndrome, PROKR2-related Kallmann syndrome). In the remaining eight on-going pregnancy cases (57%), a ZIC1 variant of unknown clinical significance was detected in one case, while in seven cases testing did not reveal any pathogenic variant(s). Pregnancies were followed-up to birth, resulting in one neonate harboring the PROKR2 mutation, presenting with isolated minor structural cardiac abnormalities, and in seven apparently healthy neonates.

Discussion. The expanded targeted exome sequencing-based approach described herein (Fetalis), provides strong evidence suggesting a definite and beneficial increase in our diagnostic capabilities in prenatal diagnosis of otherwise chromosomally balanced fetuses with troubling ultrasound abnormalities. Furthermore, the proposed targeted exome sequencing strategy, designed primarily as a diagnostic rather than a research discovery tool, overcomes many of the problems and limitations associated with clinical wide-scale WES testing in a prenatal setting.