Exome Sequencing and Its Emerging Role in Prenatal Genetic Diagnosis

Exploring prenatal testing preferences among US pregnant individuals: A discrete choice experiment

Although there are numerous benefits to diagnostic prenatal testing, such as fetal exome sequencing, there are also consequences, including the possibility of receiving variants of uncertain significance or identifying secondary findings. In this study, we utilized a survey-based discrete choice experiment to elicit the preferences of pregnant people in Northern California for hypothetical prenatal genomic tests. Pregnant individuals were invited to complete the survey through advertisements on social media. Five test attributes were studied: likelihood of getting a result, time taken to receive results, who explains results, reporting of uncertain results, and reporting of secondary findings. The survey also gathered information about the participants' demographics, current and past pregnancies, and tolerance of uncertainty using the IUS-12 scale. Participants were eligible if they were female, currently 24 or more weeks pregnant, and able to read/write enough English or Spanish to complete an online survey. Overall, participants (n = 56) preferred the option of having a prenatal test over not having a prenatal test (p < 0.01) and had substantially higher preferences for tests with the highest likelihood of getting a result (p < 0.01). There were also positive preferences for tests that reported secondary findings (p = 0.01) and those where results were returned by a genetic specialist (vs. their prenatal provider) (p = 0.04). These findings can be used to guide conversations between pregnant individuals and genetics specialists, such as genetic counselors, as they weigh the pros and cons of diagnostic prenatal testing options.

Diagnostic yield of exome sequencing in prenatal agenesis of corpus callosum: systematic review and meta-analysis

OBJECTIVES

To determine the incremental diagnostic yield of exome sequencing (ES) after negative chromosomal microarray analysis (CMA) in cases of prenatally diagnosed agenesis of the corpus callosum (ACC) and to identify the associated genes and variants.

METHODS

A systematic search was performed to identify relevant studies published up until June 2022 using four databases: PubMed, SCOPUS, Web of Science and The Cochrane Library. Studies in English reporting on the diagnostic yield of ES following negative CMA in prenatally diagnosed partial or complete ACC were included. Authors of cohort studies were contacted for individual participant data and extended cohorts were provided for two of them. The increase in diagnostic yield with ES for pathogenic/likely pathogenic (P/LP) variants was assessed in all cases of ACC, isolated ACC, ACC with other cranial anomalies and ACC with extracranial anomalies. To identify all reported genetic variants, the systematic review included all ACC cases; however, for the meta-analysis, only studies with ≥ three ACC cases were included. Meta-analysis of proportions was employed using a random-effects model. Quality assessment of the included studies was performed using modified Standards for Reporting of Diagnostic Accuracy criteria.

RESULTS

A total of 28 studies, encompassing 288 prenatally diagnosed ACC cases that underwent ES following negative CMA, met the inclusion criteria of the systematic review. We classified 116 genetic variants in 83 genes associated with prenatal ACC with a full phenotypic description. There were 15 studies, encompassing 268 cases, that reported on ≥ three ACC cases and were included in the meta-analysis. Of all the included cases, 43% had a P/LP variant on ES. The highest yield was for ACC with extracranial anomalies (55% (95% CI, 35-73%)), followed by ACC with other cranial anomalies (43% (95% CI, 30-57%)) and isolated ACC (32% (95% CI, 18-51%)).

CONCLUSIONS

ES demonstrated an incremental diagnostic yield in cases of prenatally diagnosed ACC following negative CMA. While the greatest diagnostic yield was observed in ACC with extracranial anomalies and ACC with other central nervous system anomalies, ES should also be considered in cases of isolated ACC. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Prenatal diagnosis of Freeman-Sheldon syndrome using ultrasound and genetic testing. Case report

Objectives

To describe a case of prenatal diagnosis of Freeman-Sheldon syndrome based on ultrasound findings and complete fetal exome sequencing.

Materials and methods

A 33-year-old patient currently on treatment for hypothyroidism in whom a 19-week detailed anatomical ultrasound scan showed fetal deformities in more than two body areas (upper and lower limbs), suggesting a diagnosis of arthrogryposis. Genetic counseling was provided and amniocentesis was performed at 20 weeks for fluorescence in situ hybridization (FISH) analysis and complete fetal exome sequencing, with the latter allowing the identification of a heterozygous pathogenic variant of the MYH3 gene which is associated with type 2A distal arthrogryposis.

Conclusions

Complete fetal exome sequencing was a key factor in identifying the MYH3 gene mutation and confirmed that the deformities seen on ultrasound were associated with type 2A distal arthrogryposis. It is important to perform complete fetal exome sequencing in cases of joint malformations seen on prenatal ultrasound.

Prenatal diagnosis of paternal uniparental disomy for chromosome 2 in two fetuses with intrauterine growth restriction

Uniparental disomy (UPD) is when all or part of the homologous chromosomes are inherited from only one of the two parents. Currently, UPD has been reported to occur for almost all chromosomes. In this study, we report two cases of UPD for chromosome 2 (UPD2) encountered during prenatal diagnosis. The ultrasound findings of the fetuses from two unrelated families showed intrauterine growth restriction. The karyotype analyses were normal. The two fetuses both had complete paternal chromosome 2 uniparental disomy detected by whole-exome sequencing, but their clinical outcomes were significantly different, with fetal arrest in case 1 and birth in case 2. In this report, we analyzed and discussed the phenotypes of the fetuses in these two cases and reviewed the literature on UPD2.

Information is power: The experiences, attitudes and needs of individuals who chose to have prenatal genomic sequencing for fetal anomalies

OBJECTIVE

This study sought to evaluate the experiences of individuals who chose to participate in a study and receive prenatal genomic sequencing (pGS) for fetuses with congenital structural anomalies.

METHOD

Individuals who received research results of prenatal sequencing were invited to participate in semi-structured interviews about their experiences. A constructivist grounded theory approach was used to code and analyze interviews.

RESULTS

Thirty-three participants from 27 pregnancies were interviewed. Participants were motivated to enroll in the study to find out more about their fetus' condition and prepare for the future. The waiting period was a time of significant anxiety for participants. Most participants felt relief and closure upon receiving results, regardless of the category of result, and had a clear understanding of the implications of the results.

CONCLUSION

Participants' experiences with pGS were often intertwined with the experience of having a fetus with an abnormality. Participants were satisfied with the decision to participate in research and the support they received from the healthcare team, although waiting for results was associated with anxiety. The healthcare team plays an integral role in setting expectations and validating feelings of anxiety, fear and uncertainty.