Chromosomal microarray as primary diagnostic genomic tool for pregnancies at increased risk within a population-based combined first-trimester screening program

The Diagnostic Yield of Chromosomal Microarray Analysis in Third-Trimester Fetal Abnormalities

OBJECTIVE

 This study aimed to determine the diagnostic yield of chromosomal microarray analysis (CMA) performed in cases of fetal abnormalities detected during the third trimester of pregnancy.

STUDY DESIGN

 A retrospective review of medical records was conducted for women who underwent amniocentesis at or beyond 28 weeks of gestation between January 2017 and February 2023. CMA results of pregnancies with abnormal sonographic findings not detected before 28 weeks were included.

RESULTS

 A total of 482 fetuses met the inclusion criteria. The average maternal age was 31.3 years, and the average gestational age at amniocentesis was 32.3 weeks. The overall diagnostic yield of CMA was 6.2% (30 clinically significant copy number variations [CNVs]). The yield was 16.4% in cases with two or more fetal malformations, while cases with a single anomaly revealed a diagnostic yield of 7.3%. Cases presenting isolated polyhydramnios or isolated fetal growth restriction had a lower yield of 9.3 and 5.4%, respectively. Of the 30 clinically significant cases, 19 (or 63.4%) exhibited recurrent CNVs. The remaining 11 cases (or 36.6%) presented unique CNVs. The theoretical yield of Noninvasive Prenatal Testing (NIPT) in our cohort is 2% for aneuploidy, which implies that it could potentially miss up to 70% of the significant findings that could be identified by CMA. In 80% of the fetuses (or 24 out of 30) with clinically significant CNVs, the structural abnormalities detected on fetal ultrasound examinations corresponded with the CMA results.

CONCLUSION

 The 6.2% detection rate of significant CNVs in late-onset fetal anomalies confirms the value of CMA in third-trimester amniocentesis. The findings underscore the necessity of CMA for detecting CNVs potentially overlooked by NIPT and emphasize the importance of thorough genetic counseling.

KEY POINTS

· CMA yields 6.2% for third-trimester anomalies.. · NIPT may miss 70% of CMA findings.. · Ultrasound matched 80% of CMA results..

Placental mosaicism for autosomal trisomies: comprehensive follow-up of 528 Danish cases (1983-2021)

BACKGROUND

Mosaicism, characterized by the presence of two or more chromosomally distinct cell lines, is detected in 2% to 4% of chorionic villus samples (CVSs). In these cases, the aberration may be confined to the placenta or additionally present in the fetus. Fetal involvement may manifest as fetal malformations, while confined placental mosaicism (CPM) poses risks such as preterm birth and low birth weight. Differentiating between true fetal mosaicism and CPM at the time of the chorionic villus sampling is challenging and requires follow-up by an amniocentesis and ultrasonography.

OBJECTIVE

To estimate the risk of fetal involvement or adverse pregnancy outcomes for specific chromosomes after detecting mosaicism for an autosomal trisomy in a CVS and identify high (red), intermediate (yellow), and low (green) risk chromosomes. Further, to explore possible associations with level of mosaicism and screening parameters.

STUDY DESIGN

A retrospective descriptive study of all singleton pregnancies with mosaicism detected in CVSs from 1983 to 2021 identified in the Danish Cytogenetic Central Registry and the Danish Fetal Medicine Database.

RESULTS

Of 90,973 CVSs, 528 cases had mosaicism involving an autosomal trisomy and where genetic follow-up had been performed. The overall risk of fetal involvement was 13% (69/528) with extensive variations depending on which chromosome was involved (eg, trisomy 7: 0% [0/55] or trisomy 21: 46% [19/41]). Higher levels of mosaicism in the CVS suggested fetal involvement as mean mosaic level was 55% in true fetal mosaics vs 28% in cases confined to the placenta (P=.0002). In cases with CPM (459/528), the risk of delivering small-for-gestational-age neonates was 14% (48/341). The risk of preterm birth (before 37 weeks) was 15% (51/343). The collective risk of adverse outcome was 22% (76/343) in pregnancies that continued and where information on birth weight and gestational age at birth was available. Adverse outcomes varied substantially between chromosomes. Also, multiple-of-the-median (MoM) values of pregnancy-associated plasma protein A was predictive of these issues as it was significantly lower in cases with adverse outcome compared to cases with a normal outcome (small for gestational age: 0.23 MoM vs 0.47 MoM, P<.0001) or preterm birth: 0.25 MoM vs 0.47 MoM, P<.0001). After the introduction of combined first-trimester screening (cFTS) in 2004, the detection of cases with fetal involvement seemed to increase as the risk before 2004 was 9% (16/174) compared to 15% (53/354) after 2004 (risk ratio: 1.7 [95% CI: 1.0; 2.8]). The risk of adverse outcome in CPM pregnancies increased from 16% (22/139) before 2004 to 27% (55/204) after 2004 (risk ratio 1.7 [95% CI: 1.1; 2.7]).

CONCLUSION

Introducing cFTS increased the detection of placental mosaicism with fetal involvement and CPM with adverse outcome. In cases of mosaicism in CVSs, the risk of fetal involvement and adverse outcomes varied considerably between chromosomes. Importantly, adverse outcomes were seen in CPM for many trisomies besides trisomy 16.

Use of cell-free non-invasive prenatal testing in pregnancies affected by placental mosaicism

OBJECTIVE

To evaluate cell-free non-invasive prenatal testing (cfNIPT) in pregnancies affected by mosaicism.

METHOD

We assessed paired cfNIPT and chorionic villus sample (CVS) results from the same pregnancies in a case series of mosaicism detected in Central and North Denmark Regions from April 2014 to September 2018. Indications for the clinically obtained CVS, pregnancy markers and outcome were retrieved from The Danish Fetal Medicine Database.

RESULTS

Mosaicisms in CVS involved common aneuploidy, n = 14; sex chromosomal aneuploidies, n = 14; rare autosomal trisomies (RATs), n = 16 and copy number variants (CNVs) >5Mb, n = 9. Overall, 24/53 (45.3%; CI 95%: 31.8%-59.4%) of cases with mosaicism were detected by cfNIPT; highest for RATs (56%) and lowest for CNVs (22%). CfNIPT more commonly detected high-level than low-level mosaic cases (p = 0.000). CfNIPT detected 7/16 (43.8%; CI 95%: 21%-69%) clinically significant mosaic cases, either true fetal mosaicism or confined placental mosaicisms with adverse pregnancy outcome. There was a trend toward a higher risk for adverse outcome in pregnancies where mosaicism was detected by cfNIPT compared to pregnancies where mosaicism was not detected by cfNIPT (p = 0.31).

CONCLUSION

CfNIPT has a low detection rate of mosaicism, including pregnancies with clinically significant mosaicism. However, abnormal cfNIPT results may be a predictor of adverse pregnancy outcomes.

Has the introduction of increased genetic prenatal testing affected rates of termination of pregnancy due to fetal abnormality?

OBJECTIVE

Genetic high-resolution analyses and improved diagnostic imaging have impacted the ability to detect fetal disorders. It is unknown if this resulted in an alteration in the number of terminations of pregnancy due to fetal anomalies (TOPFA). The objective was to describe the incidence and indication of TOPFA.

METHODS

A descriptive study based on records from the Regional Abortion Council in the Central Denmark Region from 2008 to 2021 consisting of 1895 TOPFA.

RESULTS

A consistent incidence of TOPFA was observed, accounting for 0.96% of the total births during that period. When examining fetal indications, there was a small increase in the occurrence of genetic aberrations, primarily caused by deletions, duplications, and single nucleotide variations, whereas the number of chromosomal aberrations remained stable. Of 35.5% of the cases with malformations, the central nervous system was the most affected organ system, followed by malformations of the heart 29.6%. Overall, the total number of cases remained stable.

DISCUSSION AND CONCLUSION

Unexpectedly, despite the development of new diagnostic tools, the incidence of TOPFA from 2008 to 2021 remained stable. However, the number of cases with genetic aberrations increased. This may be attributed to increased genetic testing for fetuses with identified malformations, resulting in more accurate diagnoses.

A decade of change - lessons learned from prenatal diagnostics in Central Denmark region in 2008-2018

INTRODUCTION

In 2011, it was decided to implement chromosomal microarray in prenatal testing in the Central Denmark Region, mainly due to the expected higher diagnostic yield. Chromosomal microarray was introduced gradually for an increasing number of pregnancies and without a transition period where both karyotyping and chromosomal microarray were performed: first malformations (2011), then large nuchal translucency (2013), then high risk at combined first trimester risk screening (2016) and finally for all indications (2018). This retrospective study summarizes 11 years of using chromosomal microarray in invasive prenatal testing and presents the effect on diagnostic yield and turnaround time. Furthermore, the concerns when introducing chromosomal microarray are presented and discussed.

MATERIAL AND METHODS

Registry data from the Danish Fetal Medicine Database, the regional fetal medicine database, the Danish Cytogenetic Central Register and the local laboratory database at Department of Clinical Genetics were all combined, and a cohort of 147 158 singleton pregnancies with at least one ultrasound examination was established RESULTS: Of the 147 158 pregnancies, invasive sampling was performed (chorionic villi or amniocytes) in 8456, corresponding to an overall invasive rate of 5.8%. Between 2016 and 2018, 3.4% (95% confidence interval [CI] 2.8-4.2%; n = 86) of the invasive samples (n = 2533) had a disease causing copy number variant and 5.3% (95% CI 4.4-6.2%; n = 133) had trisomies and other aneuploidies. The turnaround time more than halved from 14 days to an average of 5.5 days for chorionic villus sampling.

CONCLUSIONS

Chromosomal microarray identified 5.3% trisomies and 3.4% copy number variants, thereby increased the diagnostic yield by more than 64% compared with karyotype only and it also more than halved the turnaround time. Some preliminary concerns proved real, eg prenatal counseling complexity, but these have been resolved over time in a clinical path with expert consultations.

Detection of copy number variants associated with late-onset conditions in ~16 200 pregnancies: parameters for disclosure and pregnancy outcome

BACKGROUND

Copy number variants (CNVs) associated with late-onset medical conditions are rare but important secondary findings in chromosomal microarray analysis (CMA) performed during pregnancy. Here, we critically review the cases at two tertiary centres to assess the criteria which guide the disclosure of such findings and develop a disclosure decision tool (DDT) aimed at facilitating disclosure decision. Parental decisions on receiving CNVs associated with risks for late-onset conditions were also recorded.

METHODS

Prenatal CMAs in Hadassah and Shaare Zedek Medical Centers from November 2013 to October 2021 were reviewed for CNVs associated with late-onset conditions. The DDT proposed uses a five-parameter scoring system, which considers the severity, median age of onset, penetrance, understanding of genotype-phenotype correlation and actionability of the finding.

RESULTS

Out of 16 238 prenatal CMAs, 16 (0.1%) harboured CNVs associated with late-onset conditions, 15 of which were disclosed. Outcome information was available on 13 of the 16 pregnancies, all of which continued to delivery.

CONCLUSIONS

Our suggested DDT will help clinicians to quantitatively weigh the variables associated with CNVs of this type and arrive at a well thought out clinical decision regarding disclosure. Although the prevalence of late-onset conditions as a major finding in the prenatal setup is low, it is expected to rise with the increasing use of non-invasive CMA testing and whole exome and genome sequencing.

Current Perspectives of Prenatal Cell-free DNA Screening in Clinical Management of First-Trimester Septated Cystic Hygroma

First-trimester septated cystic hygroma occurs in approximately 1 in 268 pregnancies and has long been associated with a markedly increased risk of fetal aneuploidy and, among euploid fetuses, an increased risk of structural anomalies primarily affecting the cardiac and skeletal systems. Invasive prenatal diagnosis – chorionic villus sampling and/or amniocentesis – encompasses the time-honored clinical tools for the next step in management following prenatal sonographic diagnosis of first-trimester septated cystic hygroma. Currently, prenatal cell-free DNA (cfDNA) screening for fetal aneuploidy with select microdeletions is gradually replacing the considerably less sensitive, and labor-intensive combined first-trimester screening. These new technologies have opened potential new venues in the clinical management of this ominous late first-trimester sonographic diagnosis. Advances in cfDNA technologies are now permitting detection of chromosomal copy number variants (CNV) larger than 7Mb across genome and select serious single-gene disorders (mainly impacting skeletal and neurological development), affecting quality of life and may benefit from medical and/or surgical management. This commentary will address the available non-invasive prenatal screening technologies, which clearly enhance immediate genetic analysis modalities applicable in the presence of the complex sonographic finding of first-trimester septated cystic hygroma.

Prenatal Diagnosis Using Chromosomal Microarray Analysis in High-Risk Pregnancies

Background: To assess the value of chromosomal microarray analysis (CMA) during the prenatal diagnosis of high-risk pregnancies. Methods: Between January 2016 and November 2021, we included 178 chorionic villi and 859 amniocentesis samples from consecutive cases at a multiple tertiary hospital. Each of these high-risk singleton pregnancies had at least one of the following indications: (1) advanced maternal age (AMA; ≥35 years; 546, 52.7%); (2) fetal structural abnormality on ultrasound (197, 19.0%); (3) high-risk first- or second-trimester Down syndrome screen (189, 18.2%), including increased nuchal translucency (≥3.5 mm; 90, 8.7%); or (4) previous pregnancy, child, or family history (105, 10.1%) affected by chromosomal abnormality or genetic disorder. Both G-banding karyotype analysis and CMA were performed. DNA was extracted directly and examined with oligonucleotide array-based comparative genomic hybridization. Results: Aneuploidies were detected by both G-banding karyotyping and CMA in 42/1037 (4.05%) cases. Among the 979 cases with normal karyotypes, 110 (10.6%) cases had copy number variants (CNVs) in CMA, including 30 (2.9%) cases with reported pathogenic and likely pathogenic CNVs ≥ 400 kb, 37 (3.6%) with nonreported VOUS, benign, or likely benign CNVs ≥ 400 kb, and 43 (4.1%) with nonreported CNVs < 400 kb. Of the 58 (5.6%) cases with aneuploidy rearrangements, 42 (4.1%) were diagnosed by both G-banding karyotyping and CMA; four inversions, six balanced translocations, and six low mosaic rates were not detected with CMA. Conclusions: CMA is an effective first step for the prenatal diagnosis of high-risk pregnancies with fetal structural anomalies found in ultrasonography or upon positive findings.

Antenatal screening for chromosomal abnormalities

Screening for chromosomal disorders, especially for trisomy 21, has undergone a number of changes in the last 50 years. Today, cell-free DNA analysis (cfDNA) is the gold standard in screening for trisomy 21. Despite the advantages that cfDNA offers in screening for common trisomies, it must be recognized that it does not address many other chromosomal disorders and any of the structural fetal anomalies. In the first trimester, the optimal approach is to combine an ultrasound assessment of the fetus, which includes an NT measurement, with cfDNA testing. If fetal structural defects are detected or if the NT thickness is increased, an amniocentesis or a CVS with at least chromosomal microarray should be offered.

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.

Is Cell-free fetal DNA testing a safe option for women in a high-risk population after combined first-trimester testing?

OBJECTIVES

Our study aimed to examine the relevance of cell-free fetal DNA (cfDNA) testing on the screening of chromosomal defects and the issue of pregnancies in patients with a risk over 1:50 after the first-trimester combined test.

METHODS

This is a retrospective monocentric study. We included all consecutive patients with a singleton pregnancy between January 2015 and December 2020 attending our fetal medicine centre because the estimated risk for trisomy 21 after the first-trimester combined screening was over 1:50. The patients could either choose to have invasive testing or cell-free DNA testing. We collected data about the patient, the tests results (cfDNA, karyotype) and the pregnancy outcome (born alive, medical termination, miscarriage or intrauterine fetal death).

RESULTS

We included 98 patients with an estimated risk for trisomy 21 over 1:50. We found a total of 14 major chromosomal abnormalities (14/98; 14.3%), of which: thirteen trisomies 21 and one triploidy 69, XXY. A cfDNA testing was chosen by 34 (34/98; 34.7%) patients. Among the pathological results of invasive testing, 5 (5/64; 7.8%) couldn't be targeted by cfDNA testing. Two of them were placental mosaicism, one a triploidy 69, XXY, and two defects inherited from a parent and considered benign. There was no miscarriage linked to an invasive test in the population study.

CONCLUSION

In our monocentric cohort, a third of the patients choose cfDNA in a case of a risk over 1:50 after combined testing. Even if this cohort is too small to draw definitive conclusions, cfDNA could be safe in a high-risk population after combined testing. None of the chromosomal abnormalities found at the karyotype and non-detectable by cfDNA was a loss of information that impacted pregnancy follow-up. Further study could explore the input of Genome-Wide cfDNA and chromosomal micro-array in this population.

Initial Clinical Experience with NIPT for Rare Autosomal Aneuploidies and Large Copy Number Variations

OBJECTIVE

Amniocentesis, chorionic villi sampling and first trimester combined testing are able to screen for common trisomies 13, 18, and 21 and other atypical chromosomal anomalies (ACA). The most frequent atypical aberrations reported are rare autosomal aneuploidies (RAA) and copy number variations (CNV), which are deletions or duplications of various sizes. We evaluated the clinical outcome of non-invasive prenatal testing (NIPT) results positive for RAA and large CNVs to determine the clinical significance of these abnormal results.

METHODS

Genome-wide NIPT was performed on 3664 eligible patient samples at a single genetics center. For patients with positive NIPT reports, the prescribing physician was asked retrospectively to provide clinical follow-up information using a standardized questionnaire.

RESULTS

RAAs and CNVs (>7 Mb) were detected in 0.5%, and 0.2% of tested cases, respectively. Follow up on pregnancies with an NIPT-positive result for RAA revealed signs of placental insufficiency or intra-uterine death in 50% of the cases and normal outcome at the time of birth in the other 50% of cases. We showed that CNV testing by NIPT allows for the detection of unbalanced translocations and relevant maternal health conditions.

CONCLUSION

NIPT for aneuploidies of all autosomes and large CNVs of at least 7 Mb has a low "non-reportable"-rate (<0.2%) and allows the detection of additional conditions of clinical significance.

Trends in Non-invasive Prenatal Screening and Invasive Testing in Denmark (2000-2019) and Israel (2011-2019)

Introduction: Following the wide distribution of non-invasive prenatal genetic screening (NIPS), numerous studies have reported a decline in total invasive tests in the recent years, up to 50–70% in some countries. However, in Denmark and Israel we have not experienced these declines. The objective of our study was to evaluate the trends in NIPS and chromosomal microarray analysis (CMA) use in Denmark and Israel.

Methods: This retrospective study was performed by data acquisition from the Danish Cytogenetics Central Registry throughout the years 2000–2019, and Israeli Public Health Services, Ministry of Health computerized database (from 2011).

Results: Of the 1,243,956 live births registered in Denmark over the years 2000–2019, a relatively steady level of invasive testing around 6% was noted since 2004, as opposed to 13.0% in Israel based on 1,594,962 live births between 2011 and 2019. The average uptake of NIPS was 1.1 ± 0.5% in Denmark vs. 4.3% in Israel (2013–2019). Relatively steady rates of invasive testing were noted in both countries, compared to a slight decline in NIPS in the recent years.

Discussion: The recent decrease in the rates of invasive testing in the NIPS era was not observed in Denmark or in Israel. These results imply that Danish and Israeli women and/or health providers might favor the high resolution and yield of CMA testing over the non-invasiveness of NIPS. We explore and discuss this phenomenon, based on five central factors.

SIGNIFICANCE OF LOW MATERNAL SERUM Β-HCG LEVELS IN THE ASSESSMENT OF THE RISK OF ATYPICAL CHROMOSOMAL ABNORMALITIES

INTRODUCTION

The introduction of prenatal cell-free DNA as a screening test has surpassed traditional combined first-trimester screening (cFTS) in the detection of common trisomies. However, its current limitation in detecting only common trisomies is affecting the diagnostic yield for other clinically significant chromosomal abnormalities.

METHODS

In efforts to optimize the detection of fetuses with genetic abnormalities, we have analyzed the relationship between the cFTS risk score and biomarkers with atypical chromosomal abnormalities. Furthermore, we have evaluated the impact of prenatal cell-free DNA screening on the detection of chromosomal abnormalities in our population. For these purposes, we performed a retrospective study of 877 singleton pregnancies who underwent chromosomal microarray analysis (CMA) between 2013 to 2020 and for whom first-trimester screening data were available.

RESULTS

The results demonstrated that low levels of free beta human chorionic gonadotropin (β-hCG) (≤ 0.37 MoM) and increased fetal nuchal translucency (NT) (≥ 3.5mm) were statistically associated with the presence of atypical chromosomal abnormalities. In fact, the risk of pathogenic CMA results increased from 6% to 10% when fetal NT was increased and from 6% to 20% when a low serum β-hCG level was detected in the high-risk cFTS group. Moreover, our results showed that altered serum levels of β-hCG can have a substantial impact on the early detection of clinically relevant copy number variants.

DISCUSSION/CONCLUSION

Traditional cFTS can potentially identify a substantial proportion of atypical chromosomal aberrations, and women with increased NT or low maternal serum β-hCG levels are at increased risk of having pathogenic CMA results. Our results may help clinicians and women decide whether invasive testing or prenatal cell-free DNA screening testing are more appropriate for each situation.

Karyotype analysis of amniotic fluid cells and report of chromosomal abnormalities in 15,401 cases of Iranian women

The aim of present study was to assess the karyotypes of amniotic fluid cells and find the frequency of chromosomal abnormalities and their significance in clinical setting. A total of 15,401 pregnant women were assessed from March 2016 to May 2019, and 14,968 amniotic fluid samples were successfully cultured. These fetuses were grouped according to different indications including advanced maternal age, abnormal nuchal translucency (NT) values, positive first/second trimester screening results, high risk NIPT results, very low PAPP-A and free β-hCG multiples of the normal median (MoM) results, abnormal ultrasound findings or previous history of chromosomal abnormalities. Results indicated the presence of normal karyotype in 90.2% (13,497/14,968) of fetuses. Totally, 46.4% (6945/14,968) of fetuses were 46,XX and 43.8% (6552/14,968) had 46,XY chromosome pattern. A total of 1077 abnormal karyotypes were found among 14,968 fetuses, thus the rate of abnormal fetuses was calculated to be 7.2% (1072/14,968). Meanwhile, a total of 394 cases (2.8%) had a normal polymorphism in their karyotype. In other words, abnormal karyotypes were detected in one of 13.9 cases of patients underwent amniocentesis. Down syndrome, Edward’s syndrome, abnormal mosaicisms and Patau’s syndrome were detected in 4.4% (659/14,968), 0.57% (85/14,968), 0.49% (74/14,968) and 0.24% (36/14,968) of cases, respectively. Sex chromosomal abnormalities including Klinefelter syndrome, Turner syndrome and 47,XXX karyotype were detected in 64 cases (0.43%). In this article, the rates of chromosomal abnormalities are compared between different groups of patients based on the advanced maternal age, abnormal NT values, very low PAPP-A and free β-hCG MoMs results, and positive FTS results. The current investigation provides insight into the most appropriate indications for amniocentesis in Iran.

A two-year prospective study assessing the performance of fetal chromosomal microarray analysis and next-generation sequencing in high-risk pregnancies

Background

Introduction of cell‐free fetal DNA (cff‐DNA) testing in maternal blood opened possibilities to improve the performance of combined first‐trimester screening (cFTS) in terms of better detection of trisomies and lowering invasive testing rate. The use of new molecular methods, such as chromosomal microarray analysis (CMA) and next‐generation sequencing (NGS), has shown benefits in prenatal diagnosis of chromosomal and genetic diseases, which are not detectable with cff‐DNA screening, but require an invasive procedure.

Methods

The objective of this study was to evaluate prospectively during two years performance of CMA and NGS in high‐risk pregnancies. Initially, we investigated 14,566 singleton pregnancies with cFTS. A total of 334 high‐risk pregnancies were selected for CMA diagnostic performance evaluation and 28 cases of highly dysmorphic fetuses for NGS analysis. CMA study group was divided into two groups based on the indications for testing; group A patients with high‐risk for trisomies after cFTS, but normal ultrasound and group B patients who met criteria for CMA as a first‐tier diagnostic test.

Results

The diagnostic yield of CMA was overall 3.6% (1.6% in Group A and 6.0% in Group B). In NGS analysis group, we report diagnostic yield of 17.9%.

Conclusion

The use of CMA in high‐risk pregnancies is justified and provides relevant clinical information in 3.6% of the cases. NGS analysis in fetuses with multiple anomalies shows promising results, but more investigations are needed for a better understanding of practical applications of this molecular diagnosis method in prenatal settings.

Clinicians' attitudes towards parental choice in the era of advanced genomic tests in pregnancy

OBJECTIVE

Israel is one of the first countries to incorporate chromosomal microarray analysis into routine prenatal care. We explored attitudes of Israeli healthcare professionals (HCPs) towards the disclosure of challenging findings: variants of uncertain clinical significance (VUS), susceptibility loci (SL) for neurodevelopmental disorders and variants associated with adult-onset (AO) conditions. Particularly, we sought their views on providing parental choice regarding the disclosure of these findings.

METHODS

Twenty-nine in-depth interviews were conducted with genetic counselors (n = 19), medical geneticists (n = 4), medical geneticists that are trained in and practice fetal medicine (n = 3), and fetal medicine experts (n = 3).

RESULTS

Most participants (n = 24) supported parental choice regarding uncertain genetic information. Engaging parents in disclosure decisions allows avoidance from potentially anxiety-provoking information, practicing parental autonomy, and better preparation in cases where uncertain findings are identified. HCPs believed that given appropriate preparation, parents can make informed decisions. Four participants believed that disclosure should be based on professional judgment and one supported full-disclosure. Unlike VUS or SL, all interviewees agreed that in cases of medically actionable AO conditions, the benefit of disclosure outweighs the damage.

CONCLUSION

HCPs attitudes are largely in-line with the Israeli practice of involving parents in disclosure decisions regarding uncertain information. This may mitigate disclosure dilemmas and allow personalized disclosure based on parents' views.

Mosaicism for copy number variations in the placenta is even more difficult to interpret than mosaicism for whole chromosome aneuploidy

OBJECTIVE

To compare mosaicisms in prenatal chorionic villus samples (CVSs) with corresponding postpartum placental samples.

METHOD

We collected placentas from 15 consecutive cases of mosaicism detected in CVSs and obtained five standardized samples on each placenta after delivery. All pre- and postnatal placental samples were uncultured and analyzed by high-resolution chromosomal microarray.

RESULTS

Ten cases of mosaicism for whole chromosome aneuploidy (mWC) and five cases with mosaicism for (sub)chromosomal copy number variations (mCNVs) were included. In 5/10 mWC cases and in 4/5 mCNV cases the prenatally detected aberration was confirmed in the postpartum placenta. Three postpartum placentas revealed various complex aberrations differing from the prenatal results: (1) mosaicisms for different deletions/duplications on 9p and 9q in all samples (prenatal: mosaic 5.3 Mb duplication on 9p24), (2) different regions with deletions/duplications/loss of heterozygosity on 1p in all samples (prenatal: mosaic 2.3 Mb 1p36 duplication), and (3) mosaicism for a duplication on 5q and a deletion on 6p in one out of five samples (prenatal: mosaic trisomy 7).

CONCLUSION

CNVs constitute a complex subgroup in placental mosaicism. Counseling of these couples after chorionic villus sampling should not focus on the specific CNV involved, but on the nature of mosaicism and the option of amniocentesis and ultrasound.

Is it time for prenatal chromosomal-microarray analysis to all women? A review of the diagnostic yield in structurally normal fetuses

PURPOSE OF REVIEW

Chromosomal-microarray analysis (CMA) is the first-tier test in pregnancies with structural malformations. Accumulating data show that pathogenic copy number variants (CNVs) can also be identified in structurally normal fetuses. We set out to summarize the published data on the diagnostic yield of CMA in structurally normal fetuses.

RECENT FINDINGS

Six studies summarize a total of 29,612 prenatal CMAs performed in structurally normal fetuses. The incidence of highly penetrant pathogenic/likely pathogenic CNVs is 0.4-2.5%. Variability was demonstrated in the timing of CMA testing and type of CNVs classified as pathogenic. The incidence of variants of uncertain significance is 0.4-5.4%. The prevalence of susceptibility loci is 0.3-0.7% when specified, and the incidence of CNVs associated with late onset disease is 0.1%.

SUMMARY

With a frequency of abnormal CNVs of 1:40 to 1:250 in structurally normal fetuses, it is recommended that all pregnant women be informed of the possibility to have CMA performed, even in the absence of malformations. Information should also be provided about uncertain and secondary findings.

Trisomy 8 mosaicism in the placenta: A Danish cohort study of 37 cases and a literature review

OBJECTIVE

To evaluate the risk of fetal involvement when trisomy 8 mosaicism (T8M) is detected in chorionic villus samples (CVS).

METHODS

A retrospective descriptive study of registered pregnancies in Denmark with T8M in CVS identified through a database search and a review of published cases of T8M found through a systematic literature search and inclusion of cross references. Pregnancies with T8M in CVS and no additional numerical chromosomal aberrations were included.

RESULTS

A total of 37 Danish cases and 60 published cases were included. T8M detected in a CVS was associated with fetal involvement in 18 out of 97 pregnancies (18.6% [95%CI: 11.4-27.7]). Eight out of 70 (11.4% [95%CI: 5.1-21.3]) interpreted prenatally to be confined placental mosaicism (CPM) were subsequently found to be true fetal mosaicisms (TFM).

CONCLUSION

T8M detected in CVS poses a significant risk of fetal involvement, and examination of amniotic fluid (AF) and/or fetal tissue should be offered. However, a normal result of AF still has a considerable residual risk of fetal involvement. Genetic counselling at an early gestational age is essential, and follow-up ultrasonography should be performed to predict fetal involvement if possible.

Personalized prenatal genomic testing: Couples' experience with choice regarding uncertain and adult-onset findings from chromosomal-microarray-analysis

BACKGROUND

Chromosomal-microarray-analysis (CMA) can identify variants of uncertain clinical significance, susceptibility-loci for neurodevelopmental conditions, and risk for adult-onset conditions. We explored choices made by couples undergoing prenatal CMA, their understanding of these findings, reasons for and against receiving them, and whether they believe parents or professionals should decide which are disclosed.

METHODS

Semi-structured interviews were conducted with women (n = 27) or their partners (n = 15) during the week following prenatal CMA testing and analyzed using grounded theory.

RESULTS

Over half the interviewees (55%) recalled at least two of the three types of CMA results they chose whether to receive. Sixty-four percent found the choice simple, whereas 36% found it difficult. All participants could clearly explain their choices, which were based on the perceived actionability and psychological impact of the information. Sixty percent viewed their choice favorably, whereas ~21% would have preferred clinicians to decide for them. More women than men, and more decisive than indecisive participants supported parental choice.

CONCLUSION

Overall, expectant parents can make informed choices about which uncertain findings about their fetuses they wish to receive, and value the opportunity to tailor results to their values and wishes. Arguments presented provide the basis for a decision-aid tool for expecting parents.

Increased prenatal detection of 22q11.2 deletion and 22q11.2 duplication after introduction of nationwide prenatal screening for trisomy 21, trisomy 13, and trisomy 18

OBJECTIVE

To evaluate time of diagnosis of 22q11.2 deletion and 22q11.2 duplication as well as trisomies 21, 13, and 18 before and after introduction of a prenatal screening program including combined first-trimester screening (cFTS) for the trisomies in Denmark in 2004.

METHOD

Cross-sectional, population-based register study employing The Danish Cytogenetic Central Register. Proportions of cases diagnosed 1998-2004 and 2005-2017 were compared before 14⁺⁰ and 22⁺⁰ weeks and birth (prenatal cases) or up to 1 or 10 years of age (postnatal cases).

RESULTS

In total, 4562 cases were included. From 1998-2004 to 2005-2017, the proportion of 22q11.2 deletion cases identified prenatally increased from 4.3% (95% CI: 0.9-12.0%) to 27.3% (21.2-34.0%), while for 22q11.2 duplication an increase from 0/6 to 26/87 (prenatal cases/all cases) was observed. Similarly, proportions of trisomies 21, 13, and 18 detected before birth increased. A greater proportion of the studied conditions was identified earlier in pregnancy, but not generally earlier in the postnatal course.

CONCLUSION

Proportions of 22q11.2 deletion and 22q11.2 duplication identified prenatally increased after introduction of a prenatal screening program not aimed specifically to identify these conditions,. A greater proportion of all cases were detected earlier in pregnancy, but not earlier postnatally, following introduction of screening.

Implementation of exome sequencing in fetal diagnostics-Data and experiences from a tertiary center in Denmark

INTRODUCTION

Applying whole-exome sequencing (WES) for the diagnosis of diseases in children has shown significant diagnostic strength compared with chromosomal microarray. WES may also have the potential of adding clinically relevant prenatal information in cases where a fetus is found to have structural anomalies. We present results from the first fetal exomes performed in a tertiary center in Denmark.

MATERIAL AND METHODS

Couples/expectant parents were included in Central Denmark Region from July 2016 to March 2019. Inclusion was not systematic, but where one or more fetal malformations or severe fetal hydrops were detected, and a specific diagnosis had not been obtained by chromosomal microarray. WES was performed in ongoing pregnancies (N = 11), after intrauterine demise (N = 5), or after termination of pregnancy based on ultrasound findings (N = 19). In most cases, a trio format was applied comprising fetal and parental DNA.

RESULTS

WES was performed in 35 highly selected fetal cases. Pathogenic variants, or variants likely to explain the phenotype, were detected in 9/35 (26%). Variants of uncertain significance were detected in 7/35 (20%) and there was one secondary finding (3%). Out of the 11 ongoing pregnancies, four reached a genetic diagnosis (36%). Detection rate was highest in cases of multisystem anomalies (7/13, 54%). WES was completed in all three trimesters and both autosomal dominant, autosomal recessive and X-linked inheritance were revealed.

CONCLUSIONS

We present data from 35 cases of exome sequencing applied in a setting of fetal malformations. Importantly, though, we wish to share our personal experiences with implementing WES into a prenatal setting. As a medical society, we must continue to share what we do not understand, what went wrong, what is difficult, and what we do not agree upon. A common understanding and language are warranted. We also advocate that more research is needed concerning the clinical value, as well as costs and patient perspectives, of using WES in pregnancy. We believe that WES will lead to improved prenatal and perinatal care.

Incidence of chromosomal abnormalities in fetuses with first trimester ultrasound anomalies and a low-risk cell-free DNA test for common trisomies

OBJECTIVE

To examine the incidence and type of chromosomal abnormalities in fetuses with first trimester ultrasound anomalies and a low-risk cfDNA test for common trisomies.

METHODS

In 486 singleton pregnancies undergoing invasive testing after combined screening, a detailed first trimester ultrasound assessment was carried out and a maternal blood sample was sent for cfDNA analysis. Ultrasound and cfDNA data were analyzed in relation to fetal karyotype.

RESULTS

Invasive testing demonstrated a chromosomal abnormality in 157 (32.3%) of 486 fetuses. In 348 cases with a low-risk cfDNA test for common trisomies, NT ≥ 3.5 mm and/or a major structural defect were observed in 92 (26.4%) fetuses. A chromosomal abnormality was found in 17 (18.5%; 95%CI 10.55-26.41) of these pregnancies, including 1 (1.1%) case of trisomy 21 and 16 (17.4%) fetuses with abnormalities different from common trisomies. The respective incidence in the 256 cases with a low-risk cfDNA test result and no ultrasound anomalies was 2.3% (95% CI 0.49-4.20; n = 6).

CONCLUSIONS

In fetuses with first trimester ultrasound anomalies and a low-risk cfDNA result for trisomy 21, 18 and 13, diagnostic testing should be offered with the main objective to detect chromosomal abnormalities beyond common trisomies.

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.

Information Women Choose to Receive About Prenatal Chromosomal Microarray Analysis

OBJECTIVE

To examine the choices of women with both high-risk and low-risk pregnancies who are undergoing prenatal chromosomal microarray analysis in a clinical setting regarding three challenging types of findings: variants of uncertain clinical significance, susceptibility loci for neurodevelopmental disorders, and copy number variants associated with risks for adult-onset conditions. We assessed whether women's choices were associated with indications for testing or with one-on-one pretest genetic counseling.

METHODS

In this cross-sectional study, medical records of women who underwent invasive prenatal chromosomal microarray analysis testing (N=1,070) at Hadassah Medical Center between June 2017 and February 2018 were examined for testing indications, choices regarding chromosomal microarray analysis findings, and type of pretest genetic counseling. Multivariable analyses to assess associations with testing indication and prior genetic counseling were carried out using logistic regression models.

RESULTS

In total, 56% of women (n=593) chose to be informed of all three types of findings and 20% (n=218) chose not to be informed of any of the findings beyond high-penetrance childhood-onset pathogenic findings. Variants of uncertain clinical significance as a single choice was the least-selected finding (2.5%, n=27). Low-risk pregnancies (ie, those with normal biochemical screening and fetal ultrasound examinations) were associated with increased interest in receiving genetic information about adult-onset conditions (adjusted odds ratio [aOR] 1.7; 95% CI 1.18-2.33) and susceptibility loci (aOR 1.5; 95% CI 1.08-2.10).

CONCLUSION

Women with both high-risk and low-risk pregnancies were generally more likely to choose to receive additional genetic information, albeit differences in preferences depend on testing indication and type of pretest counseling.

Fine-tuning of routine combined first- trimester screening: The ratio of serum-free- beta-human chorionic gonadotropin (fβ-hCG) to pregnancy-associated plasma protein-A (PAPP-A) could improve performance of Down syndrome screening program, a retrospective cohort study in Iran

OBJECTIVES

To evaluate the performance of the current national screening policy for Down syndrome (DS) in Iran and suggest a more efficient protocol with a wealth of a large series of first-trimester screening (FTS) data obtained from Nilou medical laboratory. To fulfill this aim, detection rate (DR), positive screening rate (PSR), false negative rate (FNR) and odds of being affected given a positive results (OAPR) were calculated at different cutoff risk. In the latest update of DS screening program in Iran, there is no place for intermediate group to be further investigated. Next, we proposed a novel parameter namely the ratio of fβ-hCG multiple of the median (MoM) value to PAPP-A MoM value to delicately categorize FTS results in a way that reduce FNR without imposing unnecessary anxious and extra money on most families.

METHODS

The present investigation was conducted retrospectively on 197,210 pregnancies undergoing FTS for aneuploidies in Nilou medical laboratory, Tehran, Iran, from March 2015 to February 2016.

RESULTS

Intermediate risk group is important as 23 out of 45 FN fell in the range 1:250 to 1:1100. By applying the proposed index, the ratio of fβ-hCG MoM to PAPP-A MoM and subsequent decision about NIPT, 8 out of 23 FN cases in intermediate group could be detected.

CONCLUSION

Compared with the current policy, our novel proposed approach had better performance and could be applied by the Iran National Health Service to improve the screening program guideline.

Cost-effectiveness analysis of chromosomal microarray as a primary test for prenatal diagnosis in Hong Kong

Background

Chromosomal microarray (CMA) has been shown to be cost-effective over karyotyping in invasive prenatal diagnosis for pregnancies with fetal ultrasound anomalies. Yet, information regarding preceding and subsequent tests must be considered as a whole before the true cost-effectiveness can emerge. Currently in Hong Kong, karyotyping is offered free as the standard prenatal test while genome-wide array comparative genome hybridization (aCGH), a form of CMA, is self-financed. A new algorithm was proposed to use aCGH following quantitative fluorescent polymerase chain reaction (QF-PCR) as primary test instead of karyotyping. This study aims to evaluate the cost-effectiveness of the proposed algorithm versus the current algorithm for prenatal diagnosis in Hong Kong.

Methods

Between November 2014 and February 2016, 129 pregnant women who required invasive prenatal diagnosis at two public hospitals in Hong Kong were prospectively recruited. The proposed algorithm was performed for all participants in this demonstration study. For the cost-effectiveness analysis, cost and outcome (diagnostic rate) data were compared with that of a hypothetical scenario representing the current algorithm. Further analysis was performed to incorporate women’s willingness-to-pay for the aCGH test. Impact of government subsidies on the aCGH test was explored as a sensitivity analysis.

Results

The proposed algorithm dominated the current algorithm for prenatal diagnosis. Both algorithms were equally effective but the proposed algorithm was significantly cheaper (p ≤ 0.05). Taking into account women’s willingness-to-pay for an aCGH test, the proposed algorithm was more effective and less costly than the current algorithm. When the government subsidy reaches 100%, the maximum number of diagnoses could be made.

Conclusion

By switching to the proposed algorithm, cost saving can be achieved whilst maximizing the diagnostic rate for invasive prenatal diagnosis. It is recommended to implement aCGH as a primary test following QF-PCR to replace the majority of karyotyping for prenatal diagnosis in Hong Kong.

Social and medical need for whole genome high resolution NIPT

BACKGROUND

Two technological innovations in the last decade significantly influenced the diagnostic yield of prenatal cytogenetic testing: genomic microarray allowing high resolution analysis and noninvasive prenatal testing (NIPT) focusing on aneuploidy. To anticipate future trends in prenatal screening and diagnosis, we evaluated the number of invasive tests in our center and the number of aberrant cases diagnosed in the last decade.

METHODS

We retrospectively analyzed fetal chromosomal aberrations diagnosed in 2009-2018 in 8,608 pregnancies without ultrasound anomalies.

RESULTS

The introduction of NIPT as the first-tier test led to a substantial decrease in the number of invasive tests and a substantially increased diagnostic yield of aneuploidies in the first trimester. However, we have also noted a decreased detection of submicroscopic aberrations, since the number of invasive tests substantially decreased. We have observed that pregnant women were interested in broader scope of prenatal screening and diagnosis than detection of common trisomies.

CONCLUSION

Since the frequency of syndromic disorders caused by microdeletions/microduplications is substantial and current routine NIPT and ultrasound investigations are not able to detect them, we suggest that a noninvasive test with resolution comparable to microarrays should be developed, which will also meet patient's needs.

Prevalence of mosaicism in uncultured chorionic villus samples after chromosomal microarray and clinical outcome in pregnancies affected by confined placental mosaicism

OBJECTIVE

To evaluate the prevalence of mosaicism in chorionic villus sampling (CVS) samples after chromosomal microarray (CMA) and clinical outcome of pregnancies affected by confined placental mosaicism.

METHOD

We retrieved all results from CMA, array-based comparative genomic hybridization, on CVS samples from January 2011 to November 2017 from Central and North Denmark Regions. Mosaic results from uncultured chorionic villi, cytotrophoblasts and mesenchymal cells, after CVS and follow-up on amniocytes, fetal tissue, or postnatal blood were studied and matched with clinical data from The Danish Fetal Medicine Database.

RESULTS

Prevalence of mosaicism was 93 out of 2,288 (4.1%) CVS samples of which 17 (18.3%) concerned submicroscopic copy number variations (CNVs) <10 Mb. Follow-up analyses were performed in 62 cases. True fetal mosaicism (TFM) was confirmed in 18.4% (7/38) when mosaicism involved whole chromosome aneuploidy and in 25.0% (6/24), when involving a CNV (P = .59). Median birth weight z-score was higher in cases of confined placental mosaicism for a CNV (0.21) than cases involving whole chromosomes (-0.74) (P = .02).

CONCLUSION

Prevalence of mosaicism in CVS samples is higher after CMA on uncultured tissue than after conventional karyotyping on cultured tissue. The risk of TFM is equally high in cases of mosaicism for CNVs and whole chromosomes.

Characteristics and mode of inheritance of pathogenic copy number variants in prenatal diagnosis

BACKGROUND

Microdeletions and microduplications can occur in any pregnancy independent of maternal age. The spectrum and features of pathogenic copy number variants including the size, genomic distribution, and mode of inheritance are not well studied. These characteristics have important clinical implications regarding expanding noninvasive prenatal screening for microdeletions and microduplications.

OBJECTIVES

The aim was to investigate the spectrum and characteristics of pathogenic copy number variants in prenatal genetic diagnosis and to provide recommendations for expanding the scope of noninvasive prenatal screening for microdeletions and microduplications.

STUDY DESIGN

This was a retrospective study of 1510 pregnant women who underwent invasive prenatal diagnostic testing by chromosomal microarray analysis. Prenatal samples were retrieved by amniocentesis or chorionic villus sampling and sent to our prenatal genetic diagnosis laboratory for chromosomal microarray analysis. The risk of carrying a fetus with pathogenic copy number variants is stratified by the patients' primary indication for invasive testing. We searched the literature for published prenatal chromosomal microarray data to generate a large cohort of 23,865 fetuses. The characteristics and spectrum of pathogenic copy number variants including the type of aberrations (gains or losses), genomic loci, sizes, and the mode of inheritance were studied.

RESULTS

Overall, 375 of 23,865 fetuses (1.6%) carried pathogenic copy number variants for any indication for invasive testing, and 44 of them (11.7%) involve 2 or more pathogenic copy number variants. A total of 428 pathogenic copy number variants were detected in these fetuses, of which 280 were deletions and 148 were duplications. Three hundred sixty (84.1%) were less than 5 Mb in size and 68 (15.9%) were between 5 and 10 Mb. The incidence of carrying a pathogenic copy number variant in the high-risk group is 1 in 36 and the low-risk group is 1 in 125. Parental inheritance study results were available for 311 pathogenic copy number variants, 71 (22.8%) were maternally inherited, 36 (11.6%) were paternally inherited, and 204 (65.6%) occurred de novo.

CONCLUSION

Collectively, pathogenic copy number variants are common in pregnancies. High-risk pregnancies should be offered invasive testing with chromosomal microarray analysis for the most comprehensive investigation. Detection limits on size, parental inheritance, and genomic distribution should be carefully considered before implementing copy number variant screening in expanded noninvasive prenatal screening.

[Contribution of array CGH in the management of fetal nuchal translucency]

OBJECTIVES

Increased nuchal translucency and cystic hygroma have a neonatal prognosis, when the karyotype is normal, which depends on the findings during the medical follow-up. Array comparative genomic hybridization (aCGH) has been systematically included in this follow-up by prenatal diagnosis teams. There are no guidelines and little information on the advantages of carrying out this test systematically. The aim of our study is to evaluate the contribution of the aCGH in the medical follow-up.

METHODS

Fifty-one patients were included during 18 months and followed till the end of their pregnancy in prenatal diagnosis centers in Brest and Amiens. Inclusion criterion was a nuchal translucency above 3,5mm on the first trimester ultrasound. A fetal DNA ChromoQuant and aCGH analysis on chorionic villi sampling, and an ultrasound at 18 weeks of gestation were performed during the follow-up.

RESULTS

The aCGH was decisive in only 2 cases. The ultrasound at 18 weeks gestation seemed to be more sensible in the detection of an abnormality. When the aCGH relieved an abnormality, the ultrasound permitted already to detect the presence of a deformity. In 10 cases, the aCGH could not be interpreted on the chorionic villi sampling. In 9 cases, an amniocentesis was performed in order to obtain this result.

CONCLUSION

Given the results of this study, the aCGH was rarely determinant or decisive on the realization of a therapeutic abortion. These elements make us reflect on the necessity of maintaining this test before 14 weeks of gestation or propose it as a second-line test after the ultrasound shows signs at 18weeks of gestation.

Chromosomal Microarray Analysis versus Karyotyping in Fetuses with Increased Nuchal Translucency

We have carried out a retrospective study of chromosome anomalies associated with increased nuchal translucency (NT) in order to compare yield rates of karyotype, chromosome microarray analysis (CMA), and non-invasive prenatal testing (NIPT) in this condition. Presenting with increased NT or cystic hygroma ≥3.5 mm as an isolated sign, 249 fetuses underwent karyotype and/or CMA from 11 to 18 gestational weeks. Karyotype and fluorescence in situ hybridization (FISH) analyses detected 103 chromosomal anomalies including 95 aneuploidies and eight chromosomal rearrangements or derivatives. Further, seven pathogenic copy number variants (CNV), five likely pathogenic CNVs, and 15 variants of unknown significance (VOUS) were detected by CMA in fetuses with normal karyotype. Genetic testing is now facing new challenges due to results with uncertain clinical impacts. Additional investigations will be necessary to interpret these findings. More than 15% of the anomalies that we have diagnosed with invasive techniques could not be detected by NIPT. It is therefore definitely not recommended in the case of ultrasound anomalies. These results, while corroborating the use of CMA in fetuses with increased NT as a second tier after rapid aneuploidy testing, do not suggest a dismissal of karyotype analysis.

The importance of pre- and post-test counseling for prenatal cell-free DNA screening for common fetal aneuploidies

INTRODUCTION

Prenatal cell-free DNA screening for common fetal aneuploidies has rapidly changed the paradigm of prenatal care. Despite its advantages compared to conventional screening methods, its unexpectedly rapid implementation in clinical practice has generated several ethical and medical issues and misconceptions. Aggressive commercial marketing of cell-free DNA screening and media dissemination of misleading information have added confusion. Areas covered: This review provides an extensive update and will focus on the importance of pre-and post-test counseling for prenatal cell-free DNA screening not previously discussed extensively in the available literature. Additionally, we report cell-free DNA screening implementation in the largest obstetrical tertiary unit in Finland which is one of few countries that provides all prenatal screening methods free of charge for all women and has a very high uptake of first-trimester screening. This is not a systematical review, but rather a narrative overview which includes the most relevant and recent original publications and reviews covering this issue. Expert opinion: Despite being the most accurate method for screening of common fetal aneuploidies, the knowledge and counseling should be substantially improved. Cell-free DNA screening is not a replacement for diagnostic testing and its use in prenatal testing is complex and limited.

Factors associated with common and atypical chromosome abnormalities after positive combined first-trimester screening in Chinese women: a retrospective cohort study

BACKGROUND

When cell-free DNA (cfDNA) testing is used as a secondary screening tool following combined first-trimester screening (cFTS), cFTS is used to estimate the prior risk for chromosome abnormalities. This study aimed to assess the factors that are associated with common and atypical abnormalities following cFTS, including cFTS risk, advanced maternal age, increased nuchal translucency (NT) ≥3.5 mm, and abnormal levels of serum markers.

METHODS

We reviewed a historical cohort of 1855 Chinese women carrying singleton pregnancies with a positive cFTS [at a threshold of 1:250 for trisomy (T) 21 or 1:180 for T18] in one public hospital over a five-year period. All chromosome abnormalities were confirmed by invasive prenatal diagnosis (IPD) with karyotyping, with or without array comparative genomic hybridization. Using multivariable binary logistic regression analysis, we determined the parameters that were associated with common and atypical abnormalities.

RESULTS

Overall, the prevalence of common and atypical abnormalities was 6.2 and 1.2%, respectively, and the prevalence increased with the risk of T21 by cFTS. In pregnancies with a risk of T21 > 1 in 100, a high risk of both T21 and T18, an increased NT, or a pregnancy-associated plasma A (PAPP-A) level <  0.2 multiple of medians (MoM), the prevalence of common abnormalities was 12.2, 64.7, 25.5 and 33.8%, respectively, while that of atypical abnormalities was 1.6, 3.9, 4.2, and 7.4%, respectively. In the multivariable binary logistic regression analysis, out of these four factors, only two (increased NT and PAPP_A <  0.2 MoM) were significant predictors of common and atypical abnormalities, respectively. Of all positive cFTS pregnancies, 50.4% did not have any of these four factors, and the prevalence of common and atypical abnormalities was 1.1 and 0.6%, respectively. There were three atypical abnormalities, all of which were mosaicism, and they were detected among women with IPD alone. The ages of these women were ≥ 35 years. All three pregnancies were continued after proper counseling. After giving birth, only one child had mild abnormalities, while the other two were phenotypically normal.

CONCLUSIONS

Our study identified factors associated with common and atypical abnormalities after cFTS. These factors can be used to estimate the prior risk for these abnormalities to help with post-cFTS counseling in terms of choosing between cfDNA testing and IPD.

Chromosomal microarray analysis in pregnancies at risk for a molecular disorder

Objective: The aim of this study was to evaluate the utility of chromosomal microarray (CMA) in patients who were solely referred for molecular diagnosis.Methods: During a 2-year period, CMA was the patients' choice, whether to opt for it or not, for those at risk for fetal hemoglobin Bart's disease or β-thalassemia major who were referred for invasive prenatal diagnosis and had a normal fetal genotype. CytoScan 750 K array (Affymetrix Inc., Santa Clara, CA) was used for CMA. The CMA testing results were collected.Results: There were 184 patients, who had a normal genotypic result, opting CMA testing without an obvious indication for fetal karyotyping. The median maternal age was 29 years (range, 17-34); the median gestational age was 13 weeks (range, 11-20). In two out of 184 (1.1%) cases unexpected de novo pathogenic microdeletions were found: a 3.2 Mb 22q11.21 microdeletion and a 0.8 Mb 16p11.2 microdeletion.Conclusions: Pregnancies at risk for thalassemia can also benefit from performing CMA. This information might be a part of the contents in comprehensive pretest counseling for those who are referred for diagnostic testing due to a molecular disorder.

Effect of Cell-Free DNA Screening vs Direct Invasive Diagnosis on Miscarriage Rates in Women With Pregnancies at High Risk of Trisomy 21: A Randomized Clinical Trial

IMPORTANCE

Cell-free DNA (cfDNA) tests are increasingly being offered to women in the first trimester of pregnancies at a high risk of trisomy 21 to decrease the number of required invasive fetal karyotyping procedures and their associated miscarriages. The effect of this strategy has not been evaluated.

OBJECTIVE

To compare the rates of miscarriage following invasive procedures only in the case of positive cfDNA test results vs immediate invasive testing procedures (amniocentesis or chorionic villus sampling) in women with pregnancies at high risk of trisomy 21 as identified by first-trimester combined screening.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial conducted from April 8, 2014, to April 7, 2016, in 57 centers in France among 2111 women with pregnancies with a risk of trisomy 21 between 1 in 5 and 1 in 250 following combined first-trimester screening.

INTERVENTIONS

Patients were randomized to receive either cfDNA testing followed by invasive testing procedures only when cfDNA tests results were positive (n = 1034) or to receive immediate invasive testing procedures (n = 1017). The cfDNA testing was performed using an in-house validated method based on next-generation sequencing.

MAIN OUTCOMES AND MEASURES

The primary outcome was number of miscarriages before 24 weeks' gestation. Secondary outcomes included cfDNA testing detection rate for trisomy 21. The primary outcome underwent 1-sided testing; secondary outcomes underwent 2-sided testing.

RESULTS

Among 2051 women who were randomized and analyzed (mean age, 36.3 [SD, 5.0] years), 1997 (97.4%) completed the trial. The miscarriage rate was not significantly different between groups at 8 (0.8%) vs 8 (0.8%), for a risk difference of -0.03% (1-sided 95% CI, -0.68% to ∞; P = .47). The cfDNA detection rate for trisomy 21 was 100% (95% CI, 87.2%-100%).

CONCLUSIONS AND RELEVANCE

Among women with pregnancies at high risk of trisomy 21, offering cfDNA screening, followed by invasive testing if cfDNA test results were positive, compared with invasive testing procedures alone, did not result in a significant reduction in miscarriage before 24 weeks. The study may have been underpowered to detect clinically important differences in miscarriage rates.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02127515.

Prenatal diagnostic testing and atypical chromosome abnormalities following combined first-trimester screening: implications for contingent models of non-invasive prenatal testing

OBJECTIVES

To investigate by means of a population-based analysis of a cohort of women who underwent combined first-trimester screening (CFTS), changes in uptake of invasive prenatal diagnosis according to risk of trisomy 21 (T21) on CFTS, and prevalence and methods for ascertainment of atypical chromosome abnormalities.

METHODS

This was a retrospective cohort study using state-wide prenatal datasets from Victoria, Australia. A three-step approach was taken to analyze the data: (1) linkage of records between serum screening and diagnostic results; (2) comparison of rates of diagnostic testing according to CFTS T21 risk result category in a 2014-2015 cohort with those of a historical 2002-2004 cohort; (3) detailed analysis of atypical abnormalities in the 2014-2015 group according to CFTS T21 risk result, individual serum analyte level and other indications for invasive diagnostic testing.

RESULTS

In 2014-2015, there were 100 418 CFTS results issued for 146 776 births (68.4%). The overall prevalence of atypical chromosome abnormalities in the entire CFTS cohort was 0.10% and was highest in those with CFTS T21 risk > 1 in 10 (4.6%), or serum analyte levels < 0.2 multiples of the median (MoM) (6.9% for pregnancy-associated plasma protein-A (PAPP-A) and 5.2% for beta-human chorionic gonadotropin (β-hCG)). Almost half (49.2%) of women with PAPP-A < 0.2 MoM had a risk for T21 on CFTS of less than 1 in 100. The majority (55%) of atypical abnormalities occurred in women with CFTS T21 risk below 1 in 300, and were most commonly detected on ultrasound examination (47.1%).

CONCLUSION

Concerns regarding missed diagnoses of atypical chromosome abnormalities when non-invasive prenatal testing is offered after a result of high risk on CFTS can be mitigated if invasive diagnostic testing is offered to those women with CFTS T21 risk of > 1 in 100, serum PAPP-A or β-hCG < 0.2 MoM, or ultrasound-detected abnormality. This has implications for contingent models of screening. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.