Chromosomal Microarray Analysis for the Prenatal Diagnosis in Fetuses with Nasal Bone Hypoplasia: A Retrospective Cohort Study

Clinical Experience of Prenatal Chromosomal Microarray Analysis in 6159 Ultrasonically Abnormal Fetuses

A single-center retrospective study of G-band karyotyping and chromosomal microarray analysis (CMA) for the invasive prenatal diagnosis of 6159 fetuses with ultrasound abnormalities was conducted. This study aimed to investigate the incidence rates of chromosomal abnormalities and pregnancy outcomes and postpartum clinical manifestations by long-term follow-up and to explore the correlation between different types of prenatal ultrasound abnormalities and pathogenic chromosomal abnormalities. The overall incidence of pathogenic chromosomal aberrations in fetuses with ultrasound abnormalities was 7.58% (467/6159), which comprised 41.7% (195/467) with chromosome number abnormalities, 57.6% (269/467) with pathogenic copy-number variations (pCNVs), and 0.64% (3/467) with uniparental disomy (UPD). In addition, 1.72% (106/6159) with likely pathogenic copy-number variations (lpCNVs) and 3.04% (187/6159) with variants of unknown significance (VOUS) were detected by CMA. Ultrasound abnormalities were categorized into structural anomalies and soft marker anomalies. The incidence rate of pathogenic and likely pathogenic chromosomal abnormalities was significantly higher among fetuses with structural anomalies than soft markers (11.13% vs 7.59%, p < 0.01). We retrospectively analyzed the prenatal genetic outcomes for a large cohort of fetuses with different types of ultrasound abnormalities. The present study showed that the chromosomal abnormality rate and clinical outcomes of fetuses with different types of ultrasound abnormalities varied greatly. Our data have important implications for prenatal genetic counseling for fetuses with different types of ultrasound abnormalities.

Chromosomal Microarray Analysis in Fetuses With Ultrasonographic Soft Markers: A Meta-Analysis of the Current Evidence

BACKGROUND

Ultrasonographic soft markers are normal variants, rather than fetal abnormalities, and guidelines recommend a detailed survey of fetal anatomy to determine the necessity of antenatal karyotyping. Anecdotal reports have described cases with ultrasonographic soft markers in which chromosomal microarray analysis (CMA) revealed pathogenic copy number variants (CNVs) despite normal results on conventional karyotyping, but CMA for ultrasonographic soft markers remains a matter of debate. In this systematic review, we evaluated the clinical significance of CMA for pregnancies with isolated ultrasonographic soft markers and a normal fetal karyotype.

METHODS

An electronic search was conducted by an experienced librarian through the MEDLINE, Embase, and Cochrane CENTRAL databases. We reviewed 3,338 articles (3,325 identified by database searching and 13 by a hand search) about isolated ultrasonographic soft markers, and seven ultrasonographic markers (choroid plexus cysts, echogenic bowel, echogenic intracardiac focus, hypoplastic nasal bone, short femur [SF], single umbilical artery, and urinary tract dilatation) were included for this study.

RESULTS

Seven eligible articles were included in the final review. Pathogenic or likely pathogenic CNVs were found in fetuses with isolated ultrasonographic soft markers and a normal karyotype. The overall prevalence of pathogenic or likely pathogenic CNVs was 2.0% (41 of 2,048). The diagnostic yield of CMA was highest in fetuses with isolated SF (9 of 225, 3.9%).

CONCLUSION

CMA could aid in risk assessment and pregnancy counseling in pregnancies where the fetus has isolated ultrasonographic soft markers along with a normal karyotype.

Residual risk of clinically significant copy number variations in fetuses with nasal bone absence or hypoplasia after excluding non-invasive prenatal screening-detectable findings

BACKGROUND

It remains controversial whether prenatal screening or diagnostic testing should be offered to fetuses with nasal bone (NB) absence or hypoplasia, and there are no studies comparing the yield of chromosomal microarray analysis (CMA) to non-invasive prenatal screening (NIPS). The aim of this study was to evaluate the residual risk of clinically significant copy number variations (CNVs) in fetuses with NB absence or hypoplasia after excluding theoretically NIPS-detectable abnormalities, and to assess their clinical outcomes.

METHODS

This prospective study encompassed 400 fetuses with NB absence or hypoplasia undergoing CMA testing between 2015 and 2022. Clinically significant CMA findings were categorized into three subgroups, including three-NIPS-detectable (trisomies 21, 18 and 13), five-NIPS-detectable (trisomies 21, 18 and 13 and sex chromosome aneuploidies) and genome-wide NIPS-detectable (variants over 7 Mb). We calculated the theoretical residual risk and compared it with the results of a control cohort of low-risk pregnancies. We further evaluated their clinical outcomes.

RESULTS

The overall diagnostic yield in our cohort was 7.8% (31/400). The detection rate of clinically significant CMA findings in fetuses with non-isolated NB absence or hypoplasia was significantly higher than that in fetuses with isolated NB absence or hypoplasia (20.0% vs. 6.6%, P =.005). The theoretical residual risks in all NIPS models were significantly higher when compared with the control cohort. The normal infant rate in fetuses with normal CMA results was 97.9% (323/330), and a significant higher incidence was observed in fetuses with isolated NB absence or hypoplasia compared with non-isolated NB absence or hypoplasia (98.4% vs. 91.7%, P =.028).

CONCLUSIONS

The residual risk of clinically significant CNVs in fetuses with NB absence or hypoplasia following the exclusion of theoretically NIPS-detectable findings was higher than that in low-risk pregnancies. This risk should be considered in genetic counseling to make a more comprehensive and precise choice regarding prenatal genetic testing.

Assessing the value of second-trimester nasal bone hypoplasia in predicting chromosomal abnormalities: a retrospective chromosomal microarray analysis of 351 fetuses

PURPOSE

To evaluate the value of fetal nasal bone hypoplasia and other prenatal risk factors in predicting chromosomal abnormalities.

METHODS

In this retrospective cohort study, we collected data on singleton pregnancies diagnosed with fetal nasal bone hypoplasia during second-trimester ultrasound. Fetal karyotyping and chromosomal microarray analysis (CMA) were performed, and pregnancy outcomes were assessed. The association between fetal nasal bone hypoplasia and chromosomal abnormalities was evaluated according to whether other prenatal risk factors were observed.

RESULTS

Our final analysis included 351 pregnancies, of which 62 (17.7%) fetuses had chromosomal abnormalities, including 36 cases of trisomy-21, six cases of trisomy-18, one case each of trisomy-13, and 47, XYY syndrome, and 18 cases of copy number variations (CNVs). Among the 243 cases of isolated nasal bone hypoplasia, 28 (11.5%) cases of chromosomal aberrations were identified. The incidence was significantly higher if other soft markers or structural abnormalities were simultaneously detected. Pregnancy was terminated in 43 aneuploid fetuses and nine fetuses detected with CNVs. The parents of the fetuses diagnosed with 47, XYY syndrome and the other nine CNVs chose to continue the pregnancy, and no abnormalities were detected in the newborns. Furthermore, we found that other prenatal risk factors should be considered in evaluating the likelihood of chromosomal abnormalities in fetuses with nasal bone hypoplasia.

CONCLUSIONS

Nasal bone hypoplasia is a highly specific soft marker that is associated with multiple chromosomal abnormalities. The risk of chromosomal abnormalities increases when combined with structural abnormalities or increased nuchal translucency (NT). Chromosomal microarray analysis is a powerful prenatal test for chromosomal abnormalities, which may be warranted in fetuses with nasal bone hypoplasia.

Prenatal diagnosis and outcomes in 320 fetuses with nasal bone anomalies

Object: To investigate the chromosome abnormalities associated with absent or hypoplastic fetal nasal bone. Methods: Patients with fetal nasal bone anomalies (NBA) referred to our center for prenatal diagnosis between 2017 and 2021 were retrospectively evaluated. All these patients underwent chromosomal microarray and/or karyotyping and received genetic counseling before and after testing. Results: Among 320 fetuses with NBA, chromosomal abnormalities were diagnosed in 89 (27.8%) cases, including 53 cases of trisomy 21, which was the most common type of chromosomal aneuploidy, accounting for 59.6% of all detected abnormalities. In addition to aneuploidies, 29 cases of copy number variants (CNVs) were detected. In cases of isolated NBA with low-risk screening results and without other risk factors, the incidence of fetal chromosomal aneuploidies and pathogenic CNVs is 5.3% (7 in 132 cases). Conclusion: This study suggests that parents of fetuses should be informed about the possibility of fetal aneuploidy and pathogenic CNVs and that discussion with the parents is also recommended, providing data support and reference for clinical counseling.

Prenatal chromosomal microarray analysis in foetuses with isolated absent or hypoplastic nasal bone

OBJECTIVES

To evaluate the efficiency of chromosomal microarray analysis (CMA) in the prenatal diagnosis of foetuses with isolated absent or hypoplastic nasal bone (NB) in the first and second trimester.

METHODS

From January 2015 to April 2021, foetuses with isolated absent or hypoplastic NB who received invasive prenatal diagnosis were enrolled. The results of CMA were analysed.

RESULTS

There were 221 foetuses, including 166 cases with isolated absent NB and 55 cases with isolated hypoplastic NB. Twenty-four foetuses (10.9%, 24/221) had an ultrasonic diagnosis in the first trimester and 197 (89.1%, 197/221) had a ultrasonic diagnosis in the second trimester. The overall diagnostic yield of CMA was 9.0% (20/221). Aneuploidies were detected in 13 (5.9%, 13/221) foetuses, including 10 Down syndrome, 2 Klinefelter's syndrome and 1 trisomy 18. Pathogenic copy number variations (CNVs) were detected in seven foetuses (3.2%, 7/221). In addition, variants of unknown significance (VOUS) were detected in four foetuses. The foetuses with isolated absent NB had a higher detection rate of chromosome abnormality than the isolated hypoplastic NB, but the difference was not significant in the statistical analysis (10.2% vs. 5.5%, χ² =0.642, p = .423). No significant difference was observed in the detection rate between the first trimester and the second trimester (16.6% vs. 8.1%, χ² = 1.002, p = .317, Chi-square test).

CONCLUSION

CMA can increase the diagnostic yield of chromosome abnormality, especially pathogenic CNVs for foetuses with isolated absent or hypoplastic NB. CMA should be recommended when isolated absent or hypoplastic NB is suspected antenatally.7.

Fetal Nasal Bone Hypoplasia in the Second Trimester as a Marker of Multiple Genetic Syndromes

Nasal bone hypoplasia is associated with a trisomy of chromosome 21, 18 or 13. Nasal bone hypoplasia can also be seen in other, rarer genetic syndromes. The aim of the study was to evaluate the potential of nasal bone hypoplasia, in the second trimester of pregnancy, as a marker of fetal facial dysmorphism, associated with pathogenic copy number variation (CNV). This retrospective analysis of the invasive tests results in fetuses with nasal bone hypoplasia, after excluding those with trisomy 21, 18 and 13. In total, 60 cases with nasal bone hypoplasia were analyzed. Chromosomal aberrations were found in 7.1% of cases of isolated nasal bone hypoplasia, and in 57% of cases of nasal bone hypoplasia with additional malformations. Additionally, in four of nine cases with non-isolated nasal bone hypoplasia but normal CMA results, a monogenic disease was diagnosed. Non-isolated hypoplastic nasal bone appears to be an effective objective marker of fetal facial dysmorphism, associated with pathogenic CNVs or monogenic diseases. In isolated cases, chromosomal microarray testing can be of additional value if invasive testing is performed, e.g., for aneuploidy testing after appropriate counseling.

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.