Prenatal genetic diagnosis using microarray analysis in fetuses with congenital heart defects

Should Prenatal Chromosomal Microarray Analysis Be Offered for Pulmonary Atresia? A Single-Center Retrospective Study in China

(1) Objective: To evaluate the application of chromosomal microarray analysis (CMA) in fetuses with pulmonary atresia (PA) and to explore the risk factors for predicting chromosomal imbalances and adverse perinatal outcomes. (2) Methods: This study investigated 428 cases of PA singleton pregnancies that were tested using CMA and quantitative fluorescent polymerase chain reaction (QF-PCR) as first-line genetic testing. The PA cases were divided into two groups: an isolated group and a non-isolated group. (3) Results: CMA revealed clinically relevant copy number variations (CNVs) in 9/139 (6.47%) PA fetuses, i.e., pathogenic copy number variations (pCNVs) in 8/139 (5.76%) fetuses and likely pathogenic CNVs in 1/139 (0.72%) fetuses. Stratified analysis showed that the incidence of clinically significant variants was higher in non-isolated PA fetuses than in isolated PA fetuses (12.50%, 6/48 vs. 3.30%, 3/91, p = 0.036). Regression analysis showed that a combination of other structural abnormalities at diagnosis of PA represented the principal risk factor for chromosomal imbalances (OR = 2.672). A combination of other structural abnormalities and a high maternal age increased the risk of adverse pregnancy outcomes in PA cases, including intrauterine fetal death (IUFD), termination of pregnancy (TOP), and preterm delivery. (4) Conclusions: The value of CMA for locating imbalanced genetic variations in fetuses with PA was highlighted by this study, particularly when combined with additional structural abnormalities.

Chromosomal Microarray Analysis in Fetuses Detected with Isolated Cardiovascular Malformation: A Multicenter Study, Systematic Review of the Literature and Meta-Analysis

Cardiovascular malformations (CVM) represent the most common structural anomalies, occurring in 0.7% of live births. The CVM prenatal suspicion should prompt an accurate investigation with fetal echocardiography and the assessment through genetic counseling and testing. In particular, chromosomal microarray analysis (CMA) allows the identification of copy number variations. We performed a systematic review and meta-analysis of the literature, studying the incremental diagnostic yield of CMA in fetal isolated CVM, scoring yields for each category of heart disease, with the aim of guiding genetic counseling and prenatal management. At the same time, we report 59 fetuses with isolated CVM with normal karyotype who underwent CMA. The incremental CMA diagnostic yield in fetuses with isolated CVM was 5.79% (CI 5.54–6.04), with conotruncal malformations showing the higher detection rate (15.93%). The yields for ventricular septal defects and aberrant right subclavian artery were the lowest (2.64% and 0.66%). Other CVM ranged from 4.42% to 6.67%. In the retrospective cohort, the diagnostic yield was consistent with literature data, with an overall CMA diagnostic yield of 3.38%. CMA in the prenatal setting was confirmed as a valuable tool for investigating the causes of fetal cardiovascular malformations.

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.

Genetic anomalies in fetuses with tetralogy of Fallot by using high-definition chromosomal microarray analysis

Background

The etiology of TOF is complex and the genesis of TOF has been associated with environmental factors and genetic disorders, including chromosomal anomalies, aneuploidies, 22q11.2 deletion and single-gene disease. Previous literatures have shown that a chromosome alteration in about 30% patients with TOF and recently published articles reported that 22q11.2 deletion syndrome accounts for 16% cases with TOF diagnosed postnatally. CMA now is considered as gold standard for detecting genetic anomalies in fetuses with congenital malformations. CMA could detect a 6.6–25% incremental yield of CNVs in CHDs. The aim of this study was to assess the genetic anomalies in fetal tetralogy of Fallot (TOF) by using high-definition CMA.

Methods

This retrospective study reviewed all the fetuses diagnosed with TOF between 2013 and 2018. Prenatal ultrasongraphic findings, including cardiac angle, and the findings of CMA using Affymetrix CytoScan HD array were collected.

Results

Ninety-six fetuses with TOF and known genetic results were enrolled. Right aortic arch was the most common associated anomalies (22.9%). One fetus with trisomy 18, one with 46, XX, t (7;10)(q36;q22), one with 47, XYY and five with trisomy 21 were identified. Clinically significant CNVs occurred in 6.8% and uncertain significant CNVs in 3.4% fetal TOF with normal karyotype. A total of four cases with 22q11.2 microdeletion and two fetuses with Yq11.223q11.23 microduplication have been identified. Genetic anomalies, including chromosomal aberrations and pathogenic CNVs, were significantly higher in the TOF with extracardiac anomaly group than in the TOF without extracardiac anomaly group (P = 0.005). Abnormal cardiac angle was noticed in 24.0% fetal TOF. Genetic anomalies were more common in the TOF with abnormal cardiac angle than with normal cardiac angle (P = 0.001). On the other hand, abnormal cardiac angle was noticed in 64.3% fetal TOF with genetic anomalies while abnormal cardiac angle occurred in 17.1% fetal TOF with normal genetic results (P = 0.001).

Conclusions

Genetic testing should be offered, specially using microarray analysis, for the fetal TOF with abnormal cardiac angle or extracardiac defects.

Clinical value of chromosomal microarray analysis in prenatally diagnosed dextro-transposition of the great arteries

Objectives: To evaluate the usefulness of chromosomal microarray analysis (CMA) in fetuses with dextro-transposition of the great arteries (d-TGA).Methods: Thirty-two fetuses with d-TGA were examined for submicroscopic copy number variations (CNVs) using CMA.Results: Among the 32 d-TGA fetuses, 23 had isolated lesions (71.9%) and nine had other cardiac or extracardiac anomalies (28.1%). CNVs were detected in 16/32 (50%) of the fetuses, including benign CNVs detected in nine fetuses (28.1%), pathogenic CNVs detected in three fetuses (9.4%), and variants of unknown significance (VOUS) detected in four fetuses (12.5%). There was no significant difference in the detection rates of pathogenic CNVs between the isolated and nonisolated groups. All four VOUS were found in the nonisolated group.Conclusion: CMA might be an effective tool for identifying submicroscopic chromosomal aberrations in fetuses with d-TGA.

Microarray analysis: First-trimester maternal serum free β-hCG and the risk of significant copy number variants

OBJECTIVE

To determine whether abnormal levels of first-trimester maternal serum free β-hCG and PAPP-A are associated with significant copy number variants (CNVs) on chromosomal microarray analysis (CMA).

METHODS

Retrospective cohort of singleton prenatal CMA studies (n = 2880). Cases with an abnormal karyotype, benign familial or de novo variants, and absence of heterozygosity were excluded. The prevalence of abnormal serum analytes was compared between patients with significant CNVs (n = 56) and those with normal CMA (n = 884). Odds ratios (ORs) and 95% confidence intervals (CI) were calculated using Fisher's exact test. Mantel-Haenszel method was utilized to adjust ORs for prenatal diagnostic procedure type and indications for testing. Statistical significance was determined as P value < 0.05.

RESULTS

Abnormally low serum free β-hCG (≤0.45 MoM) was associated with an increased risk of significant CNVs (OR 3.53, 95% CI, 1.25-8.66, P < 0.01). This association remained significant after adjusting for abnormal nuchal translucency and advanced maternal age (AMA) (adjusted OR 3.04, 95% CI, 1.05-7.48, P < 0.05) or procedure type and AMA (adjusted OR 3.21, 95% CI 1.13-8.16, P < 0.05). The associations of abnormally high serum free β-hCG, low PAPP-A, and high PAPP-A with significant CNVs were not statistically significant.

CONCLUSION

Low first-trimester serum β-hCG is associated with an increased risk of significant CNVs on CMA.

Detection of copy number variants using chromosomal microarray analysis for the prenatal diagnosis of congenital heart defects with normal karyotype

BACKGROUND

With the increasing availability of chromosomal microarray analysis (CMA) for congenital heart defect (CHD), genetic testing now faces new challenges due to results with uncertain clinical impact. Studies are needed to better define the penetrance of genetic variants. The aim of the study was to examine the association between CMA and CHDs in fetuses with normal karyotype.

METHODS

This was a retrospective study of 190 fetuses with normal karyotype that underwent CMA after a diagnosis of CHD by fetal ultrasound. Invasive prenatal diagnosis was performed between January 2015 and December 2016 at the first affiliated hospital of Air Force Medical University.

RESULTS

Chromosomal microarray analysis detected pathogenic copy number variants (pCNVs) in 13/190 (6.84%) fetuses, likely pCNVs in 5/190 (2.63%), and variants of unknown significance (VOUS) in 14/190 (7.37%). Among those with pCNVs, none (0%) yielded a normal live birth. Among those with likely pCNVs, 2/5 (40.0%) yielded a live birth. Among the fetuses with VOUS, 10/14 (71.5%) yielded a live birth.

CONCLUSION

These results highlight the usefulness of CMA for prenatal genetic diagnosis of fetuses with CHDs and normal karyotype. In fetuses with CHD, the application of CMA could increase the detection rate of pCNVs causing CHDs. In this study, some VOUS were likely pathogenic, but additional studies are necessary to confirm these findings.

Fetal right aortic arch: associated anomalies, genetic anomalies with chromosomal microarray analysis, and postnatal outcome

OBJECTIVES

The aim of the study was to assess the associated prenatal findings, genetic anomalies with chromosomal microarray analysis (CMA) and postnatal outcome of fetal right aortic arch (RAA).

METHODS

This retrospective study reviewed 92 fetuses diagnosed with RAA and the findings of CMA using Affymetrix CytoScan HD array in our institution between 2013 and 2016.

RESULTS

Postnatal data were not available for six cases, and genetic data were not available for 26 cases. Tetralogy of the Fallot was the most frequently associated anomaly. Among the 60 fetuses with known karyotype, one was 46, X, Yqh+, der(13)t(8;13)(q22.3;q33.2), one was 47, XYY and the remaining were normal. Our study showed that CMA could detect uncertain significant copy number variants in 5.2% of fetal RAA and pathogenic copy number variants in 5.2%, all of which were microdeletion in chromosome 22q11.21. The genetic anomalies, gestational age at delivery and postnatal death were not significantly different between RAA-no intracardiac anomalies and RAA-intracardiac anomalies group. One infant with aberrant left subclavian artery needed to perform a surgery for respiratory symptom.

CONCLUSIONS

A right aortic arch is associated with 22q11.2 deletion syndrome in approximately 5% of cases, and, therefore, prenatal testing, preferably using CMA, should be offered. © 2017 John Wiley & Sons, Ltd.

Neurodevelopmental Disorders Associated with Abnormal Gene Dosage: Smith-Magenis and Potocki-Lupski Syndromes

Smith-Magenis syndrome (SMS) and Potocki-Lupski syndrome (PTLS) are reciprocal contiguous gene syndromes within the well-characterized 17p11.2 region. Approximately 3.6 Mb microduplication of 17p11.2, known as PTLS, represents the mechanistically predicted homologous recombination reciprocal of the SMS microdeletion, both resulting in multiple congenital anomalies. Mouse model studies have revealed that the retinoic acid-inducible 1 gene (RAI1) within the SMS and PTLS critical genomic interval is the dosage-sensitive gene responsible for the major phenotypic features in these disorders. Even though PTLS and SMS share the same genomic region, clinical manifestations and behavioral issues are distinct and in fact some mirror traits may be on opposite ends of a given phenotypic spectrum. We describe the neurobehavioral phenotypes of SMS and PTLS patients during different life phases as well as clinical guidelines for diagnosis and a multidisciplinary approach once diagnosis is confirmed by array comparative genomic hybridization or RAI1 gene sequencing. The main goal is to increase awareness of these rare disorders because an earlier diagnosis will lead to more timely developmental intervention and medical management which will improve clinical outcome.

Prenatal Diagnosis of DNA Copy Number Variations by Genomic Single-Nucleotide Polymorphism Array in Fetuses with Congenital Heart Defects

Objectives: To evaluate the usefulness of single-nucleotide polymorphism (SNP) array for prenatal genetic diagnosis of congenital heart defect (CHD), we used this approach to detect clinically significant copy number variants (CNVs) in fetuses with CHDs. Methods: A HumanCytoSNP-12 array was used to detect genomic samples obtained from 39 fetuses that exhibited cardiovascular abnormalities on ultrasound and had a normal karyotype. The relationship between CNVs and CHDs was identified by using genotype-phenotype comparisons and searching of chromosomal databases. All clinically significant CNVs were confirmed by real-time PCR. Results: CNVs were detected in 38/39 (97.4%) fetuses: variants of unknown significance were detected in 2/39 (5.1%), and clinically significant CNVs were identified in 7/39 (17.9%). In 3 of the 7 fetuses with clinically significant CNVs, 3 rare and previously undescribed CNVs were detected, and these CNVs encompassed the CHD candidate genes FLNA (Xq28 dup), BCOR (Xp11.4 dup), and RBL2 (16q12.2 del). Conclusion: Compared with conventional cytogenetic genomics, SNP array analysis provides significantly improved detection of submicroscopic genomic aberrations in pregnancies with CHDs. Based on these results, we propose that genomic SNP array is an effective method which could be used in the prenatal diagnostic test to assist genetic counseling for pregnancies with CHDs.

Array comparative genomic hybridization and fetal congenital heart defects: a systematic review and meta-analysis

OBJECTIVE

Array comparative genomic hybridization (aCGH) is a molecular cytogenetic technique that is able to detect the presence of copy number variants (CNVs) within the genome. The detection rate of imbalances by aCGH compared to standard karyotyping and 22q11 microdeletion analysis by fluorescence in-situ hybridization (FISH), in the setting of prenatally-diagnosed cardiac malformations, has been reported in several studies. The objective of our study was to perform a systematic literature review and meta-analysis to document the additional diagnostic gain of using aCGH in cases of congenital heart disease (CHD) diagnosed by prenatal ultrasound examination, with the aim of assisting clinicians to determine whether aCGH analysis is warranted when an ultrasonographic diagnosis of CHD is made, and to guide counseling in this setting.

METHODS

Articles in PubMed, EMBASE and Web of Science databases from January 2007 to September 2014 describing CNVs in prenatal cases of CHD were included. Search terms were: 'array comparative genomic hybridization', 'copy number variants' and 'fetal congenital heart defects'. Articles regarding karyotyping or 22q11 deletion only were excluded.

RESULTS

Thirteen publications (including 1131 cases of CHD) met the inclusion criteria for the analysis. Meta-analysis indicated an incremental yield of 7.0% (95% CI, 5.3-8.6%) for the detection of CNVs using aCGH, excluding aneuploidy and 22q11 microdeletion cases. Subgroup results showed a 3.4% (95% CI, 0.3-6.6%) incremental yield in isolated CHD cases, and 9.3% (95% CI,  6.6-12%) when extracardiac malformations were present. Overall, an incremental yield of 12% (95% CI, 7.6-16%) was found when 22q11 deletion cases were included. There was an additional yield of 3.4% (95% CI, 2.1-4.6%) for detecting variants of unknown significance (VOUS).

CONCLUSIONS

In this review we provide an overview of published data and discuss the benefits and limitations of using aCGH. If karyotyping and 22q11 microdeletion analysis by FISH are normal, using aCGH has additional value, detecting pathogenic CNVs in 7.0% of prenatally diagnosed CHD, with a 3.4% additional yield of detecting VOUS.

BAC chromosomal microarray for prenatal detection of chromosome anomalies in fetal ultrasound anomalies: an economic evaluation

INTRODUCTION

To determine the cost-effectiveness of prenatal chromosomal microarray (CMA) when performed for structural anomalies on fetal ultrasound scan over conventional techniques.

METHOD

A decision tree was populated using data from a prospective cohort of women undergoing testing when a fetal ultrasound scan showed a structural abnormality. Nine strategies of testing were modeled including combinations of the tests: QFPCR, G-band karyotyping, CMA and FISH for DiGeorge (22q) microdeletion.

RESULTS

When CMA costs GBP 405 and using a 1-Mb BAC array it would cost GBP 24,600 for every additional case detected by CMA over a combination of QFPCR, followed by G-band karyotype, followed lastly by FISH (for DiGeorge syndrome). If CMA is performed instead of conventional karyotyping alone it costs GBP 33,000 for every additional case detected. However, if the cost of CMA is reduced to GBP 360 than when CMA is performed instead of conventional karyotyping alone it would cost GBP 9,768 for every additional case detected.

DISCUSSION

The use of a prenatal BAC CMA is not currently cost-effective when compared to other testing strategies. However, as CMA costs decrease and resolution (and detection rates) increase it is likely to become the cost-effective option of the future.

Prenatal diagnosis of congenital heart defect by genome-wide high-resolution SNP array

OBJECTIVE

This study aimed to detect genomic imbalances in fetuses with congenital heart defect (CHD) by high-resolution single-nucleotide polymorphism (SNP) array.

METHODS

A total of 99 fetuses with CHDs with or without other ultrasound anomalies (including structural anomalies and soft markers) but normal karyotypes were investigated using Affymetrix CytoScan HD array.

RESULTS

Clinical significant copy number variations (CNVs) were detected in 19 fetuses (19.2%). The proportion for variants of unknown significance was 3% after parental analysis. Five known microdeletion/microduplication syndromes were identified. The detection rate in CHD plus structural anomaly (27.8%) or soft marker (25%) group was higher than but not statistically different from isolated CHD group (15.9%). There was no significant difference between the detection rates in simple and complex CHD groups (20.7% vs. 16.7%). The detection rate in fetuses with CHD and neurologic defect was significantly higher than those with other types of structural anomaly (75% vs. 14.3%, P < 0.05).

CONCLUSIONS

Our results demonstrated the value of high-resolution SNP arrays in prenatal diagnosis of CHD; it should become an integral aspect in clinically molecular diagnosis and genetic counseling. The complexity of the cardiac defect was not related to the frequency of clinical significant CNV, but the presence of neurologic defect was related.

Detection of submicroscopic chromosomal aberrations by array-based comparative genomic hybridization in fetuses with congenital heart disease

OBJECTIVES

To evaluate the usefulness of array-based comparative genomic hybridization (aCGH) for prenatal genetic diagnosis of congenital heart disease (CHD), with and without associated anomalies, and to explore the relationship between submicroscopic chromosomal aberrations and CHD.

METHODS

In this prospective study we investigated 76 consecutive singleton fetuses with abnormal cardiac ultrasound findings, normal karyotype and negative or no fluorescence in-situ hybridization results for 22q11.2 deletion syndrome. All pregnancies underwent aCGH in a comprehensive search for chromosomal aberrations. The relationship between copy number variations (CNVs) and CHD was determined by comparing clinical findings to chromosomal databases.

RESULTS

CNVs that were benign or had no clinical significance were detected in 18/76 (23.7%) cases. CNVs of unknown clinical significance (i.e. VOUS) were detected in 4/76 (5.3%) cases. Pathogenic CNVs were detected in 5/76 (6.6%) cases. Fetuses with CHD and additional structural abnormalities demonstrated no difference in number of pathogenic CNVs when compared with fetuses with isolated CHD (7.4% (n = 2/27) vs 6.1% (n = 3/49), P > 0.05).

CONCLUSION

In this study cohort, aCGH analysis significantly improved the detection of submicroscopic chromosomal aberrations in pregnancies with CHD, as compared with conventional cytogenetics. Our results suggest that aCGH can provide additional genetic information in fetuses with abnormal heart findings.

Additional value of prenatal genomic array testing in fetuses with isolated structural ultrasound abnormalities and a normal karyotype: a systematic review of the literature

OBJECTIVE

To establish the prevalence of submicroscopic genetic copy number variants (CNVs) in fetuses with a structural ultrasound anomaly (restricted to one anatomical system) and a normal karyotype. The aim was to determine the diagnostic and prognostic value of genomic array testing in these pregnancies.

METHODS

Embase and PubMed databases were systematically searched for all relevant articles on prevalence of pathogenic submicroscopic CNVs in fetuses with ultrasound anomalies. Reported cases were sorted into groups according to anatomical site of the detected ultrasound anomaly. The prevalence of causative submicroscopic CNVs was calculated for each group.

RESULTS

Combined data of the reviewed studies (n = 18) indicated that fetuses with an ultrasound anomaly restricted to one anatomical system (n = 2220) had a 3.1-7.9% chance of carrying a causative submicroscopic CNV, depending on the anatomical system affected. This chance increased to 9.1% for fetuses with multiple ultrasound anomalies (n = 1139).

CONCLUSION

This review indicates that 3.1-7.9% of fetuses with a structural ultrasound anomaly restricted to one anatomical system and a normal karyotype will show a submicroscopic CNV, which explains its phenotype and provides information for fetal prognosis. Therefore, we conclude that microarray has considerable diagnostic and prognostic value in these pregnancies.

Microarray-based prenatal diagnosis for the identification of fetal chromosome abnormalities

The goal of prenatal cytogenetic testing is to provide reassurance to the couple seeking testing for their pregnancy, identify chromosome abnormalities in the fetus, if present, and provide treatments and medical management for affected babies. Cytogenetic analysis of banded chromosomes has been the standard for identifying chromosome abnormalities in the fetus for over 40 years. With chromosome analysis, whole chromosome aneuploidies and large structural rearrangements can be identified. The sequencing of the human genome has provided the resources to develop molecular tools that allow higher resolution observations of human chromosomes. The future holds the promise of sequencing that may identify chromosomal imbalances and deleterious single nucleotide variants. This review will focus on the use of genomic microarrays for the testing and identification of chromosome anomalies in prenatal diagnosis and will discuss the future directions of fetal testing.

Use of prenatal chromosomal microarray: prospective cohort study and systematic review and meta-analysis

OBJECTIVES

Chromosomal microarray analysis (CMA) is utilized in prenatal diagnosis to detect chromosomal abnormalities not visible by conventional karyotyping. A prospective cohort of women undergoing fetal CMA and karyotyping following abnormal prenatal ultrasound findings is presented in the context of a systematic review and meta-analysis of the literature describing detection rates by CMA and karyotyping.

METHODS

We performed a prospective cohort study of 243 women undergoing CMA alongside karyotyping when a structural abnormality was detected on prenatal ultrasound. A systematic review of the literature was also performed. MEDLINE (1970-Dec 2012), EMBASE (1980-Dec 2012) and CINAHL (1982-June 2012) databases were searched electronically. Selected studies included > 10 cases and prenatal CMA in addition to karyotyping. The search yielded 560 citations. Full papers were retrieved for 86, and 25 primary studies were included in the systematic review.

RESULTS

Our cohort study found an excess detection rate of abnormalities by CMA of 4.1% over conventional karyotyping when the clinical indication for testing was an abnormal fetal ultrasound finding; this was lower than the detection rate of 10% (95% CI, 8-13%) by meta-analysis. The rate of detection for variants of unknown significance (VOUS) was 2.1% (95% CI, 1.3-3.3%) when the indication for CMA was an abnormal scan finding. The VOUS detection rate was lower (1.4%; 95% CI, 0.5-3.7%) when any indication for prenatal CMA was meta-analyzed.

CONCLUSION

We present evidence for a higher detection rate by CMA than by karyotyping not just in the case of abnormal ultrasound findings but also in cases of other indications for invasive testing. It is likely that CMA will replace karyotyping in high-risk pregnancies.

Prenatal diagnosis of chromosomal abnormalities in fetuses with abnormal cardiac ultrasound findings: evaluation of chromosomal microarray-based analysis

OBJECTIVES

To assess the frequency of karyotype abnormalities and chromosome 22q11.2 deletion syndrome among fetuses with abnormal cardiac ultrasound findings, and to evaluate the clinical value of chromosomal microarray-based analysis (CMA) in the study of such pregnancies.

METHODS

First, we carried out retrospective analysis of karyotype abnormalities and 22q11.2 deletion syndrome cases diagnosed between January 2009 and December 2011 in our center among fetuses with abnormal cardiac ultrasound findings (n = 276). Second, CMA was performed in 51 of the fetuses with such findings, normal karyotype and negative or no 22q11.2 deletion syndrome study, and in the only fetus with a heart defect and an apparently balanced de novo chromosomal rearrangement.

RESULTS

Out of the 276 pregnancies with abnormal cardiac ultrasound findings, karyotyping revealed a chromosomal abnormality in 44 (15.9%). Of fetuses with normal karyotype in which 22q11.2 deletion syndrome studies were performed, 6.4% (5/78) had this microdeletion syndrome. Among fetuses with abnormal cardiac findings, normal karyotype and negative or no 22q11.2 deletion syndrome study that underwent CMA, the detection rate of pathogenic copy number variants not detected by conventional cytogenetics was 2.0% (1/51), and no variants of uncertain clinical significance were found. In the fetus with a heart defect and an apparently balanced de novo chromosomal rearrangement, CMA revealed that the rearrangement was not truly balanced.

CONCLUSIONS

In the assessment of genetic abnormalities in pregnancies with abnormal cardiac ultrasound findings, the diagnostic yield may be increased by 2% if CMA is used as a complementary tool to conventional cytogenetics. Our results suggest that CMA could be a good alternative to karyotyping in these pregnancies.

Prenatal microarray analysis as second-tier diagnostic test: single-center prospective study

OBJECTIVE

To evaluate the usefulness of chromosome microarrays as a second-tier test in prenatal genetic testing.

METHODS

We prospectively analyzed 75 high-risk pregnancies undergoing invasive prenatal genetic testing in which the karyotype either was normal or had findings other than a common non-mosaic autosomal aneuploidy.

RESULTS

Chromosomal microarray analysis (CMA) was performed successfully in all cases. Pathological copy-number variations (CNVs) explaining the phenotypes were found in 11 cases (14.7%). Four cases were detected with an unbalanced translocation. In three of these cases, subsequent genetic analysis demonstrated that a parent was an unknown carrier of a balanced translocation. Among the 67 cases with normal karyo-types, submicroscopic rearrangements with pathological significance were detected in five (7.5%) and CNVs of unclear significance were detected in one (1.5%). CMA was able to discriminate correctly between true mosaicism and confined or pseudomosaicism in all six mosaic cases.

CONCLUSION

CMA is a valuable second-tier test in high-risk pregnancies for which identification or further delineation of genetic aberrations is important. Its higher resolution results in a higher detection rate of aberrant cases, with a clear clinical benefit for estimation of risk of recurrence.