Abnormal nuchal translucency: residual risk with normal cell-free DNA screening

Is Nuchal Translucency of 3.0-3.4 mm an Indication for cfDNA Testing or Microarray? - A Multicenter Retrospective Clinical Cohort Study

INTRODUCTION

This study aimed to evaluate the occurrence of clinically relevant (sub)microscopic chromosomal aberrations in fetuses with the nuchal translucency (NT) range from 3.0 to 3.4 mm, which would be potentially missed by cfDNA testing.

METHODS

A retrospective data analysis of 271 fetuses with NT between 3.0 and 3.4 mm and increased first trimester combined test (CT) risk in five cohorts of pregnant women referred for invasive testing and chromosomal microarray was performed.

RESULTS

A chromosomal aberration was identified in 18.8% fetuses (1:5; 51/271). In 15% (41/271) of cases, trisomy 21, 18, or 13 were found. In 0.7% (2/271) of cases, sex chromosome aneuploidy was found. In 1.1% (3/271) of cases, CNV >10 Mb was detected, which would potentially also be detected by genome-wide cfDNA testing. The residual risk for missing a submicroscopic chromosome aberration in the presented cohorts is 1.8% (1:54; 5/271).

CONCLUSION

Our results indicate that a significant number of fetuses with increased CT risk and presenting NT of 3.0-3.4 mm carry a clinically relevant chromosomal abnormality other than common trisomy. Invasive testing should be offered, and counseling on NIPT should include the test limitations that may result in NIPT false-negative results in a substantial percentage of fetuses.

Ultrasonographic Fetal Nuchal Translucency Measurements and Cytogenetic Outcomes

Importance

Ultrasonographic measurement of fetal nuchal translucency is used in prenatal screening for trisomies 21 and 18 and other conditions. A cutoff of 3.5 mm or greater is commonly used to offer follow-up investigations, such as prenatal cell-free DNA (cfDNA) screening or cytogenetic testing. Recent studies showed a possible association with chromosomal anomalies for levels less than 3.5 mm, but extant evidence has limitations.

Objective

To evaluate the association between different nuchal translucency measurements and cytogenetic outcomes on a population level.

Design, Setting, and Participants

This population-based retrospective cohort study used data from the Better Outcomes Registry & Network, the perinatal registry for Ontario, Canada. All singleton pregnancies with an estimated date of delivery from September 1, 2016, to March 31, 2021, were included. Data were analyzed from March 17 to August 14, 2023.

Exposures

Nuchal translucency measurements were identified through multiple-marker screening results.

Main Outcomes and Measures

Chromosomal anomalies were identified through all Ontario laboratory-generated prenatal and postnatal cytogenetic tests. Cytogenetic testing results, supplemented with information from cfDNA screening and clinical examination at birth, were used to identify pregnancies without chromosomal anomalies. Multivariable modified Poisson regression with robust variance estimation and adjustment for gestational age was used to compare cytogenetic outcomes for pregnancies with varying nuchal translucency measurement categories and a reference group with nuchal translucency less than 2.0 mm.

Results

Of 414 268 pregnancies included in the study (mean [SD] maternal age at estimated delivery date, 31.5 [4.7] years), 359 807 (86.9%) had a nuchal translucency less than 2.0 mm; the prevalence of chromosomal anomalies in this group was 0.5%. An increased risk of chromosomal anomalies was associated with increasing nuchal translucency measurements, with an adjusted risk ratio (ARR) of 20.33 (95% CI, 17.58-23.52) and adjusted risk difference (ARD) of 9.94% (95% CI, 8.49%-11.39%) for pregnancies with measurements of 3.0 to less than 3.5 mm. The ARR was 4.97 (95% CI, 3.45-7.17) and the ARD was 1.40% (95% CI, 0.77%-2.04%) when restricted to chromosomal anomalies beyond the commonly screened aneuploidies (excluding trisomies 21, 18, and 13 and sex chromosome aneuploidies).

Conclusions and Relevance

In this cohort study of 414 268 singleton pregnancies, those with nuchal translucency measurements less than 2.0 mm were at the lowest risk of chromosomal anomalies. Risk increased with increasing measurements, including measurements less than 3.5 mm and anomalies not routinely screened by many prenatal genetic screening programs.

A Novel Framework for Abnormal Risk Classification over Fetal Nuchal Translucency Using Adaptive Stochastic Gradient Descent Algorithm

In most maternity hospitals, an ultrasound scan in the mid-trimester is now a standard element of antenatal care. More fetal abnormalities are being detected in scans as technology advances and ability improves. Fetal anomalies are developmental abnormalities in a fetus that arise during pregnancy, birth defects and congenital abnormalities are related terms. Fetal abnormalities have been commonly observed in industrialized countries over the previous few decades. Three out of every 1000 pregnant mothers suffer a fetal anomaly. This research work proposes an Adaptive Stochastic Gradient Descent Algorithm to evaluate the risk of fetal abnormality. Findings of this work suggest that proposed innovative method can successfully classify the anomalies linked with nuchal translucency thickening. Parameters such an accuracy, recall, precision, and F1-score are analyzed. The accuracy achieved through the suggested technique is 98.642.%.

Application of expanded noninvasive prenatal test in prenatal diagnosis of fetuses with increased nuchal translucency

OBJECTIVES

To investigate the efficiency of the upgraded noninvasive prenatal test (NIPT-Plus) in fetuses with increased nuchal translucency (NT).

METHODS

Fetuses with an increased NT at or above 2.5 mm were selected for prenatal diagnosis. Amniotic fluid was collected from all cases for karyotype analysis and copy number variation sequencing (CNV-seq), and cell-free fetal DNA (cfDNA) in maternal blood was tested using Noninvasive Prenatal Test (NIPT-Plus) before amniocentesis in some cases. The results of amniocentesis with different NT thicknesses were analyzed and compared with those of NIPT-Plus.

RESULTS

A total of 125 eligible patients were divided into group A (2.5 mm ≤ NT < 3.0 mm) and group B (NT ≥ 3.0 mm). In group A, the detection rate of chromosomal aneuploidy and pathogenic copy number variation (CNV) was 10.6% and 6.4%, respectively. The total chromosome abnormality rate in group B (34.7%) was significantly higher than that in group A (17%). In 72 patients who underwent NIPT-Plus and amniocentesis, chromosomal aneuploidy accounted for 80.8% of the total chromosomal abnormalities. Among 21 cases of chromosomal aneuploidy, NIPT-Plus detected 20 cases. The sensitivity and specificity of NIPT-Plus toward aneuploidy detection were 95.2% and 100%, respectively. Among the five cases of pathogenic CNV, only two were detected using NIPT-Plus.

CONCLUSION

NIPT-plus is recommended as the first choice for fetal diagnosis in pregnant women with 2.5 mm ≤ NT < 3.0 mm who do not accept invasive prenatal diagnosis. When NT ≥ 3.0 mm and NIPT-Plus detects chromosomal aneuploidy, a rapid prenatal diagnosis can be performed through amniocentesis. In cases where NIPT-Plus yields negative results, amniocentesis still needs to be performed to detect chromosome microdeletions/duplications in order to avoid a missed diagnosis.

Impact of cell-free fetal DNA on early invasive prenatal diagnosis at a Chinese reference maternal medicine center

Purpose: The aim of this study is to evaluate the impact of the utility of maternal cell-free DNA (cfDNA) on the number of chorionic villus sampling (CVS) at a mainland Chinese maternal hospital.Methods: This was a retrospective cohort study conducted in consecutive singleton pregnancies that underwent CVS between the 11th and 14th gestational weeks at a Chinese maternal hospital during a nine-year period. The indications, complications and prenatal diagnosis results were evaluated.Results: This study consisted of 5108 CVS procedures, including 2000 performed for fetal karyotyping, and 3108 performed for fetal single-gene genotyping. During the period with the introduction of cfDNA, the proportion of the number of CVS procedures for the indication of positive serum screening declined significantly, and abnormal ultrasound was the main indication for CVS performed for fetal karyotyping. Thalassemia was always the main indication for CVS, accounting for 50.5% of all CVS cases.Conclusions: cfDNA has changed the spectrum of CVS indications. CVS is now the invasive procedure performed for patients with a fetus having a very high risk of fetal genetic defects, including fetuses having major abnormal ultrasound or having a risk of single-gene disorder inherited from their parents.

Nuchal translucency of 3.0-3.4 mm an indication for NIPT or microarray? Cohort analysis and literature review

Introduction

Currently fetal nuchal translucency (NT) ≥3.5 mm is an indication for invasive testing often followed by chromosomal microarray. The aim of this study was to assess the risks for chromosomal aberrations in fetuses with an NT 3.0‐3.4 mm, to determine whether invasive prenatal testing would be relevant in these cases and to assess the residual risks in fetuses with normal non‐invasive prenatal test (NIPT) results.

Material and methods

A retrospective study and meta‐analysis of literature cases with NT between 3.0 and 3.4 mm and 2 cohorts of pregnant women referred for invasive testing and chromosomal microarray was performed: Rotterdam region (with a risk >1:200 and NT between 3.0 and 3.4 mm) tested in the period July 2012 to June 2019 and Central Denmark region (with a risk >1:300 and NT between 3.0 and 3.4 mm) tested between September 2015 and December 2018.

Results

A total of 522 fetuses were referred for invasive testing and chromosomal microarray. Meta‐analysis indicated that in 1:7.4 (13.5% [95% CI 8.2%‐21.5%]) fetuses a chromosomal aberration was diagnosed. Of these aberrant cases, 47/68 (69%) involved trisomy 21, 18, and 13 and would potentially be detected by all NIPT approaches. The residual risk for missing a (sub)microscopic chromosome aberration depends on the NIPT approach and is highest if NIPT was performed only for common trisomies–1:21 (4.8% [95% CI 3.2%‐7.3%]). However, it may be substantially lowered if a genome‐wide 10‐Mb resolution NIPT test was offered (~1:464).

Conclusions

Based on these data, we suggest that the NT cut‐off for invasive testing could be 3.0 mm (instead of 3.5 mm) because of the high risk of 1:7.4 for a chromosomal aberration. If women were offered NIPT first, there would be a significant diagnostic delay because all abnormal NIPT results need to be confirmed by diagnostic testing. If the woman had already received a normal NIPT result, the residual risk of 1:21 to 1:464 for chromosome aberrations other than common trisomies, dependent on the NIPT approach, should be raised. If a pregnant woman declines invasive testing, but still wants a test with a broader coverage of clinically significant conditions then the genome‐wide >10‐Mb resolution NIPT test, which detects most aberrations, could be proposed.