OBJECTIVE:To evaluate postnatal medical genetic reassessment and reinterpretation of prenatal exome sequencing (pES) in liveborn children with prenatally identified structural anomalies and nondiagnostic prenatal genetic testing. METHOD:We performed a retrospective chart review of 61 liveborn children with fetal structural anomalies who had nondiagnostic chromosomal studies and pES at a tertiary care center in British Columbia, Canada (2016-2022). We assessed postnatal medical genetics reassessment, clinical drivers of reassessment, and outcomes of selective pES reinterpretation. RESULTS:Postnatal medical genetics reassessment occurred in 41% (25/61) of children. Most reassessments occurred in the neonatal intensive care unit within the first week of life (68%, 17/25) and were prompted by postnatal phenotype modifications in 44% (11/25). Additional clinical drivers prompting reassessment included prenatally identified variants of uncertain significance and prenatal phenotypes of multisystem structural anomalies or unexplained hydrops. Of the children reassessed postnatally, 44% (11/25) underwent pES reinterpretation. Explanatory genetic diagnoses following reassessment and pES reinterpretation were made in 27% (3/11), representing 12% (3/25) of those reassessed and 5% (3/61) of the cohort. One additional postnatal genetic diagnosis was made, which explained a portion of the postnatal phenotype but was not considered explanatory for the prenatal findings. CONCLUSION:Postnatal pES reinterpretation identified genetic diagnoses in carefully selected cases following medical genetics reassessment of children with nondiagnostic prenatal testing for fetal structural anomalies, supporting a structured, clinically guided approach to postnatal follow-up.
OBJECTIVE:Trisomy 21 (T21) is associated with various neurological impairments. However, the mechanisms of fetal brain development in T21 and their impact on neurodevelopmental outcomes remain unclear, limiting prenatal counseling. Therefore, this study aims to assess neuropathological changes in fetuses with T21 and the associated neurodevelopmental outcome. METHOD:This was a case-control study comparing brain patterns in neurosonography and MRI of fetuses with T21 to healthy controls. Additionally, neurodevelopmental outcome was assessed prospectively. Thereby, an outcome score was calculated to identify brain patterns linked to unfavorable neurodevelopmental outcomes. RESULTS:108 fetuses were included consisting of 54 fetuses with T21 and 54 controls. In the study group, significantly more fetal brain abnormalities were found compared to the control group (p < 0.001). Brain abnormalities in T21 most commonly included ventriculomegaly (24.1%), cerebellar hypoplasia (22.2%) and widening of subarachnoid fluid spaces (20.4%). Although the neurodevelopmental score showed no significant differences based on the presence of brain abnormalities, fetuses with widened subarachnoid fluid spaces or cerebellar hypoplasia were solely associated with an unfavorable outcome score. CONCLUSION:Fetuses with T21 show significantly more brain abnormalities compared with healthy controls, which should be considered for prenatal counseling. Some specific brain abnormalities were demonstrated only in the group with poorer neurodevelopmental outcomes, such as cerebellar hypoplasia and widened subarachnoid fluid spaces. However, the exploratory nature of the analysis must be considered, and additional studies are highly needed.
OBJECTIVE:Maternal sirolimus therapy has emerged as a potential prenatal treatment for extensive fetal lymphatic malformations, particularly when associated with the risk of neonatal airway compromise. Data on prenatal indications, pharmacokinetics, and outcomes remain limited. We aimed to describe patient selection, treatment management, maternal and fetal safety, and early outcomes. METHODS:Between December 2023 and May 2025, 15 fetuses with extensive cystic or mixed vascular anomalies suggestive of lymphatic malformations were referred to a national reference center. Prenatal ultrasound and fetal magnetic resonance imaging were performed. After maternal evaluation and informed consent, sirolimus was administered with weekly dose adjustments based on maternal trough levels. Tolerance, drug concentrations at delivery, obstetric outcomes, and neonatal evolution were assessed. Decrease in lesion extent was assessed using a semi-quantitative 0-4 imaging scale. RESULTS:Six fetuses received therapy after the exclusion of nine cases. Treatment began between 24 and over 30 weeks' gestation. Maternal adverse effects were mild. Transplacental drug transfer was observed with variable maternal-fetal ratios. Mean gestational age at birth was 38.1 weeks. Partial or marked lesion regression occurred in five newborns. CONCLUSIONS:Maternal sirolimus therapy appears feasible and well tolerated for extensive fetal lymphatic malformations, demonstrating transplacental transfer and encouraging early perinatal outcomes in carefully selected pregnancies overall.
OBJECTIVES:To describe a cohort of fetuses with abnormal prenatal findings in whom exome sequencing (ES) identified genetic diagnoses that refined prognostic assessment and reduced prognostic uncertainty. METHODS:We retrospectively reviewed all fetal ES studies performed at our center between 2017 and 2025 for structural or biochemical abnormalities. Cases with a definitive molecular diagnosis were identified, and those with predicted mild, isolated, transient, or treatable phenotypes were classified as having comparatively favorable prognostic implications. Clinical findings and expected postnatal outcomes were analyzed. RESULTS:Among 1692 fetuses undergoing ES, a molecular diagnosis was identified in 291 (17%). Of these, five cases (∼2%) were considered reassuring: isolated postaxial polydactyly due to a GLI1 variant; X-linked ichthyosis (STS) in a fetus with low estriol; isolated situs inversus; CFAP52-related situs inversus totalis; and MAGED2-associated transient antenatal Bartter syndrome. In all cases, ES refined prognosis and reduced the likelihood of severe syndromic conditions, enabling clearer counseling. CONCLUSIONS:Beyond detecting severe disorders, ES may help distinguish mild or manageable conditions from complex syndromes. In selected cases, it provides meaningful reassurance, reduces uncertainty, and supports informed prenatal decision-making.
OBJECTIVE:To present the prenatal sonographic features, genomic findings, and pregnancy outcomes of fetuses with biallelic pathogenic RNU4ATAC variants linked to microcephalic osteodysplastic primordial dwarfism type I (MOPD1). METHODS:This retrospective case series includes five prenatal cases with MOPD1. Diagnoses were established by prenatal ultrasound and genetic testing. Genome sequencing (GS) or targeted exome sequencing (ES) detected the variants either prenatally or after termination of pregnancy (TOP). Clinical data including parental demographics, ultrasound findings, and pregnancy outcomes were collected. RESULTS:All fetuses presented with consistent anomalies on ultrasound including intrauterine growth restriction (IUGR), microcephaly, agenesis of the corpus callosum (ACC), intracranial cysts, lissencephaly, and micrognathia. IUGR was the earliest anomaly detected in all five cases. Prenatal ultrasound findings suggestive of skeletal dysplasia were identified in one case. All cases carried biallelic pathogenic RNU4ATAC variants associated with MOPD1. TOP was chosen in four cases. One fetus was delivered at 39 + 1 weeks with genetic diagnosis confirmed at 27 weeks. CONCLUSION:IUGR, microcephaly and ACC can be detected in fetuses with MOPD1 at around 18 weeks of gestation. Interestingly, skeletal dysplasia was not a consistent prenatal finding. Variants in the non-coding RNU4ATAC gene need to be detected by GS or targeted approaches beyond standard ES.
OBJECTIVE:Uniparental disomy (UPD), particularly heterodisomy (hUPD), is an underdiagnosed etiology in cases of fetal growth restriction (FGR) and discordant noninvasive prenatal testing (NIPT). Because conventional absence-of-heterozygosity (AOH) analysis frequently misses hUPDs, we aimed to validate a systematic Mendelian inheritance error (MIE) analysis pipeline for trio exome sequencing (trio-ES) to resolve ambiguous prenatal findings. METHOD:A two-stage study analyzed 1948 parent-offspring trios (postnatal and prenatal samples). A retrospective cohort (n = 992) established and validated a quantitative biparental inheritance percentage (BPI%) threshold. This workflow was prospectively applied (n = 956) to evaluate clinical utility, focusing on discordant NIPT and unexplained fetal growth restriction (FGR). Orthogonal analysis of methylation or short-tandem repeats (STR) were used to confirm identified UPD. RESULTS:Utilizing a BPI% < 0.7 threshold, the pipeline identified 12 clinically significant UPD events. Crucially, 25% (3/12) were hUPDs missed by standard AOH analysis of exome. Prenatally, the pipeline resolved 57.1% (4/7; 95% CI: 18.4%-90.1%) of discordant NIPT cases, inferring trisomy rescue and confined placental mosaicism that explained the associated FGR. Postnatally, it unmasked 8 UPD events associated with imprinting disorders for pediatric cases. CONCLUSION:MIE analysis of existing trio-ES data effectively captures hUPDs missed by conventional AOH analysis. Routine integration of this pipeline resolves discordant NIPT results, explains FGR, and enables comprehensive UPD detection.
OBJECTIVE:Absence of heterozygosity (AOH) is a clinically significant genomic feature often associated with uniparental disomy and parental consanguinity in the prenatal settings. Chromosomal microarray analysis (CMA) is commonly used for AOH detection, while sequencing-based approaches may provide complementary genomic information within a single assay. This study evaluated the performance of medium-coverage whole-genome sequencing (CNV-plus) for the detection of prenatal AOH. METHODS:We analyzed 45 prenatal samples (35-CMA-positive, 10-CMA-negative). Concordance between CNV-plus and CMA was assessed at regional, genome-wide, and sample levels, with particular emphasis on the effect of AOH segment size. RESULTS:CNV-plus detected 56 AOH regions compared with 65 by CMA, yielding 68 matched segments. Segment-level sensitivity was 86.8%, showing clear size dependence: 53.3% for 5-10 Mb regions and 96.2% for regions > 10 Mb. Genome-wide overlap was high (global Jaccard index = 0.871), although boundary resolution differed between methods. At the sample level, CNV-plus achieved 97.1% sensitivity and 100% specificity, with no significant difference from CMA. CONCLUSIONS:CNV-plus demonstrates good concordance with CMA for detecting larger AOH regions in prenatal samples and may serve as a complementary approach when considering its size-dependent performance.
Red blood cell (RBC) alloimmunization remains a relevant cause of hemolytic disease of the fetus and newborn (HDFN). Although RhD immunization has significantly decreased since the implementation of systematic prophylaxis, it is still the main cause of alloimmunization in pregnancy. Clinically significant non-RhD alloantibodies, particularly those of the Rh (c, C, E), Kell, Kidd, Duffy, and MNS systems, are associated with variable risk of fetal anemia and account for an increasing proportion of alloimmunized pregnancies requiring specialized prenatal care. Most diagnostic algorithms and management protocols are based on evidence derived from RhD alloimmunization. Although these frameworks are often extrapolated to other alloantibodies, important differences exist regarding antibody titration and critical thresholds, the diagnostic accuracy of non-invasive fetal antigen genotyping, and the risk and timing of fetal and neonatal interventions. These differences underscore the need for antibody-specific considerations in the prenatal diagnosis and management of non-RhD alloimmunization. Though advances in non-invasive diagnostic techniques have improved risk stratification and optimized prenatal management, individualized care pathways in alloimmunized pregnancies are needed. This review will focus on the current strategies for prenatal diagnosis and risk assessment in pregnancies complicated by non-RhD red cell alloimmunization.
OBJECTIVE:Non-invasive prenatal testing (NIPT) identifies fetal chromosomal abnormalities by sequencing cell-free fetal DNA (cffDNA). Recent studies suggest the prediction of viral sequences from NIPT data, but current methods lack cost-effectiveness for routine use. This study develops a straightforward workflow to investigate potential viral signatures in pregnant women using NIPT data from 888 Iranian participants. METHOD:Two bioinformatic workflows were compared for predicting viral reads: the traditional method involved mapping reads to the human genome, followed by mapping unmapped reads to viral references, and a direct mapping approach to viral genomes, as proposed in this research. RESULTS:While maintaining reproducibility comparable to the conventional method, the proposed workflow minimizes computational complexity and time usage for data processing. Ultimately, this analysis suggested viral DNA in 24.2% of samples, encompassing 29 distinct species, implying the diversity of the maternal virome. CONCLUSION:This study presents a computationally efficient workflow for the in silico prediction of viral-like sequences from routine NIPT data. Further experimental validation is essential to verify the presence, viability, or clinical relevance of these sequences.
OBJECTIVE:Quantitative assessment of the impact of cytomegalovirus (CMV) infection on fetal brain development beyond conventional imaging remains limited. We aimed to quantify cortical gyrification and brain volumes in CMV-exposed fetuses, compare groups with varying severities of conventional MRI findings, and evaluate postnatal outcomes. METHOD:This retrospective study included 82 singleton pregnancies following maternal CMV infection. Fetuses were grouped by CMV infection status and conventional MRI findings. Automated tools quantified cerebral gyrification and supratentorial, infratentorial and lateral ventricle volumes. Postnatal hearing and neurodevelopmental outcomes were assessed at follow-up. RESULTS:CMV-infected fetuses (n = 67) showed reduced cerebral gyrification compared with uninfected controls (n = 15). This reduction was observed across fetuses with gross (n = 10), subtle (n = 19), and even normal (n = 38) MRI findings. Infected fetuses with gross abnormalities also showed reduced infratentorial volume compared with infected fetuses with normal MRI and controls. Follow-up was available in 42 cases and indicated that most children developed normally. However, eight children developed mild-to-moderate neurodevelopmental difficulties, four of whom also had sensorineural hearing loss, including cases with normal or subtle prenatal imaging. CONCLUSION:Quantitative analysis of routine fetal MRI reveals alterations in brain development in CMV-infected fetuses, including those with normal conventional imaging, and may improve the identification of fetuses at risk for adverse outcomes.
OBJECTIVE:To describe diagnostic trajectories and parental decision-making following increased first-trimester nuchal translucency (NT), according to NT thickness. METHOD:This 12-year retrospective cohort study was conducted at a French tertiary Prenatal Diagnosis and Fetal Medicine Center and included 316 singleton pregnancies with first-trimester NT ≥ 3.5 mm, with or without structural anomalies. RESULTS:Termination of pregnancy occurred in 180/316 pregnancies (57.0%), while 91/316 (28.8%) resulted in live birth without pathology. TOP without prior invasive prenatal testing increased from 7.4% in the 3.5-< 5.0 mm group to 35.0% in the ≥ 6.5 mm group. Invasive prenatal testing was performed in 248 pregnancies. Among 137 pregnancies with an abnormal genetic result and known outcome, 12 (8.8%) were continued. Structural ultrasound assessment was performed in 111 pregnancies; 17/29 (58.6%) with abnormal findings were continued. Among 51 pregnancies that continued after normal genetic testing and normal structural ultrasound, 42 (82.4%) resulted in live birth without pathology at the last follow-up, including 3/8 (37.5%) with NT ≥ 6.5 mm. CONCLUSION:Parental decisions and outcomes varied with NT thickness. Integrating NT measurements with sequential genetic and ultrasound findings may support individualized prenatal counseling.
OBJECTIVE(S):Fetal pleural effusion is a rare condition that may significantly impact fetal and neonatal outcomes. Currently, no universal standardized approach exists for diagnosing and managing primary fetal pleural effusions. This study aimed to develop structured, expert-based clinical guidelines for the diagnosis, monitoring, management, and follow-up care of primary fetal pleural effusion. METHODS:A Delphi method was employed to achieve consensus among an international panel of experts in fetal medicine. Experts were selected based on their clinical expertise, affiliations, and relevant publications. A three-round anonymous electronic survey was sent to the full panel. In the initial two rounds, participants rated each statement on a Likert scale (1-5) and provided suggestions for modifications. Statements with a median score of five and no suggested changes were accepted as consensus. Statements with a median score below four were rejected. Statements scoring a median of four were revised according to suggestions and reconsidered in the subsequent round. In the final round, participants indicated their agreement or disagreement with the remaining statements. Consensus was defined as agreement from more than 70% of participants with no suggestions for further changes. RESULTS:A total of 101 expert clinicians accepted the invitation and completed the first round with 73 (72%) completing all three rounds. Consensus statements were achieved on aspects of diagnosis, monitoring, intervention, post-intervention management, and delivery. Key recommendations concerning the diagnosis of primary fetal pleural effusion include the use of ultrasound as the primary modality for identifying fetal pleural effusion and excluding secondary causes through detailed genetic, infectious, and metabolic evaluations. Management strategies emphasized thoracoamniotic shunting as the preferred intervention in hydropic fetuses with primary pleural effusion. Experts reached consensus that shunt placement could be offered as early as 16 weeks. No consensus was reached for isolated effusion without hydrops, as management was considered case-dependent. The importance of ultrasonographic monitoring of fetal status at least weekly post-intervention was strongly endorsed. CONCLUSION(S):The Delphi method facilitated the development of a consensus-based protocol for diagnosing and managing primary fetal pleural effusion. These standardized guidelines are intended to enhance clinical practice across various settings, improve perinatal outcomes, and serve as a foundation for future research for this high-risk fetal condition.
OBJECTIVE:To evaluate the clinical characteristics, genomic landscape, and perinatal outcomes of fetal polydactyly using combined copy number variation sequencing (CNV-seq) and trio-exome sequencing (trio-ES). METHODS:This retrospective cohort study included 44 prenatally confirmed fetuses with polydactyly. Cases were stratified into isolated (n = 21) and non-isolated (n = 23) groups. Polydactyly was further subclassified according to anatomical distribution, laterality, and duplication axis. Genetic etiology was investigated using CNV-seq and trio-ES, and pregnancy outcomes were ascertained through clinical follow-up. RESULTS:The overall genetic diagnostic yield was 36.4% (16/44), comprising aneuploidies (n = 6), one pathogenic CNV and monogenic disorders (n = 9). Causative variants were identified in NEK1, EVC2, BBS4, GLI3, TBX3, MYCN, and KIAA0825, with one incidental finding in PIK3CD. The diagnostic yield was significantly higher in the non-isolated group than in the isolated group (60.9% vs. 9.5%, p < 0.001). Specific anatomical features were associated with markedly increased genetic burden, including concurrent involvement of both upper and lower limbs (100%), bilateral presentation (64.7% vs. 18.5% for unilateral; p < 0.01), and postaxial polydactyly (PAP) compared with preaxial polydactyly (PPD) (65.0% vs. 12.5%; p < 0.001). Pregnancy outcomes differed substantially between phenotypic subgroups, with a live birth rate of 100% in isolated cases versus 34.8% in non-isolated cases (p < 0.001). CONCLUSION:Fetal polydactyly exhibits profound genetic and phenotypic heterogeneity. Although non-isolated, multi-limb, bilateral, and postaxial presentations are strong predictors of underlying chromosomal or monogenic disorders, apparently isolated cases still carry a clinically relevant genetic risk. The integration of detailed prenatal sonographic phenotyping with CNV-seq and trio-ES improves diagnostic precision, facilitates prognostic assessment, and informs prenatal counseling and long-term postnatal surveillance.
OBJECTIVES:Partial gene duplications (PGDups) are a significant contributor to genetic disease. The precise genomic location and structure of PGDups are often unresolved using conventional methods, so prenatal diagnosis for PGDups is challenging, especially without ultrasound abnormalities. METHODS:We retrospectively applied structural variation sequencing (SVseq) to 26 amniotic fluid samples with PGDups initially identified by chromosomal microarray or sequencing. SVseq utilized mate-pair library construction and high-throughput sequencing to map PGDup structures. Pathogenicity was classified using ACMG guidelines, followed by postnatal phenotypic follow-up. RESULTS:SVseq deciphered the PGDup structure for all twenty-six cases. Twenty-two (84.62%) were tandem duplications (TDs), three (11.54%) chromosomal complex rearrangements (CCRs), and one (3.85%) had no duplication. Among twenty-two TDs, thirteen were extragenic (TDEG), preserving gene integrity, and were classified as benign or variants of uncertain significance (VUS). Nine were intragenic (TDIG), disrupting gene structure, and were rated pathogenic or likely pathogenic (P/LP) or VUS. Postnatal follow-up revealed obvious abnormal phenotypes in only two TDIG cases (one inherited and one de novo). CONCLUSION:SVseq effectively resolves PGDup location and structure, allowing confident pathogenicity assessment and clear genotype-phenotype correlation. SVseq is a robust method for prenatal PGDup evaluation that could be adopted in diagnostic protocols to improve clinical outcomes.
OBJECTIVE:To review the published literature on prenatal findings of COL2A1-related SEDC, summarizing reported imaging and molecular variants, and to describe two additional prenatal cases evaluated at a tertiary referral center. METHOD:A narrative review with a systematic search strategy was conducted to analyze prenatal imaging findings, gestational age at detection, and molecular diagnoses in cases of COL2A1-related SEDC. Clinical and molecular description of two additional fetal cases with postnatal molecular confirmation were also included. RESULTS:Gestational age at initial detection ranged from 11 to 28 weeks. Five reported cases occurred in a familial setting, while two were initially considered sporadic. In several cases, complementary imaging modalities were required to better characterize vertebral and ossification defects. A clear genotype-phenotype correlation could not be reliably established; no specific molecular pattern reliably predicted the severity of prenatal imaging findings or perinatal outcomes. CONCLUSION:Our findings highlight the nonspecific nature of prenatal manifestations in COL2A1-related SEDC, which despite being largely consistent across cases do not allow for a specific diagnosis without molecular confirmation or a known family history. These challenges underscore the need for a comprehensive diagnostic strategy that integrates detailed imaging, molecular genetic testing, and close collaboration within a multidisciplinary team.
