Background Exome sequencing (ES) is becoming more widely available in prenatal diagnosis. However, data on its clinical utility and integration into clinical management remain limited in practice. Herein, we report our experience implementing prenatal ES (pES) in a large cohort of fetuses with anomalies detected by ultrasonography using a hospital-based in-house multidisciplinary team (MDT) facilitated by a three-step genotype-driven followed by phenotype-driven analysis framework. Methods We performed pES in 1618 fetal cases with positive ultrasound findings but negative for karyotyping and chromosome microarray analysis between January 2014 and October 2021, including both retrospective (n=565) and prospective (n=1053) cohorts. The diagnostic efficiency and its correlation to organ systems involved, phenotypic spectrum, and the clinical impacts of pES results on pregnancy outcomes were analyzed. Results A genotype-driven followed by phenotype-driven three-step approach was carried out in all trio pES. Step 1, a genotype-driven analysis resulted in a diagnostic rate of 11.6% (187/1618). Step 2, a phenotype-driven comprehensive analysis yielded additional diagnostic findings for another 28 cases (1.7%; 28/1618). In the final step 3, data reanalyses based on new phenotypes and/or clinical requests found molecular diagnosis in 14 additional cases (0.9%; 14/1618). Altogether, 229 fetal cases (14.2%) received a molecular diagnosis, with a higher positive rate in the retrospective than the prospective cohort (17.3% vs. 12.4%, p<0.01). The diagnostic rates were highest in fetuses with skeletal anomalies (30.4%) and multiple organ involvements (25.9%), and lowest in fetuses with chest anomalies (0%). In addition, incidental and secondary findings with childhood-onset disorders were detected in 11 (0.7%) cases. Furthermore, we described the prenatal phenotypes for the first time for 27 gene-associated conditions (20.0%, 27/135) upon a systematic analysis of the diagnosed cases and expanded the phenotype spectrum for 26 (19.3%) genes where limited fetal phenotypic information was available. In the prospective cohort, the combined prenatal ultrasound and pES results had significantly impacted the clinical decisions (61.5%, 648/1053). Conclusions The genotype-driven approach could identify about 81.7% positive cases (11.6% of the total cohort) with the initial limited fetal phenotype information considered. The following two steps of phenotype-driven analysis and data reanalyses helped us find the causative variants in an additional 2.6% of the entire cohort (18.3% of all positive findings). Our extensive phenotype analysis on a large number of molecularly confirmed prenatal cases had greatly enriched our current knowledge on fetal phenotype-genotype correlation, which may guide more focused prenatal ultrasound in the future. This is by far the largest pES cohort study that combines a robust trio sequence data analysis, systematic phenotype-genotype correlation, and well-established MDT in a single prenatal clinical setting. This work underlines the value of pES as an essential component in prenatal diagnosis in guiding medical management and parental decision making.

Background There are a few literature reports of prenatal ultrasound manifestations of Williams-Beuren syndrome. We aimed to explore the prenatal diagnosis of Williams-Beuren syndrome by ultrasound and chromosomal microarray analysis and describe the prenatal ultrasound performance of this syndrome. Methods In this retrospective study, we reported eight cases of Williams-Beuren syndrome diagnosed at our prenatal diagnostic center from 2016 to 2021. We systematically reviewed clinical data from these cases, including indications for invasive testing, sonographic findings, QF-PCR results, chromosomal microarray analysis results, and pregnancy outcomes. Results In this study, the common ultrasound features were ventricular septal defect (37.5%), intrauterine growth retardation (25%), and aortic coarctation (25%). Moreover, all patients were found to have a common deletion in the Williams-Beuren syndrome chromosome region at the 7q11.23 locus, which contained the elastin gene. Deletion sizes ranged from 1.42 to 2.07 Mb. Seven parents asked for termination of pregnancy, and one patient was lost to follow-up. Conclusions This study is the most extensive prenatal study using chromosomal microarray analysis technology for detailed molecular analysis of Williams-Beuren syndrome cases. We reported three cases combined with first-reported ultrasound manifestations. Case 1 was concomitant with multicystic dysplastic kidney and duodenal atresia combined with case 3. Notably, case 4 was combined with multiple cardiovascular malformations: Tetralogy of Fallot, right aortic arch, and supravalvar aortic stenosis. These manifestations expand the intrauterine ultrasound phenotype of Williams-Beuren syndrome in previous literature reports.

Objective:We aimed to investigate the value of exome sequencing (ES) in fetuses with callosal anomalies (CA) with or without other structural anomalies, but with normal findings by karyotyping and chromosome microarray analysis (CMA).Methods: Cases with CA with or without other structural anomalies were screened for eligibility. Fetuses with abnormal karyotyping or CMA results were excluded.We performed ES on DNA samples from eligible fetus-parental trios and identified diagnostic genetic variants based on the ultrasonographic features.Results: A total of 50 eligible fetus-parental trios were successfully analyzed by ES.We found 17 likely pathogenic or pathogenic variants in 14 genes from 17 fetuses, with a total proportion of diagnostic genetic variants equal to 34.0% (17/50). Of the 17 cases with a diagnosis, 10 (29.4%, 10/35) were isolated and 7 (43.8%, 7/15) were non-isolated. Pregnancy outcome data showed that 70.0% (7/10) of the surviving isolated CA fetuses with negative ES results had a good prognosis in early childhood.Conclusions: Our study used ES prenatally for CA and showed that ES can be used diagnostically to define the molecular defects that underlie unexplained CA. Most subjects with isolated CA with negative results for genetic causes will have a favorable prognosis in early childhood.

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