Isolated Increased Nuchal Translucency in First Trimester Ultrasound Scan: Diagnostic Yield of Prenatal Microarray and Outcome of Pregnancy

Associations between genomic aberrations, increased nuchal translucency, and pregnancy outcomes: a comprehensive analysis of 2,272 singleton pregnancies in women under 35

Objectives

Regarding increased nuchal translucency (NT), the cutoff values used are heterogeneous in clinical practice, this study aims to assess the efficacy of prenatal detection for chromosomal abnormalities and pregnancy outcomes in fetuses with varying NT thicknesses, in order to provide data that supports informed prenatal diagnosis and genetic counseling for such cases.

Methods

We included 2,272 pregnant women under 35 with singleton pregnancies who underwent invasive prenatal diagnosis between 2014 and 2022. The cohort comprised 2,010 fetuses with increased NT (≥2.5 mm) and 262 fetuses with normal NT but exhibiting a single soft marker. Prenatal diagnoses were supported by chromosomal microarray (CMA) and copy number variation sequencing (CNV-seq) analyses.

Results

The detection rates of numerical chromosomal abnormalities were 15.4% (309/2,010) and 17.3% (297/1,717) in the NT ≥2.5 and ≥ 3.0 groups, respectively. Pathogenic/likely pathogenic CNV incidence increased with NT thickness (χ2 = 8.60, p < 0.05), peaking at 8.7% (22/254) in the NT 4.5-5.4 mm group. Structural defects were found in 18.4% of fetuses with NT values between 2.5 mm and 2.9 mm. Chromosomal abnormality rates in the isolated increased NT groups of 2.5-2.9 mm and 3.0-3.4 mm were 6.7% (16/239) and 10.0% (47/470), respectively, with no statistical significance (χ2 = 2.14, p > 0.05). Fetuses with NT thickness between 2.5 and 2.9 mm combined with the presence of soft markers or non-lethal structural abnormalities exhibited a significantly higher chromosomal abnormality risk (19.0%) compared to fetuses with isolated increased NT ranging from 3.5 to 4.4 mm (13.0%). Pregnancy termination rates increased with NT thickness (χ2 = 435.18, p < 0.0001), ranging from 12.0% (30/249) in the NT 2.5-2.9 mm group to 87.0% (141/162) in the NT ≥ 6.5 mm group.

Conclusion

CMA or CNV-seq exhibited good performance in identifying genomic aberrations in pregnancies with increased NT thickness. NT ranging from 2.5 mm to 2.9 mm elevated the risk of fetal chromosomal abnormalities, particularly when combined with other soft markers.

Enhancing Fetal Anomaly Detection in Ultrasonography Images: A Review of Machine Learning-Based Approaches

Fetal development is a critical phase in prenatal care, demanding the timely identification of anomalies in ultrasound images to safeguard the well-being of both the unborn child and the mother. Medical imaging has played a pivotal role in detecting fetal abnormalities and malformations. However, despite significant advances in ultrasound technology, the accurate identification of irregularities in prenatal images continues to pose considerable challenges, often necessitating substantial time and expertise from medical professionals. In this review, we go through recent developments in machine learning (ML) methods applied to fetal ultrasound images. Specifically, we focus on a range of ML algorithms employed in the context of fetal ultrasound, encompassing tasks such as image classification, object recognition, and segmentation. We highlight how these innovative approaches can enhance ultrasound-based fetal anomaly detection and provide insights for future research and clinical implementations. Furthermore, we emphasize the need for further research in this domain where future investigations can contribute to more effective ultrasound-based fetal anomaly detection.

Prenatal whole-exome sequencing in fetuses with increased nuchal translucency

BACKGROUND

Increased nuchal translucency (NT) is associated with an increased risk for genetic disorders. The aim of this study was to investigate the value of whole-exome sequencing (WES) in detecting genetic abnormalities for fetuses with isolated first-trimester increased NT.

METHODS

After the exclusion of aneuploidies and pathogenic copy number variants (CNVs) by quantitative fluorescent polymerase chain reaction (QF-PCR) and chromosomal microarray analysis (CMA), WES was performed on 63 fetuses with isolated first-trimester increased NT (≥3.5 mm).

RESULTS

Overall, WES yielded a 4.8% (3/63) diagnostic rate for fetuses with isolated increased NT. Pathogenic variants were identified in 37.5% (3/8) fetuses that developed additional structural anomalies later in gestation, and no pathogenic variants were detected in increased NT that resolved or remained isolated throughout the pregnancy.

CONCLUSION

This study provides powerful evidence to offer prenatal WES for increased NT only when additional abnormalities are present. Early detailed ultrasound to detect emerging anomalies can help physicians offer prenatal WES to fetuses with a greater likelihood of diagnosis.

Fetal left ventricular myocardial performance index measured at 11-14 weeks of gestation in fetuses with an increased nuchal translucency

OBJECTIVE

This study aimed to evaluate the effect of an increase in nuchal translucency (NT) thickness on the myocardial performance index (MPI) in fetuses without cardiac anomaly in the first trimester and to determine whether a difference in MPI between those with and without trisomy 21 in these fetuses could be determined.

METHODS

The study group consisted of 53 pregnancies complicated with increased NT thickness without any associated structural anomalies. Forty-six gestational age-matched pregnant women whose fetuses had normal NT thickness were enrolled as the control group.

RESULTS

In the increased NT thickness group, the mean isovolumetric relaxation time (IRT) value (0.050 ± 0.011 s) was significantly higher and the mean ejection time (ET) value (0.149 ± 0.010 s) was significantly lower than those values in the normal NT thickness group (0.045 ± 0.005 and 0.155 ± 0.009 s, p = 0.023 and p = 0.009, respectively). We found a significantly higher mean left MPI value in the increased NT thickness group (0.574 ± 0.153) versus the normal NT thickness group (0.487 ± 0.107, p < 0.001). Within the increased NT thickness group, the mean left MPI value was similar in the fetuses with normal karyotype and those with trisomy 21 (p = 0.419).

CONCLUSION

We demonstrated a significantly greater mean MPI value in the increased NT thickness group than in the normal NT thickness group. Within the increased NT thickness group, no differences in the left MPI value in the fetuses with normal karyotype and the fetuses with trisomy 21 were found.

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.

Application of chromosome microarray analysis and karyotyping in diagnostic assessment of abnormal Down syndrome screening results

Background

Down syndrome (DS) is the most common congenital cause of intellectual disability and also leads to numerous metabolic and structural problems. This study aims to explore the application value of chromosomal microarray analysis (CMA) and karyotyping in prenatal diagnosis for pregnant women with abnormal DS screening results.

Methods

The study recruited 1452 pregnant women with abnormal DS screening results including 493 with an enlarged nuchal translucency thickness (NT ≥ 2.5 mm) and 959 with an abnormal second-trimester maternal serum biomarker screening results. They underwent amniocentesis to obtain amniotic fluid for CMA and karyotyping.

Results

CMA identified 74/1452 abnormal results, which was more efficient than karyotyping (51/1452, P < 0.05.) CMA is equivalent to traditional karyotyping for identifying aneuploidies. Compared to karyotyping CMA identified 1.90% more copy number variants (CNVs) ranging from 159Kb to 6496Kb. However, 34.4% of them were recurrent pathogenic CNVs associated with risk of neurodevelopmental disorders. CMA identified 13 variants of uncertain significance (VUS) results and 1 maternal uniparental disomy (UPD) of chromosome 7. Karyotyping identified 3 mosaic sex chromosome aneuploidy and 4 balanced translocation which could not be identified by CMA. In enlarged NT group, karyotyping identified 80.9% abnormal results while in serum screening group karyotyping identified 35.7%. However, the incidence of pathogenic/likely pathogenic (P/LP) CNVs was nearly the same in both groups. That was because aneuploidies and gross duplication/deletion were previously screened out by NT scan.

Conclusions

CMA and karyotyping have both advantages and disadvantages in prenatal diagnosis of pregnant women with abnormal DS screening results. However, there was not enough evidence to support routine CMA in pregnant women with abnormal DS screening results.

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.