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Objective: Prenatally detected central nervous system (CNS) anomalies present a diagnostic challenge. In this study, we compared the diagnostic yield of exome sequencing (ES) and chromosomal microarray analysis (CMA) in fetuses with a major CNS anomaly.Methods: This was a retrospective study of 114 cases referred for genetic evaluation following termination of pregnancy (TOP) due to a major CNS anomaly detected on prenatal ultrasound. All fetuses were first analyzed by CMA. All CMA-negative cases were offered ES. CMA-positive cases were reanalyzed using ES to assess its ability to detect copy-number variants (CNVs).Results: CMA identified a pathogenic or likely pathogenic (P/LP) CNV in 11/114 (10%) cases. Eighty-six CMA-negative cases were analyzed using ES, which detected P/LP sequence variants in 38/86 (44%). Among recurrent cases (i.e. cases with a previously affected pregnancy), the incidence of P/LP sequence variants was non-significantly higher compared with non-recurrent ones (12/19 (63%) vs 26/67 (39%); P = 0.06). Among the 38 cases with an ES diagnosis, 20 (53%) were inherited and carried a significant risk of recurrence. Reanalysis of 10 CMA-positive cases by ES demonstrated that the bioinformatics pipeline used for sequence variant analysis also detected all P/LP CNVs, as well as three previously known non-causative CNVs.Conclusions: In our study, ES provided a high diagnostic yield (> 50%) in fetuses with severe CNS structural anomalies, which may have been partly due to the highly selected case series that included post-TOP cases from a specialist referral center. These data suggest that ES may be considered as a first-tier test for the prenatal diagnosis of major fetal CNS anomalies, detecting both P/LP sequence variants and CNVs. This is of particular importance given the time constraints of an ongoing pregnancy and the risk of recurrence in future pregnancies. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

This has been discussed in detail in a recent systematic review by Mellis I et al i .[2], demonstrating that the incremental diagnostic yield of ES over CMA/karyotyping was 15% for non-selected fetal anomalies, 42% for selected anomalies and 17% for CNS anomalies. While patients were offered concurrent chromosomal microarray analysis (CMA) and exome sequencing (ES), most opted for termination of pregnancy even before receiving a genetic test result due to the severity of anomalies and because ES in pregnancy is currently not covered by the Israeli healthcare system. Even if the fetal phenotype may not appear to be severe enough to warrant termination of pregnancy, a genetic test result may point to a severe neurodevelopmental issue that has only mild physical manifestations. [Extracted from the article]

The authors of the article titled "Unique prenatal manifestations of biallelic NDUFAF5 variants: expansion of phenotype" respond to comments made by Dr. Finsterer. They clarify that their study did not report on cases of intrauterine fetal death, but rather on cases of termination due to fetal anomalies. They also explain that functional or biochemical testing is not mandatory for determining variant pathogenicity according to the American College of Medical Genetics and Genomics guidelines. The authors provide evidence supporting the pathogenicity of the NDUFAF5 variants they studied and acknowledge the need for further research on one of the variants. They assert that their study contributes to the understanding of prenatal presentations of NDUFAF5-associated disorders and emphasize the challenges of studying prenatal phenotypes. The authors address Dr. Finsterer's mention of other possible abnormalities associated with NDUFAF5 variants and state that the lack of demonstration does not negate their assumption that these variants are causative of the congenital anomalies described in their study. They also clarify that family history and parental carrier status were included in their original manuscript. [Extracted from the article]

The article presents the author's views on the non-invasive prenatal testing (NIPT) for pregnant women who want to detect trisomy 21 in their unborn child. It states that NIPT improve the quality of prenatal testing for fetal abnormalities. It further discusses aneuploidy screening, chromosomal microarray analysis and testing in pregnancy.

Objective: Mitochondrial complex‐I deficiency, nuclear type 16, is a rare autosomal recessive disorder caused by biallelic pathogenic variants in NDUFAF5 (C20orf7) (OMIM 618238). The aim of this study was to describe a severe early prenatal manifestation of this disorder, which was previously considered to occur only postnatally. Methods: This was a multicenter retrospective case series including five fetuses from three non‐related families, which shared common sonographic abnormalities, including brain cysts, corpus callosal malformations, non‐immune hydrops fetalis and growth restriction. Genetic evaluation included chromosomal microarray analysis and exome sequencing. Two fetuses from the same family were also available for pathology examination, including electron microscopy. Results: Chromosomal microarray analysis revealed no chromosomal abnormality in any of the tested cases. Trio exome sequencing demonstrated that three affected fetuses from three unrelated families were compound heterozygous or homozygous for likely pathogenic variants in NDUFAF5. No other causative variants were detected. The association between NDUFAF5 variants and fetal malformations was further confirmed by segregation analysis. Histological evaluation of fetal tissues and electron microscopy of the skeletal muscle, liver, proximal tubules and heart demonstrated changes that resembled postmortem findings in patients with mitochondrial depletion disorders as well as previously undescribed findings. Conclusions: Mitochondrial complex‐I deficiency and specifically biallelic mutations in NDUFAF5 have a role in abnormal fetal development, presenting with severe congenital malformations. Mitochondrial complex‐I disorders should be considered in the differential diagnosis of corpus callosal malformations and brain cysts, especially when associated with extracranial abnormalities, such as fetal growth restriction and non‐immune hydrops fetalis. © 2023 International Society of Ultrasound in Obstetrics and Gynecology. Linked article: There is a comment on this article by Finsterer. Click here to view the Correspondence. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In addition to ventriculomegaly, abnormal corpus callosum and adducted thumbs, fetal MRI has also detected diencephalic and midbrain-hindbrain malformations in most fetuses affected by the L1 syndrome. L1 syndrome includes a spectrum of X-linked disorders caused by pathogenic variants of L1CAM gene, which encodes a cell adhesion molecule involved in the central nervous system (CNS) development. In addition to the evaluation of lateral ventricles, corpus callosum and cortical development, thalami and midbrain-hindbrain were investigated. [Extracted from the article]

OC12.05: Early second trimester diagnosis of fetal midbrain-hindbrain malformations: a transvaginal neurosonographic study To describe the clinical and neurosonographic features of fetal midbrain-hindbrain (MBHB malformation diagnosed at 14-18 weeks. The MBHB abnormalities include; kinking of the brainstem (KBS) (n = 3), Joubert syndrome (JS) (n = 2), aqueductal stenosis (AS) (n = 11), rhombencephalosynapsis (RES) (n = 3), "open" fourth ventricle (OFV) (n = 6), and Mobius syndrome (MS) (n = 1). [Extracted from the article]

The article considers the benefits of contingent screening against primary screening by cell-free DNA testing. Topics discussed include non-invasive prenatal testing (NIPT) via cell-free DNA analysis, NIPT implementation in public-health-based programs, and the lack of evidence for additional perceived benefits of serum screening or nuchal translucency (NT) measurement.

Variants of unknown significance (VUS) poses a dilemma in prenatal genetic testing and counselling. Methods Cases were selected from a cohort of 87 patients who underwent TOP for major CNS anomalies and presented VUS either in genetic assessment. [Extracted from the article]

Fetal imaging findings (US, MRI or both) of fetuses with copy number variants (CNVs) or pathogenic/likely pathogenic sequence variants (SVs) were compared to the classical phenotype described by the literature. OC01.02: Genotype-phenotype correlation in fetuses with major brain malformations using whole-exome sequencing When performing fetal ultrasound (US) we are confronted with the difficult task of finding a correlation between imaging findings, diagnosis and prognosis. [Extracted from the article]

OC06.07: Maternal plasma genome-wide cell-free DNA testing can detect fetal aneuploidy in pregnancy loss and can be used to guide further work-up in recurrent losses However, the most common cause of miscarriage, even in RPLs, is random chromosomal aberrations (trisomy, monosomy, triploidy). We suggest that cfDNA-based testing serve to guide management in RPLs: if cfDNA in the 2nd and subsequent RPL demonstrates aneuploidy, no further action is taken; if cfDNA demonstrates an unbalanced rearrangement, parental karyotypes is recommended; and if no abnormality is detected, then the recommended RPL workup is performed. [Extracted from the article]