Exome sequencing vs targeted gene panels for the evaluation of nonimmune hydrops fetalis

Fetal Hydrops: Genetic Dissection of an Unspecific Sonographic Finding-A Comprehensive Review

Fetal hydrops is defined as the presence of abnormal fluid collections in two or more intra-fetal compartments. It has been classified based on etiology (immune vs. non-immune), on the presence or absence of other findings (isolated vs. non-isolated) and on the gestational age at presentation (first-, second- or third-trimester). In all cases of non-immune hydrops fetalis, invasive prenatal diagnosis is offered. However, after cytogenetic analyses, 80% of fetuses remain without etiological diagnosis, not allowing one to define the prognosis and to formulate recurrence risks. Several geneticists recommend performing either a next-generation sequencing panel (commonly limited to RASopathy testing) or exome sequencing, if cytogenetic tests are inconclusive. In the literature, the data are extremely heterogeneous, due to the differences in these indications and the limitation of study to a select group of genes. The identification of the underlying cause is crucial, as prognostic information and even therapy options are becoming increasingly available for a wide and growing array of genetic conditions. A systematic approach would allow an overall evaluation of the diagnostic rate of the exome sequencing in fetal effusions, also calculating the prevalence of associated diseases, with the aim of obtaining a diagnosis, defining the most appropriate management for each case, and broadening the spectrum of conditions known to be associated with hydrops.

Fetal imaging, phenotyping, and genomic testing in modern prenatal diagnosis

Genetic tests available in the prenatal setting have expanded rapidly with next generation sequencing, and fetal imaging can detect a breadth of many structural and functional abnormalities. To identify a fetal genetic disease, deep phenotyping is increasingly important to generate a differential diagnosis, choose the most appropriate genetic tests, and inform the results of those tests. The Human Phenotype Ontology (HPO) organizes and defines the features of human disease to support deep phenotyping, and ongoing efforts are being made to improve the scope of the HPO to comprehensively include fetal phenotypes. There are important limitations of fetal phenotyping to understand, including ongoing structural development and limited knowledge of how many genetic diseases present uniquely in utero. This article provides an overview of the use of HPO terms and artificial intelligence in the approach to fetal phenotyping and genetic testing.

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.

The Conundrum of Mechanics Versus Genetics in Congenital Hydrocephalus and Its Implications for Fetal Therapy Approaches: A Scoping Review

Recent advances in gene therapy, particularly for single-gene disorders (SGDs), have led to significant progress in developing innovative precision medicine approaches that hold promise for treating conditions such as primary hydrocephalus (CH), which is characterized by increased cerebrospinal fluid (CSF) volumes and cerebral ventricular dilation as a result of impaired brain development, often due to genetic causes. CH is a significant contributor to childhood morbidity and mortality and a driver of healthcare costs. In many cases, prenatal ultrasound can readily identify ventriculomegaly as early as 14-20 weeks of gestation, with severe cases showing poor neurodevelopmental outcomes. Postnatal surgical approaches, such as ventriculoperitoneal shunts, do not address the underlying genetic causes, have high complication rates, and result in a marginal improvement of neurocognitive deficits. Prenatal somatic cell gene therapy (PSCGT) promises a novel approach to conditions such as CH by targeting genetic mutations in utero, potentially improving long-term outcomes. To better understand the pathophysiology, genetic basis, and molecular pathomechanisms of CH, we conducted a scoping review of the literature that identified over 160 published genes linked to CH. Mutations in L1CAM, TRIM71, MPDZ, and CCDC88C play a critical role in neural stem cell development, subventricular zone architecture, and the maintenance of the neural stem cell niche, driving the development of CH. Early prenatal interventions targeting these genes could curb the development of the expected CH phenotype, improve neurodevelopmental outcomes, and possibly limit the need for surgical approaches. However, further research is needed to establish robust genotype-phenotype correlations and develop safe and effective PSCGT strategies for CH.

Molecular diagnostic yield for Blau syndrome in previously diagnosed juvenile idiopathic arthritis with uveitis or cutaneous lesions

OBJECTIVE

Diagnostic pitfalls often arise in the community because of potentially misleading similarities between juvenile idiopathic arthritis (JIA) and Blau syndrome, an immune-related disorder caused by NOD2 gene mutations. It remains unclear in which population and to what extent next-generation sequencing techniques can aid in diagnosis.

METHODS

We evaluated clinical usefulness of targeted next-generation sequencing in previously diagnosed JIA. Participants were required to have symptoms and signs suspected of Blau syndrome, including at least uveitis or cutaneous lesions in addition to arthritis. Targeted sequencing was conducted on NOD2 gene to detect diagnostic variants classified as pathogenic or likely pathogenic for Blau syndrome. We assessed the molecular diagnostic yield and clinical implications for patient care.

RESULTS

Between 1 May 2008 and 1 June 2021, sequencing data were accrued from 123 previously diagnosed JIA (median age: 5 years; female: 62.6%). Targeted NOD2 sequencing yielded a positive molecular diagnosis of Blau syndrome in 21.1% (95% CI: 14.9%, 29.2%), encompassing six heterozygous missense mutations classified as pathogenic variants. Among those receiving a molecular diagnosis, changes in clinical management and treatment were considered as having occurred in 38.5%. Nine predictors were identified as being associated with a higher diagnostic yield, providing clinical clues to suspect the possibility of Blau syndrome.

CONCLUSION

Among some patients with paediatric-onset arthritis complicated with uveitis or cutaneous lesions, reassessment of the diagnosis of JIA may be warranted. Targeted NOD2 sequencing established the molecular diagnosis of Blau syndrome in nearly one-fifth of these cases and provided clinically relevant information for patient-care decisions.

Nonimmune Hydrops Fetalis

Nonimmune hydrops fetalis (NIHF) poses a significant challenge in perinatal care due to its high mortality rates and diverse etiologies. This comprehensive review examines the pathophysiology, etiology, antenatal diagnosis and management, postnatal care, and outcomes of NIHF. NIHF arises from numerous underlying pathologies, including genetic disorders, cardiovascular causes, and fetal infections, with advances in diagnostic techniques improving identification rates. Management strategies include termination of pregnancy for severe cases and fetal therapy for selected treatable etiologies, and neonatal care involves assessing and treating fluid collections and identifying underlying causes. Prognosis depends on factors such as gestational age at diagnosis and the extent of resuscitation needed, with challenges remaining in improving outcomes for affected infants.

Paired comparison of the analytical performance between the Oncomine™ Comprehensive Assay v3 and whole-exome sequencing of ovarian cancer tissue

BACKGROUND

Next-generation sequencing (NGS) has been implemented in clinical oncology as a personalized medicine tool to identify targetable genetic alterations and to guide treatment decisions. However, the optimal NGS test strategy and target genes for clinical use are still being discussed. The aim was to compare the performance of the Oncomine™ Comprehensive Assay v3 (OCAv3) (targeted gene panel) and whole-exome sequencing (WES) to investigate somatic single and multiple nucleotide variants and small indels in ovarian cancer patients.

METHODS AND RESULTS

Genomic DNA was isolated from fresh frozen samples of five high-grade serous (HGSC) and three clear cell ovarian (oCCC) cancer patients. Exome sequencing libraries were prepared by using the Ion AmpliSeq Exome RDY kit, whereas libraries for OCAv3 were prepared using by Ion AmpliSeq™ Library Kit Plus. Sequencing was performed using the Ion S5XL System (Thermo Fisher Scientific). When including only variants classified as pathogenic, likely pathogenic or unknown significance based on ClinVar database verdicts and comparing overlapping regions covered both by the OCAv3 assay and WES, 23 variants were detected by both assays. However, OCAv3 detected additionally two variants: ARID1A: p.Gln563Ter and TP53: p.Ser261ValfsTer84 that have not passed WES filtering criteria due to low coverage.

CONCLUSIONS

With the present treatment possibilities, OCAv3 panel testing provided higher diagnostic yield due to better coverage. Our study emphasizes that WES, although offering the potential to identify novel findings in genes not covered by OCAv3, might overlook variants in genes relevant for OC.

Prenatal Management and Perinatal Outcome in a Large Series of Hydrops Fetalis

INTRODUCTION

Nonimmune hydrops fetalis (NIHF) is the most frequent etiology of hydrops fetalis (HF), accounting for around 95% of cases. It associates high perinatal mortality and morbidity rates. The aim of the study was, first, to investigate etiology, prenatal management, and perinatal outcome in a large single-center series of HF; second, to identify prenatal prognostic factors with impact on perinatal outcome.

MATERIALS AND METHODS

Observational retrospective study of 80 HF diagnosed or referred to a single tertiary center between 2012 and 2021. Clinical characteristics, etiology, prenatal management, and perinatal outcome were recorded. Adverse perinatal outcome was defined as intrauterine fetal death (IUFD), early neonatal death (first 7 days of life) and late neonatal death (between 7 and 28 days).

RESULTS

Seventy-six of the 80 cases (95%) were NIHF, main etiology being genetic disorders (28/76; 36.8%). A total of 26 women (32.5%) opted for termination of pregnancy, all of them in the NIHF group. IUFD occurred in 24 of 54 patients (44.4%) who decided to continue the pregnancy. Intrauterine treatment was performed in 29 cases (53.7%). There were 30 newborns (55.6%). Adverse perinatal outcome rate was 53.7% (29/54), significantly higher in those diagnosed <20 weeks of gestation (82.4% < 20 weeks vs. 40.5% ≥ 20 weeks; p = 0.004). Survival rate was higher when fetal therapy was performed compared to the expectantly managed group (58.6% vs. 32%; p = 0.05). Intrauterine blood transfusion and thoraco-amniotic shunt were the procedures that achieved the highest survival rates (88.9% and 100%, respectively, p = 0.003).

CONCLUSION

NIHF represented 95% of HF with genetic disorders as the main etiology. Most of them were diagnosed before 20 weeks of gestation, with worse prognosis than cases detected later in gestation. Rates of TOP, IUFD, and early neonatal death were higher in NIHF. Intrauterine therapy, when indicated, improved the perinatal outcome.

Persistent chylothorax associated with lymphatic malformation type 6 due to biallelic pathogenic variants in PIEZO1

PIEZO1 is required for lymphatic valve formation, and several lymphatic abnormalities have been reported to be associated with autosomal recessive PIEZO1 pathogenic variants including neonatal hydrops, lymphedema involving various body regions, and chylothorax. Persistent or recurrent chylothorax has been infrequently described in association with pathogenic variants in the PIEZO1 gene. We present a 4-year-old female with bilateral pleural effusions detected prenatally, who was diagnosed with bilateral chylothoraces post-partum. She subsequently had recurrent pleural effusions involving both pleural cavities, which tended to improve with restriction of her fat intake, and, one occasion, subcutaneous octreotide. She also had bilateral calf, and intermittent cheek swelling. Genetic testing revealed two deleterious variants in PIEZO1: c.2330-2_2330-1del and c.3860G > A (p.Trp1287*), both of which were classified as likely pathogenic. This supported a diagnosis of Lymphatic Malformation Type 6 (OMIM 616843), also known as Hereditary Lymphedema Type III. Hereditary Lymphedema type III can be associated with persistent chylothorax that can vary in size over time.

Investigation into the genetics of fetal congenital lymphatic anomalies

OBJECTIVE

Congenital lymphatic anomalies (LAs) arise due to defects in lymphatic development and often present in utero as pleural effusion, chylothorax, nuchal and soft tissue edema, ascites, or hydrops. Many LAs are caused by single nucleotide variants, which are not detected on routine prenatal testing.

METHODS

Demographic data were compared between two subcohorts, those with clinically significant fetal edema (CSFE) and isolated fetal edema. A targeted variant analysis of LA genes was performed using American College of Medical Genetics criteria on whole exome sequencing (WES) data generated for 71 fetal edema cases who remained undiagnosed after standard workup.

RESULTS

CSFE cases had poor outcomes, including preterm delivery, demise, and maternal preeclampsia. Pathogenic and likely pathogenic variants were identified in 7% (5/71) of cases, including variants in RASopathy genes, RASA1, SOS1, PTPN11, and a novel PIEZO1 variant. Variants of uncertain significance (VOUS) were identified in 45% (32/71) of cases. In CSFEs, VOUS were found in CELSR1, EPHB4, TIE1, PIEZO1, ITGA9, RASopathy genes, SOS1, SOS2, and RAF1.

CONCLUSIONS

WES identified pathogenic and likely pathogenic variants and VOUS in LA genes in 51% of fetal edema cases, supporting WES and expanded hydrops panels in cases of idiopathic fetal hydrops and fluid collections.

Prenatal exome and genome sequencing for fetal structural abnormalities

As prenatal exome sequencing becomes integrated into clinical care, it is critical that providers caring for women with fetal anomalies recognize not only the benefits, but also the challenges and considerations related to this technology. This overview of prenatal sequencing includes information about indications for sequencing, methods, diagnostic yield, clinical utility, variant interpretation, ethical considerations and dilemmas, practical considerations (ie, turnaround time and cost), pre- and posttest counseling points, and psychological impact of testing on families.

Genetics in prenatal diagnosis

The options for prenatal genetic testing have evolved rapidly in the past decade, and advances in sequencing technology now allow genetic diagnoses to be made down to the single-base-pair level, even before the birth of the child. This offers women the opportunity to obtain information regarding the foetus, thereby empowering them to make informed decisions about their pregnancy. As genetic testing becomes increasingly available to women, clinician knowledge and awareness of the options available to women is of great importance. Additionally, comprehensive pretest and posttest genetic counselling about the advantages, pitfalls and limitations of genetic testing should be provided to all women. This review article aims to cover the range of genetic tests currently available in prenatal screening and diagnosis, their current applications and limitations in clinical practice as well as what the future holds for prenatal genetics.

A Pain in the Neck: Lessons Learnt from Genetic Testing in Fetuses Detected with Nuchal Fluid Collections, Increased Nuchal Translucency versus Cystic Hygroma-Systematic Review of the Literature, Meta-Analysis and Case Series

Fetal Nuchal fluid collections can manifest with two distinct presentations attributable to the same phenotypic spectrum: increased nuchal translucency (iNT) and cystic hygroma. The prenatal detection of these findings should prompt an accurate assessment through genetic counseling and testing, including karyotype, chromosomal microarray analysis (CMA) and multigene RASopathy panel. We performed a systematic review of the literature and meta-analysis, to calculate diagnostic yields of genetic testing in fetuses with iNT and cystic hygroma. We compared the results with a cohort of 96 fetuses with these isolated findings. Fetuses with isolated NT ≥ 2.5 mm showed karyotype anomalies in 22.76% of cases and CMA presented an incremental detection rate of 2.35%. Fetuses with isolated NT ≥ 3 mm presented aneuploidies in 14.36% of cases and CMA had an incremental detection rate of 3.89%. When the isolated NT measured at least 3.5 mm the diagnostic yield of karyotyping was 34.35%, the incremental CMA detection rate was 4.1%, the incremental diagnostic rate of the RASopathy panel was 1.44% and it was 2.44% for exome sequencing. Interestingly, CMA presents a considerable diagnostic yield in the group of fetuses with NT ≥ 3.5 mm. Similarly, exome sequencing appears to show promising results and could be considered after a negative CMA result.

An Investigation of the Etiologies of Non-Immune Hydrops Fetalis in the Era of Next-Generation Sequence-A Single Center Experience

(1) Background: Numerous etiologies may lead to non-immune hydrops fetalis (NIHF). However, the causes remain unclear in half of NIHF cases following current standard assessment. The application of prenatal chromosomal microarray analysis (CMA) and exome sequencing (ES) can improve the identification of the etiologies. This study aimed to investigate the etiologies of NIHF in the era of next-generation sequence (NGS) following a unified prenatal work-up flow for diagnosis. (2) Methods: A retrospective analysis was conducted on NIHF cases that were collected prospectively to explore the underlying etiologies according to a unified prenatal diagnosis work-up flow at Shanghai First Maternity and Infant Hospital between Jan 2016 and Dec 2019. The medical records for all NIHF cases were reviewed, and the causes of NIHF were classified as confirmed (diagnostic), suspected, or unknown. (3) Results: Prenatal and postnatal medical records for a total of 145 NIHF cases were reviewed, 48.3% (70/145) of the cases were identified to be with confirmed etiologies, and 10.3% (15/145) with suspected etiologies. Among 85 cases with confirmed or suspected etiologies, 44.7% were diagnosed with genetic disorders, 20% with chylothorax/chyloascites diagnosed postnatally, 12.9% with fetal structural anomalies, 12.9% with fetal anemia, 7% (6 cases) with fetal arrhythmia, and 2.3% (2 cases) with placenta chorioangioma. In cases with genetic disorders, 8 aneuploidies were detected by CMA, and 30 cases had single-gene disorders identified by ES (29/30) or targeted gene panel (1/30). There were still 41.4% cases (60/145) with unknown causes after this unified prenatal diagnostic work-up flow. (4) Conclusions: In the era of NGS, the causes of NIHF were identified in 58.6% of cases, with genetic disorders being the most common ones. NGS is helpful in determining the genetic etiology of NIHF when CMA results cannot explain NIHF, but 41.4% of cases were still with unknown causes under the unified prenatal diagnostic work-up flow in this single-center study.

Cost-Effectiveness of Exome Sequencing versus Targeted Gene Panels for Prenatal Diagnosis of Fetal Effusions and Non-Immune Hydrops Fetalis

BACKGROUND

Although exome sequencing has a greater overall diagnostic yield than targeted gene panels in the evaluation of nonimmune hydrops fetalis and fetal effusions, the cost-effectiveness of this approach is not known.

OBJECTIVE

This study aimed to evaluate the costs and outcomes of targeted gene panels vs exome sequencing for prenatally diagnosed nonimmune hydrops fetalis and fetal effusions when next-generation sequencing is pursued following nondiagnostic standard nonimmune hydrops fetalis evaluations, including karyotype or chromosomal microarray.

STUDY DESIGN

A decision-analytical model was designed using TreeAge Pro to compare 10 genetic testing strategies, including a single test only (RASopathy, metabolic, or nonimmune hydrops fetalis-targeted gene panel or exome sequencing), sequential testing (RASopathy panel followed by nonimmune hydrops fetalis panel, metabolic panel followed by nonimmune hydrops fetalis panel, RASopathy panel followed by exome sequencing, metabolic panel followed by exome sequencing, and nonimmune hydrops fetalis panel followed by exome sequencing), and no additional genetic testing. Our theoretical cohort included cases with normal karyotype and/or microarray and excluded cases of alloimmunization and congenital viral infections. As nonimmune hydrops fetalis and fetal effusions can present throughout gestation, whereas pregnancy management options vary depending on gestational age, outcomes were calculated for 3 time intervals: 10 to 18, 18 to 22, and >22 weeks of gestation. The primary outcome was incremental cost per quality-adjusted life year. Additional outcomes included termination of pregnancy, stillbirth, neonatal death, and neonates born with mild, moderate, and severe or profound disease phenotypes. The cost-effectiveness threshold was $100,000 per quality-adjusted life year.

RESULTS

Among women <18 weeks of gestation, exome sequencing alone was the dominant strategy associated with the lowest costs ($221 million) and the highest quality-adjusted life years (10,288). Strategies with exome sequencing alone or as a sequential test resulted in more terminations but fewer stillbirths, neonatal deaths (NNDs), and affected infants than strategies without exome sequencing. Among women between 18 and 22 weeks of gestation, exome sequencing alone was also associated with the lowest costs ($188 million) and the highest quality-adjusted life years (8734), and similar trends were observed in pregnancy outcomes. Among patients >22 weeks of gestations, when termination was not available, exome sequencing was associated with lower costs ($300 million) and the highest quality-adjusted life years (8492). Exome sequencing was cost-effective up to a cost per test of $50,451 at <18 weeks of gestation, $50,423 at 18 to 22 weeks of gestation, and $9530 at >22 weeks of gestation. Targeted genetic panels and exome sequencing were cost-effective strategies compared with no additional genetic testing.

CONCLUSION

For cases of nonimmune hydrops fetalis and fetal effusions with nondiagnostic karyotype or microarray, next-generation sequencing was cost-effective compared with a strategy without additional genetic testing. For those that undergo next-generation sequencing, exome sequencing was the cost-effective strategy compared with all other testing strategies using targeted gene panels, leading to lower costs and fewer adverse perinatal outcomes. Exome sequencing was cost-effective in a setting without the option for pregnancy termination. These data supported the routine use of exome sequencing when next-generation sequencing is pursued for establishing a genetic diagnosis underlying otherwise unexplained nonimmune hydrops fetalis and fetal effusions.

Current Perspectives of Prenatal Cell-free DNA Screening in Clinical Management of First-Trimester Septated Cystic Hygroma

First-trimester septated cystic hygroma occurs in approximately 1 in 268 pregnancies and has long been associated with a markedly increased risk of fetal aneuploidy and, among euploid fetuses, an increased risk of structural anomalies primarily affecting the cardiac and skeletal systems. Invasive prenatal diagnosis – chorionic villus sampling and/or amniocentesis – encompasses the time-honored clinical tools for the next step in management following prenatal sonographic diagnosis of first-trimester septated cystic hygroma. Currently, prenatal cell-free DNA (cfDNA) screening for fetal aneuploidy with select microdeletions is gradually replacing the considerably less sensitive, and labor-intensive combined first-trimester screening. These new technologies have opened potential new venues in the clinical management of this ominous late first-trimester sonographic diagnosis. Advances in cfDNA technologies are now permitting detection of chromosomal copy number variants (CNV) larger than 7Mb across genome and select serious single-gene disorders (mainly impacting skeletal and neurological development), affecting quality of life and may benefit from medical and/or surgical management. This commentary will address the available non-invasive prenatal screening technologies, which clearly enhance immediate genetic analysis modalities applicable in the presence of the complex sonographic finding of first-trimester septated cystic hygroma.

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.

Clinical Course and Outcome of Non-Immune Fetal Hydrops in Singleton Pregnancies

Nonimmune fetal hydrops is a condition defined by abnormal fluid accumulation in two or more body compartments. The aim is to evaluate factors associated with adverse outcome in diagnosed fetal hydrops and to investigate the aspects for the decision making in the case of termination of pregnancy. Therefore, a retrospective data analysis of pregnancies complicated by non-immune hydrops fetalis between 2004 and 2018 was performed in a single tertiary referral center. Of 361 pregnancies with diagnosed fetal hydrops, in 183 cases (50.7%), the parents decided to terminate the pregnancy. A strong relationship between etiology and termination of pregnancy was demonstrated, whereas the highest rates of termination of pregnancy were found if a chromosomal aberration was diagnosed. Of the remaining 178 cases, 51 cases (28.7%) had a miscarriage, 33 cases (18.5%) had an intrauterine fetal death, and 94 cases (52.8%) were live born, whereas 26 (27.7%) of these offspring died within the first week of life. The risk of an adverse outcome increased with lower gestational age at diagnosis (p < 0.001). A nuchal translucency thickness greater than 2.5 mm was associated with an adverse outcome (p < 0.01). Furthermore, pregnancies with adverse outcome had significantly more affected compartments (median: 3; IQR 2), compared with live born cases (median: 2; IQR 1; p < 0.01). In conclusion, adverse outcome in pregnancies with fetal hydrops was associated with a lower gestational age at diagnosis, nuchal translucency greater than 2.5 mm and a higher count of affected compartments. These results confirm that a precise clinical workup to identify the underlying etiology of non-immune fetal hydrops is essential for a better prognostic assessment and accurate counselling of parents.