Prenatal Whole Exome Sequencing Research Articles

Prenatal diagnosis of fetuses with ultrasound anomalies by whole-exome sequencing in Luoyang city, China.

Background: There is a great obstacle in prenatal diagnosis of fetal anomalies due to their considerable genetic and clinical heterogeneity. Whole-exome sequencing (WES) has been confirmed as a successful option for genetic diagnosis in pediatrics, but its clinical utility for prenatal diagnosis remains to be limited. Methods: A total of 60 fetuses with abnormal ultrasound findings underwent karyotyping or chromosomal microarray analysis (CMA), and those with negative results were further subjected to WES. The identified variants were classified as pathogenic or likely pathogenic (P/LP) and the variant of uncertain significance (VUS). Pregnancy outcomes were obtained through a telephone follow-up. Results: Twelve (20%, 12/60) fetuses were diagnosed to have chromosomal abnormalities using karyotyping or CMA. Of the remaining 48 cases that underwent WES, P/LP variants were identified in 14 cases (29.2%), giving an additional diagnostic yield of 23.3% (14/60). The most frequently affected organ referred for prenatal WES was the head or neck system (40%), followed by the skeletal system (39.1%). In terms of pathogenic genes, FGFR3 was the most common diagnostic gene in this cohort. For the first time, we discovered five P/LP variants involved in SEC24D, FIG4, CTNNA3, EPG5, and PKD2. In addition, we identified three VUSes that had been reported previously. Outcomes of pregnancy were available for 54 cases, of which 24 cases were terminated. Conclusion: The results confirmed that WES is a powerful tool in prenatal diagnosis, especially for fetuses with ultrasonographic anomalies that cannot be diagnosed using conventional prenatal methods. Additionally, newly identified variants will expand the phenotypic spectrum of monogenic disorders and greatly enrich the prenatal diagnostic database.

Prenatal whole-exome sequencing for fetal structural anomalies: a retrospective analysis of 145 Chinese cases

BackgroundWhole-exome sequencing (WES) significantly improves the diagnosis of the etiology of fetal structural anomalies. This study aims to evaluate the diagnostic value of prenatal WES and to investigate the pathogenic variants in structurally abnormal fetuses.MethodsWe recruited 144 fetuses with structural anomalies between 14 and 2020 and 15 December 2021 in the study. Genetic screening was performed by WES combined with karyotyping and chromosomal microarray analysis. The molecular diagnostic yield of prenatal WES for each type of fetal structural anomaly and the identified pathogenic genes and mutations were reported.ResultsIn this study, we retrospectively analyzed the clinical and genetic data of 145 structurally anomalous fetuses. These cases were classified into 9 phenotypic classes based on antenatal ultrasound findings. Thirty-eight pathogenic variants in 24 genes were identified in 35 of the 145 cases, including 14 novel variants in 13 genes (EP300, MYH3, TSC2, MMP9, CPLANE1, INVS, COL1A1, EYA1, TTC21B, MKS1, COL11A2, PDHA1 and L1CAM). Five additional pathogenic variants were classified as incidental findings. Our study showed that the overall diagnosis rate of WES was 28.1% (27/96) in the parent-fetus trio cases and 16.3% (8/49) in the proband-only cases. Fetuses with musculoskeletal anomalies had the highest diagnostic yield (51.4%, 19/37). In addition, FGFR3 and COL1A1 were the most common pathogenic genes.ConclusionsOur work expands the mutation spectrum of the genes associated with fetal structural anomalies and provides valuable information for future parental genetic counselling and pregnancy management of the structurally anomalous fetuses.

Prenatal whole-exome sequencing in fetuses with increased nuchal translucency.

Increased nuchal translucency (NT) is associated with an increased risk for genetic disorders. The aim of this study was to investigate the value of whole-exome sequencing (WES) in detecting genetic abnormalities for fetuses with isolated first-trimester increased NT. After the exclusion of aneuploidies and pathogenic copy number variants (CNVs) by quantitative fluorescent polymerase chain reaction (QF-PCR) and chromosomal microarray analysis (CMA), WES was performed on 63 fetuses with isolated first-trimester increased NT (≥3.5 mm). Overall, WES yielded a 4.8% (3/63) diagnostic rate for fetuses with isolated increased NT. Pathogenic variants were identified in 37.5% (3/8) fetuses that developed additional structural anomalies later in gestation, and no pathogenic variants were detected in increased NT that resolved or remained isolated throughout the pregnancy. This study provides powerful evidence to offer prenatal WES for increased NT only when additional abnormalities are present. Early detailed ultrasound to detect emerging anomalies can help physicians offer prenatal WES to fetuses with a greater likelihood of diagnosis.

Impact of Variation in Practice in the Prenatal Reporting of Variants of Uncertain Significance by Commercial Laboratories: Need for Greater Adherence to Published Guidelines

ABSTRACT Ultrasound will identify fetal structural anomalies in up to 2% to 3% of pregnancies; these can vary from minor isolated defects to severe multisystem abnormalities. As genetic investigations into the causes can assist with prenatal and perinatal decision-making, various tests exist to assist in this endeavor. Rapid aneuploidy detection and chromosomal microarray analysis are both used for detecting chromosomal aneuploidy and microdeletions or duplications (termed copy number variations) for pregnancies with fetal abnormalities. Approximately 6% of fetuses with identifiable structural abnormalities have pathogenic copy number variations, and 32% have an abnormal karyotype. In the last 8 years, whole exome sequencing (WES) has been used for making a genetic diagnosis in the remaining undiagnosed pregnancies, and a recent meta-analysis determined an exome sequencing diagnostic yield of 31% following nondiagnostic chromosomal microarray analysis or karyotype. Use of exome sequencing is complicated, however, by its association with possibly detecting variants of uncertain significance (VUSs) and pathogenic/likely pathogenic (P/LP) variants in genes possibly noncausal for the prenatal phenotypes. Thus, the value of reporting VUSs is under debate, with various policies worldwide. This study's purpose was to evaluate the clinical impact of WES and targeted panel implementation at the clinical level when fetal structural anomalies suggest a single underlying gene disorder or syndrome. The study focus was the frequency of reporting VUSs, the diagnostic yield, and the contribution of reported VUSs toward a final diagnosis. This retrospective chart review at the Provincial Medical Genetics Program at BC Women's Hospital in Vancouver included patients undergoing WES between January 2016 and December 2020. Amniocentesis was used for obtaining fetal samples, except for 4 cases of sample acquisition at the time of pregnancy termination. A total of 124 patients underwent prenatal WES or panel testing at different commercial laboratories following the identification of fetal structural anomalies by ultrasound. Patients had either WES (n = 90) or panel testing (n = 31), with 3 patients undergoing both, as decided by the ordering clinical geneticist. Genetic diagnoses of variants classified by the laboratory as P or LP were obtained in 20 of 93 patients (21.5%) via prenatal WES and in 9 of 34 patients (26%) who underwent panel testing. The 2 tests' overall diagnostic yield was 23%. Of these, 20 patients (69%) were diagnosed with autosomal dominant disorders. Overall, 32% of patients with panel testing and 42% of patients who had WES had at least 1 VUS, and 23% of WES and 15% of panels reported more than 1 VUS. There was great variation in the reporting of VUSs between laboratories. The study uncovered a lack of strict adherence to guidelines for reporting of prenatal VUSs among various laboratories. One weakness (and strength) of the study is its use of multiple commercial laboratories for the WES, panel testing, and VUS reporting. Although this is beneficial to gain various perspectives (such as the lack of adherence to guidelines), it also diminishes the consistency of the results across the entire study because of varied procedures for diagnoses. In conclusion, this study reports on 124 pregnancies with fetal anomalies at a large tertiary care center experiencing the provision of prenatal WES (or targeted gene panels) with variant interpretation and sequencing outsourced to various laboratories. A result of 23% diagnostic yield for WES and panel testing occurred based on the laboratory-reported LP and P variants. The large number of VUSs reported by laboratories implies significant resource implications due to the time to review evidence and further examine or investigate the fetus and/or parent. This is essential, and the authors emphasize the complex nature of the required posttest genetic counseling. Based on these results, the authors strongly encourage strict adherence to recommendations on VUS reporting in the prenatal setting, with the importance of a multidisciplinary approach bringing laboratory and clinical expertise of prenatal genomics and genetics together.

Prenatal diagnosis of recurrent hypoplastic left heart syndrome associated with MYH6 variants: a case report

BackgroundHypoplastic left heart syndrome (HLHS) is a rare but genetically complex and clinically and anatomically severe form of congenital heart disease (CHD).Case presentationHere, we report on the use of rapid prenatal whole-exome sequencing for the prenatal diagnosis of a severe case of neonatal recurrent HLHS caused by heterozygous compound variants in the MYH6 gene inherited from the (healthy) parents. MYH6 is known to be highly polymorphic; a large number of rare and common variants have variable effects on protein levels. We postulated that two hypomorphic variants led to severe CHD when associated in trans; this was consistent with the autosomal recessive pattern of inheritance. In the literature, dominant transmission of MYH6-related CHD is more frequent and is probably linked to synergistic heterozygosity or the specific combination of a single, pathogenic variant with common MYH6 variants.ConclusionsThe present report illustrates the major contribution of whole-exome sequencing (WES) in the characterization of an unusually recurrent fetal disorder and considered the role of WES in the prenatal diagnosis of disorders that do not usually have a genetic etiology.

Implementation of Exome Sequencing in Prenatal Diagnostics: Chances and Challenges

Whole exome sequencing (WES) has become part of the postnatal diagnostic work-up of both pediatric and adult patients with a range of disorders. In the last years, WES is slowly being implemented in the prenatal setting as well, although some hurdles remain, such as quantity and quality of input material, minimizing turn-around times, and ensuring consistent interpretation and reporting of variants. We present the results of 1 year of prenatal WES in a single genetic center. Twenty-eight fetus-parent trios were analyzed, of which seven (25%) showed a pathogenic or likely pathogenic variant that explained the fetal phenotype. Autosomal recessive (4), de novo (2) and dominantly inherited (1) mutations were detected. Prenatal rapid WES allows for a timely decision-making in the current pregnancy, adequate counseling with the possibility of preimplantation or prenatal genetic testing in future pregnancies and screening of the extended family. With a diagnostic yield in selected cases of 25% and a turn-around time under 4 weeks, rapid WES shows promise for becoming part of pregnancy care in fetuses with ultrasound anomalies in whom chromosomal microarray did not uncover the cause.

Piloting a multidisciplinary approach to improve outcomes of fetal whole exome sequencing: An overview of workflow and case example.

Whole exome sequencing (WES) has increasingly become integrated into prenatal care and genetic testing pathways. Current studies of prenatal WES have focused on diagnostic yield. The possibility of obtaining a variant of uncertain significance and lack of provider expertise are frequently described as common barriers to clinical integration of prenatal WES. We describe the implementation and workflow for a multidisciplinary approach to effectively integrate prenatal WES into maternal-fetal care to overcome these barriers. A multidisciplinary team reviews and approves potential cases for WES. This team reviews WES results, reclassifying variants as appropriate and provides recommendations for postnatal care. A detailed description of this workflow is provided, and a case example is included to demonstrate effectiveness of this approach. Our team has approved 62 cases for WES with 45 patients ultimately pursuing WES. We have achieved a diagnostic yield of 40% and the multidisciplinary team has played a role in variant interpretation in 50% of the reported variants of uncertain significance. This approach facilitates communication between prenatal and postnatal care teams and provides accurate interpretation and recommendations for identified fetal variants. This model can be replicated to ensure appropriate patient care and effective integration of novel genomic technologies into prenatal settings.

Prenatal imaging and whole-exome sequencing identify novel tetratricopeptide repeat domain 7A mutation in foetus with gastrointestinal atresia: a case report

BackgroundTetratricopeptide repeat domain 7A (TTC7A, chromosome 2p21) is a highly conserved structural motif essential for multiprotein scaffolding and cell survival. Fewer than 60 cases of TTC7A deficiency have been reported globally. It produces multisystemic disease phenotypes which are lethal in two-thirds of patients, with a median survival age of 12 months. It is predominantly detected postnatally, often rendering medical and surgical interventions futile.Case presentationWe report the antenatal sonographic and magnetic resonance imaging characteristics of a novel phenotype of TTC7A-deficiency presenting with gastrointestinal atresia. This has never been previously documented. The diagnosis was confirmed via whole-exome next-generation sequencing, thus facilitating prompt initiation of management and prolonging viability.ConclusionsNovel insight into the prenatal morphological characteristics of TTC7A-deficiency phenotypes expands knowledge of this rare condition. Furthermore, antenatal recognition facilitates targeted investigation, genetic counselling, and earlier multidisciplinary intervention to prolong viability of this predominantly lethal condition.

Expert consensus on the application of prenatal exome sequencing for fetal structural anomalies

Prospective research have shown that whole exome sequencing (WES) may be considered when a diagnosis cannot be obtained using routine prenatal methods, e.g., chromosomal karyotyping and copy number variation sequencing, for fetuses with significant structural anomalies. WES can increase the diagnostic rate of genetic disorders in such fetuses by 8% - 10%. Prenatal WES has been gaining wide acceptance. However, due to the limitations of fetal phenotypic evaluation and complexity of ethical issues in prenatal diagnosis, to justify and standardize the application of prenatal WES and maximize its clinical utility has become an urgent need. In view of this, a consensus has been formed by referring to the latest guidelines, expert consensus and authoritative literature. This consensus has put forward suggestions on the suitable objects of prenatal WES, pre-test consultation, sampling and laboratory testing, results report, post-test consultation, pregnancy outcome follow-up, multidisciplinary consultation of difficult cases, preservation of prenatal WES samples and data information.

Whole Exome Sequencing Analysis in Fetal Skeletal Dysplasia Detected by Ultrasonography: An Analysis of 38 Cases.

Background: Skeletal dysplasias (SDs) are a heterogeneous group of genetic disorders that primarily affect bone and cartilage. This study aims to identify the genetic causes for fetal SDs, and evaluates the diagnostic yield of prenatal whole-exome sequencing (WES) for this disorder.Methods: WES was performed on 38 fetuses with sonographically identified SDs and normal results of karyotype and single nucleotide polymorphism (SNP) analysis. Candidate variants were selected by bioinformatics analysis, and verified by Sanger sequencing.Results: WES revealed pathogenic or likely pathogenic variants associated with SDs in 65.79% (25/38) of fetuses, variants of uncertain significance (VUS) in SDs-related genes in 10.53% (4/38) cases, and incidental findings in 31.58% (12/38) fetuses. The SDs-associated variants identified in the present study affected 10 genes, and 35.71% (10/28) of the variants were novel.Conclusion: WES has a high diagnostic rate for prenatal SDs, which improves pregnancy management, prenatal counseling and recurrence risk assessment for future pregnancies. The newly identified variants expanded mutation spectrum of this disorder.

Analysis of families with fetal congenital abnormalities but negative prenatal diagnosis by whole exome sequencing

Objective: To evaluate the value of whole exome sequencing (WES) in prenatal clinical application. Methods: A total of 1 152 cases of congenital abnormal [including structural malformation, nuchal translucency (NT) thickening and intrauterine growth restriction] with traditional prenatal diagnosis [including G-band karyotype analysis and chromosome microarray analysis (CMA)] negative were analyzed. The congenital abnormal fetuses were divided into retrospective group and prospective group according to the time of WES detection, that is whether the pregnancy termination or not. According to the specific location of fetal malformation and their family history, the cohort was divided into subgroups. The clinical prognosis of all fetuses were followed up, and the effect of WES test results on pregnancy decision-making and clinical intervention were analyzed. According to the follow-up results, the data of fetuses with new phenotypes in the third trimester or after birth were re-analyzed. Results: Among 1 152 families who received WES, 5 families were excluded because of nonbiological parents. Among the remaining 1 147 families, 152 fetuses obtained positive diagnosis (13.3%,152/1 147), including 74 fetuses in the retrospective group (16.1%,74/460) and 78 fetuses in the prospective group (11.4%,78/687). In fetuses with negative CMA and G-band karyotype analysis results but new phenotypes in the third trimester or after birth, the positive rate by WES data re-analysis was 4.9% (8/163). A total of 34 (21.3%, 34/160) fetuses were directly affected by the corresponding positive molecular diagnosis. Among 68 cases of live births with diagnostic variation grade 4, 29 cases (42.7%, 29/68) received appropriate medical intervention through rapid review of WES results. Conclusions: WES could increase the detection rate of abnormal fetuses with negative G-banding karyotype analysis and CMA by 13.3%. Prenatal WES could guide pregnancy decision-making and early clinical intervention. It might be an effective strategy to pay attention to the special follow-up of the third trimester and postnatal fetus and to re-analyze the WES data.

Whole-exome sequencing increases the diagnostic rate for prenatal fetal structural anomalies

BackgroundPrenatal whole-exome sequencing (WES) is becoming increasingly used when karyotype and microarray tests are not diagnostic of fetal malformations. Although the value of WES clearly emerges in terms of higher diagnostic rates, the limitations of prenatal phenotyping together with the counseling challenges for variants of uncertain significance and incidental results suggest that the routine application of prenatal WES is not yet easy. MethodsStructurally abnormal fetuses with a mean gestational age of 24 weeks (range 13–38 weeks) were recruited from the Chong Qing Health Center for Women and Children. We performed a retrospective WES investigation in 85 fetuses, using DNA from amniotic fluid (66 samples, 77.6%), umbilical cord blood (10 samples, 11.8%), and fetal tissues (9 samples, 10.6%). Parental DNA was extracted from peripheral blood. ResultsMolecular diagnosis was obtained in 16 of the 85 fetuses (18.8%). According to the variant segregation mode and family history, 7 fetuses (43.75%) were affected by an autosomal dominant condition (6 variants were de novo and 1 variant was inherited from an unknowingly affected father), 7 fetuses (43.75%) had an autosomal recessive syndrome always associated with compound heterozygosity, and 2 fetuses (12.5%) had an X-linked condition (one mother was a carrier). In addition, the highest diagnostic rate was observed in fetuses with multisystem abnormalities (38.9%, 7/18). A variant of uncertain significance was detected in 16 samples (18.8%, 16/85). ConclusionOur study confirms that prenatal WES is an efficient tool for studying fetal abnormalities, although further improvements are needed to establish stronger fetal genotype-phenotype correlations.

Fetal Phenotype and Prenatal Diagnosis of Kabuki Syndrome

Abstract Kabuki syndrome (MIM 147920) is an autosomal dominant rare disease featured with multiple malformations and mental retardation. The main clinical manifestations of Kabuki syndrome are characteristic facial features, skeletal abnormalities, dermatoglyphic abnormalities, postpartum growth retardation, mild to moderate mental retardation, as well as other structural and functional abnormalities that may involve multiple systems. The establishment of diagnosis needs to be combined with clinical phenotype and the discovery of pathogenic mutation. Compared with the abundant descriptions and records of genotype-phenotype of postpartum patients, few prenatal diagnosis cases of Kabuki syndrome had been reported, which partially result from lacking the knowledge of its phenotype in fetuses that might suggest the diagnosis. This report performed comprehensive prenatal examinations to identify a fetus's etiology with multiple structural anomalies characterized by ascites, thickening of local skin, and cardiac abnormalities. We ruled out intrauterine infection, thalassemia, and chromosome abnormality by corresponding tests. Finally, trio whole-exome sequencing revealed a de novo heterozygous variation c.15641g > A (p.r5214h) in exon 48 of the KMT2D gene was the fetus's genetic pathogeny causing Kabuki syndrome. This result suggests that Kabuki syndrome should be in the suspected etiology list for prenatal hydrops/ascites. Our study confirmed that prenatal whole-exome sequencing is an efficient tool for diagnosing fetal abnormalities, and a multidisciplinary team is necessary for providing pregnancy guidance to patients.

Molecular diagnostic in fetuses with isolated congenital anomalies of the kidney and urinary tract by whole-exome sequencing.

BackgroundIn prenatal care, accumulating evidences has demonstrated that whole‐exome sequencing (WES) expedites the genetic diagnosis of fetal structural anomalies. However, the clinical value of WES in the diagnosis of prenatal isolated congenital anomalies of the kidney and urinary tract (CAKUT) is unknown.MethodsForty‐one fetuses with unexplained isolated CAKUT, normal karyotype and negative chromosomal microarray analysis (CMA) results, underwent WES and were accordingly grouped as (a) Group 1: complex cases with bilateral renal abnormalities (N = 19); and (b) Group 2: cases with isolated unilateral fetal renal abnormalities (N = 22).ResultsThe detection rate of WES for pathogenic variants and incidental variants was 7.32% (3/41) and 2.4% (1/41), respectively. The three pathogenic variants were identified in the genes ACTA2 (multisystem smooth muscle dysfunction syndrome), PKHD1 (autosomal recessive form of polycystic kidney disease), and PKD1 (autosomal dominant polycystic kidney disease type 1). The incidental variants were detected in genes PPM1D (syndromic neurodevelopmental disorders). Furthermore, all above fetuses carrying pathogenic variants came from bilateral kidney anomalies. Thus, the detection rate was 0 for fetuses with unilateral fetal renal abnormalities and 15.7% (3/19) for bilateral renal abnormalities.ConclusionThis cohort shows that prenatal WES is a supplementary approach for the etiologic diagnosis of unexplained isolated CAKUT with negative CMA, especially for fetuses with bilateral renal abnormality.

Whole Exome Sequencing (WES) enhances the diagnostic rate of perinatal autopsy: A prospective clinical utility trial with implications for prenatal diagnosis

Genomic classification is rapidly becoming a routine and integral part of diagnosis in pathology. Perinatal pathology is following this trend. The aims of this study were to determine the utility of WES in perinatal autopsy for congenital anomalies and to model the outcome of WES as a prenatal test. A total of 131 probands with congenital anomalies who underwent post mortem examination were referred by pathologists to the study. 82 probands were considered suitable for sequencing. The parents of 5 declined enrolment and 10 could not be consented. 67 probands were enrolled. Autopsy identified specific diagnoses in 11 cases (17%). WES identified specific diagnoses (‘pathogenic’ or ‘likely pathogenic’ variants) in 23 cases – a diagnostic rate of 35%. The combined diagnostic rate of autopsy and sequencing was 38%. A geneticist blinded to the autopsy findings reviewed the probands’ antenatal imaging reports and recommended a gene list to model the clinical utility of prenatal WES. The use of antenatal sequencing in this cohort would have identified a specific diagnosis in 18 of the 23 cases with positive sequencing findings. In conclusion, WES doubles the diagnostic rate of autopsy for congenital anomalies and our data supports the prenatal use of genomic sequencing.

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.

Whole exome sequencing for prenatal diagnosis in cases with fetal anomalies: Criteria to improve diagnostic yield.

Whole exome sequencing (WES) for prenatal diagnosis has a reported diagnostic yield of 6.2%-57%. Our aim was to identify patients with a high likelihood of genetic diagnosis using WES in cases with fetal ultrasound anomalies. This is a series of five selected cases for prenatal WES at our institution. Pregnant couples were initially identified due to fetal ultrasound anomalies. Candidates for WES for fetal diagnosis had a normal fetal karyotype and negative microarray with at least one of the following: parental consanguinity, large regions of homozygosity on fetal microarray, or high likelihood of single gene disorder based on ultrasound findings. All trios underwent sequencing of parental and fetal samples. WES was diagnostic in four of the five cases (80%). We identified two recessive conditions and two de novo mutations. Four couples consented to secondary findings and in one case, the father was found to have an MSH2 mutation associated with Lynch syndrome. The use of specific selection criteria for WES increased diagnostic yield to 80%. This is higher than previously reported. Wide application of our criteria can help identify those who may benefit most from this testing in prenatal diagnosis.

Parental perceptions of prenatal whole exome sequencing (PPPWES) study.

The objective of the study is to investigate the experiences of couples who underwent prenatal whole-exome sequencing (WES) for fetal anomalies and the amount/type of information couples want from prenatal WES. Participants in the Fetal Sequencing Study who had genetic testing for fetal anomalies were invited for a semistructured interview about their experience with prenatal WES. A constructivist grounded theory approach with an inductive coding style was used for coding and analysis. We interviewed 29 participants from 17 pregnancies. Two pregnancies had positive prenatal WES results, and 4 were terminated prior to receipt of WES results. The main themes were anxiety and stress around the time of diagnosis, education and consent for WES, coping and support while waiting for results, and receiving genetic testing results. In response to hypothetical scenarios probing the desire for uncertain results, 86% would like to be told about results for which the provider had some degree of uncertainty, and the percent desiring results decreased as the certainty of the results decreased. Participants' experience with exome sequence was similar to other prenatal genetic diagnostic tests, except for the longer wait time for results. When probed with hypothetical scenarios, participants desired more results than were provided in the study, including uncertain results that might diagnose the fetal condition. This highlights the need for specialized prenatal genetic counseling to have nuanced discussions of multiple dimensions of uncertainty with implementation of prenatal WES.

Diaphanospondylodysostosis: Refining the prenatal diagnosis of a rare skeletal disorder

Diaphanospondylodysostosis (DSD) is a rare autosomal recessive skeletal disorder, characterized mainly by ossification defects in vertebrae, thorax malformations, renal cystic dysplasia and usually death in the perinatal period. DSD is caused by mutations in the bone morphogenetic protein-binding endothelial regulator (BMPER) gene. We describe the prenatal findings of a non-consanguineous Jewish couple (shared Balkan origin), with three affected fetuses that presented with malformations in the spine and chest, reduced ossification of the skull and spine, horseshoe kidney and increased nuchal translucency. The unique combination of these ultrasound (US) features raised the possibility of DSD, which was confirmed by whole exome sequencing (WES) performed on a single fetal DNA and familial segregation. In the three fetuses, a novel homozygous mutation in BMPER (c.410T > A; p.Val137Asp) was found. This mutation, which segregated in the family, was not found in 65 controls of Jewish Balkan origin, and in several large databases. Taken together, the combination of a detailed prenatal US examination and WES may be highly effective in confirming the diagnosis of a rare genetic disease, in this case DSD.

Importance of complete phenotyping in prenatal whole exome sequencing.

Whole exome sequencing (WES) is an emerging technique in prenatal diagnosis. In this retrospective study, we examined diagnostic utility and limitations of WES in prenatal cases with structural birth defects. DNA from 20 trios (fetal and parental), with normal karyotype and microarray findings, underwent WES and variant interpretation at a reference laboratory. The WES results were later re-evaluated in our academic center utilizing prenatal and postnatal phenotyping. Initial analysis using only prenatal ultrasound findings revealed no pathogenic or likely pathogenic variants in 20 pregnancies with structural birth defects. Re-analysis of WES variants and combination of prenatal and postnatal phenotyping yielded pathogenic variants in at least 20% of cases including PORCN gene in a fetus with split-hand/foot malformation, as well as variants of uncertain significance in NEB and NOTCH1 in fetuses with postnatal muscle weakness and Adams-Oliver syndrome, respectively. Furthermore, Sanger sequencing in a patient with holoprosencephaly, elucidated by postnatal MRI, revealed a pathogenic 47-base pairs deletion in ZIC2 which was missed by prenatal WES. This study suggests that incomplete prenatal phenotyping and lack of prenatal ultrasound-genotype databases are the limiting factors for current interpretation of WES data in prenatal diagnosis. Development of prenatal phenotype-genotype databases would significantly help WES interpretation in this setting. Patients who underwent prenatal clinical WES may benefit from the re-analysis based on detailed postnatal findings.