The role of confined placental mosaicism in fetal growth restriction: A retrospective cohort study.

OBJECTIVE: To evaluate which cytogenetic characteristics of confined placental mosaicism (CPM) detected in the first trimester chorionic villi and/or placentas in terms of chromosome aberration, cell lineage involved and trisomy origin will lead to fetal growth restriction and low birthweight. METHODS: Cohort study using routinely collected perinatal data and cytogenetic data of non-invasive prenatal testing, the first trimester chorionic villi sampling and postnatal placentas. RESULTS: 215 CPM cases were found. Fetal growth restriction (FGR) and low birthweight below the 10th percentile (BW < p10) were seen in 34.0% and 23.1%, respectively. Excluding cases of trisomy 16, 29.1% showed FGR and 17.9% had a BW < p10. The highest rate of FGR and BW < p10 was found in CPM type 3, but differences with type 1 and 2 were not significant. FGR and BW < p10 were significantly more often observed in cases with meiotic trisomies. CONCLUSION: There is an association between CPM and FGR and BW < p10. This association is not restricted to trisomy 16, neither to CPM type 3, nor to CPM involving a meiotic trisomy. Pregnancies with all CPM types and origins should be considered to be at increased risk of FGR and low BW < p10. A close prenatal fetal monitoring is indicated in all cases of CPM.

Prenatal counseling of an isolated fetal small head circumference during the second trimester expert ultrasound examination.

OBJECTIVE: To evaluate perinatal and postnatal outcomes of fetuses with an isolated small head circumference (HC) on expert ultrasound examination in the second trimester for further recommendations in prenatal care. STUDY DESIGN: In a retrospective cohort we included singleton-pregnancies with a fetal HC > -3.0 SD and ≤ -1.64 SD determined on expert ultrasound examination between 18 and 24 weeks of gestational age. Three subgroups were determined: "isolated small HC (ISHC)", "small HC plus abdominal circumference (AC) ≤ p10 (SHC+)" and "small HC plus AC ≤ p10 and Doppler abnormalities (SHC + D)". After ultrasound examination, genetic testing was sometimes offered and postnatally genetic tests were performed on indication. RESULTS: We included 252 pregnancies: 109 ISHC, 104 SHC+, and 39 SHC + D. In the ISHC and SHC+ subgroup, 96 % of the fetuses were born alive and did not die neonatal. In the SH + D group this was only 38 %. In the SHC+ subgroup, less fetuses were delivered vaginal (non-instrumental) compared to the ISHC subgroup (61 % vs. 73 %, p < 0.01). In the ISHC and SHC+ subgroup s some fetuses were diagnosed with congenital defects (4 % vs. 10 %, p = 0.08) and with a genetic anomaly (6.4 % vs. 7.7 %, p = 0.13) after 24 weeks or postnatally. In SHC + D subgroups 5 % presented with congenital defects and 2.6 % with a genetic anomaly. CONCLUSION: We conclude that fetuses with a small HC without structural anomalies on second trimester expert ultrasound require follow-up and special medical attention. We recommend differentiating between ISHC, SHC+, and SHC + D for prenatal counseling. Genetic testing and referral to a clinical geneticist should be considered.

Limited additional value of karyotyping cultured amniotic fluid cell colonies in addition to microarray on uncultured cells for confirmation of abnormal non-invasive prenatal testing results.

OBJECTIVES: Non-invasive prenatal testing (NIPT) allows the detection of placental chromosome aberrations. To verify whether the fetus also has the chromosome aberration, diagnostic follow-up testing is required. The aim of this retrospective study was to assess the added value of analyzing amniotic fluid (AF) cell cultures in addition to uncultured AF cells for the detection of fetal mosaicism. METHOD: NIPT was performed as part of the Dutch TRIDENT study. Cytogenetic studies in uncultured AF were performed using single nucleotide polymorphism (SNP)-array. Cultured AF cell colonies (in situ method) were investigated with fluorescent in situ hybridization and/or karyotyping. Clinical outcome data were collected in cases with discordant results. RESULTS: Between April 2014 and December 2021, 368 amniocenteses were performed after a chromosomal aberration was detected with NIPT. Excluding 134 cases of common aneuploidies (confirmed by quantitative fluorescence polymerase chain reaction), 29 cases with investigation of uncultured cells only and 1 case without informed consent, 204 cases were eligible for this study. In 196 (96%) cases, the results in uncultured and cultured cells were concordant normal, abnormal or mosaic. Five cases (2%) showed mosaicism in cultured AF cells, whereas uncultured AF cells were normal. Two (1%) of these, one mosaic trisomy 13 and one mosaic trisomy 16, were considered true fetal mosaics. CONCLUSION: The added value of investigating AF cell cultures in addition to uncultured cells is limited to two of 204 (1%) cases in which true fetal mosaicsm would otherwise be missed. The clinical relevance of one (trisomy 13) remained unknown and the other case also showed ultrasound anomalies, which determined pregnancy management. This seems to justify limiting prenatal cytogenetic confirmatory testing to SNP arrays on uncultured AF cells, considerably shortening the reporting time.

The role of a multidisciplinary team in managing variants of uncertain clinical significance in prenatal genetic diagnosis.

BACKGROUND: Although in general prenatal exome sequencing only reports (likely) pathogenic variants, in some cases a variant of uncertain significance (VUS) is disclosed. The aims of this retrospective study were to evaluate the types of VUS that have been reported to prospective parents, possible reclassification and to design a standard flow chart to determine which types of VUS could be considered for reporting in prenatal settings. Furthermore, we investigated what the crucial elements are to facilitate rapid management of uncertain results in a prenatal setting. MATERIAL AND METHODS: We reviewed exome results from 451 pregnancies performed in 2019-2021. We analyzed which factors that were taken into account by the multidisciplinary team (MDT) contributed towards decision making on reporting VUS after prenatal exome sequencing. RESULTS: In 9/451 (2%) pregnancies tested with exome sequencing using a broad panel analysis a VUS was reported. After birth 3/9 VUS could be reclassified to likely pathogenic variants based on new clinical follow up data. We considered reporting VUS in genes: 1) matching the fetal phenotype, 2) associated with a severe disorder when a functional test is available or 3) possibly associated with a disorder where early post-partum diagnosis and treatment are crucial for a better prognosis. Two flowcharts were designed to guide first the laboratory specialist and then the MDT in decisions on reporting VUS. The crucial elements that enabled timely decisions on VUS disclosure were regular meetings, appropriate expertise, professional connections with other experts and psychological safety within the MDT. CONCLUSION: In this study three out of nine VUS could be re-classified as likely pathogenic after clinical follow-up. In order to protect pregnant couples from the burden of uncertain results, the genetic professionals have to take the responsibility to limit the reporting of VUS. This can be done not only by automated filtering of data, by following professional guidelines and by building standardized decision flows, but also by discussing individual cases considering personal situations and the involved disease and by sharing professional experience and responsibility in a multidisciplinary prenatal team setting.

What proportion of couples with a history of recurrent pregnancy loss and with a balanced rearrangement in one parent can potentially be identified through cell-free DNA genotyping?

BACKGROUND: Balanced chromosome aberrations are reported in about 1:30 couples with recurrent pregnancy loss (RPL). Karyotyping of both parents is necessary to identify these aberrations. Genome-wide non-invasive prenatal testing (NIPT) in case of recurrent pregnancy loss could be a more efficient way to identify couples at increased risk for carrying a balanced chromosome rearrangement. The aim of this study was to evaluate whether the potential fetal imbalances caused by parental balanced aberrations detected in our center are large enough to be detectable by genome-wide non-invasive prenatal testing (NIPT). MATERIAL AND METHODS: From January 1970 until May 2020 our laboratory received 30,863 unique requests for karyotyping due to RPL. We have identified 16,045 couples and evaluated all abnormal cytogenetic results to assess the minimal size of the involved chromosomal segments in potential unbalanced products of the rearrangements. RESULTS: In the presented cohort we detected 277 aberrant balanced translocations/inversions in females and 185 in males amongst 16,045 couples with RPL, which can be translated to a risk of 1:35 (2.9%, 95% CI 2.6-3.2%). Our study showed that the vast majority (98.7%, 95% CI 97.1-99.5%) of these balanced aberrations will potentially cause a fetal imbalance > 10 Mb, which is detectable with genome-wide NIPT if it was performed during one of the miscarriages. CONCLUSIONS: Our study suggests that genome-wide NIPT is able to reveal most unbalanced products of balanced chromosomal rearrangements carried by couples with RPL and therefore can potentially identify balanced chromosomal aberration carriers. Moreover, our data suggest that these couples can be offered NIPT in case they decline invasive testing in future pregnancies.

Liquid Biopsies for Colorectal Cancer and Advanced Adenoma Screening and Surveillance: What to Measure?

Colorectal cancer (CRC) colonoscopic surveillance is effective but burdensome. Circulating tumor DNA (ctDNA) analysis has emerged as a promising, minimally invasive tool for disease detection and management. Here, we assessed which ctDNA assay might be most suitable for a ctDNA-based CRC screening/surveillance blood test. In this prospective, proof-of-concept study, patients with colonoscopies for Lynch surveillance or the National Colorectal Cancer screening program were included between 7 July 2019 and 3 June 2022. Blood was drawn, and if advanced neoplasia (adenoma with villous component, high-grade dysplasia, ≥10 mm, or CRC) was detected, it was analyzed for chromosomal copy number variations, single nucleotide variants, and genome-wide methylation (MeD-seq). Outcomes were compared with corresponding patients' tissues and the MeD-seq results of healthy blood donors. Two Lynch carriers and eight screening program patients were included: five with CRC and five with advanced adenomas. cfDNA showed copy number variations and single nucleotide variants in one patient with CRC and liver metastases. Eight patients analyzed with MeD-seq showed clustering of Lynch-associated and sporadic microsatellite instable lesions separate from microsatellite stable lesions, as did healthy blood donors. In conclusion, whereas copy number changes and single nucleotide variants were only detected in one patient, cfDNA methylation profiles could discriminate all microsatellite instable advanced neoplasia, rendering this tool particularly promising for LS surveillance. Larger studies are warranted to validate these findings.

Challenges and Pragmatic Solutions in Pre-Test and Post-Test Genetic Counseling for Prenatal Exome Sequencing.

The yield of genetic prenatal diagnosis has been notably improved by introducing whole genome chromosomal microarray (CMA) and prenatal exome sequencing (pES). However, together with increased numbers of diagnoses made, the need to manage challenging findings such as variants of unknown significance (VUS) and incidental findings (IF) also increased. We have summarized the current guidelines and recommendations and we have shown current solutions used in our tertiary center in the Netherlands. We discuss four of the most common clinical situations: fetus with normal pES results, fetus with a pathogenic finding explaining the fetal phenotype, fetus with a variant of uncertain clinical significance fitting the phenotype and fetus with a variant leading to an incidental diagnosis. Additionally, we reflect on solutions in order to facilitate genetic counseling in an NGS-era.

An 8q24 Gain in Pancreatic Juice Is a Candidate Biomarker for the Detection of Pancreatic Cancer.

Secretin-stimulated pancreatic juice (PJ), collected from the duodenum, presents a valuable biomarker source for the (earlier) detection of pancreatic cancer (PC). Here, we evaluate the feasibility and performance of shallow sequencing to detect copy number variations (CNVs) in cell-free DNA (cfDNA) from PJ for PC detection. First, we confirmed the feasibility of shallow sequencing in PJ (n = 4), matched plasma (n = 3) and tissue samples (n = 4, microarray). Subsequently, shallow sequencing was performed on cfDNA from PJ of 26 cases (25 sporadic PC, 1 high-grade dysplasia) and 19 controls with a hereditary or familial increased risk of PC. 40 of the 45 PJ samples met the quality criteria for cfDNA analysis. Nine individuals had an 8q24 gain (oncogene MYC; 23%; eight cases (33%) and one control (6%), p = 0.04); six had both a 2q gain (STAT1) and 5p loss (CDH10; 15%; four cases (7%) and two controls (13%), p = 0.72). The presence of an 8q24 gain differentiated the cases and controls, with a sensitivity of 33% (95% CI 16-55%) and specificity of 94% (95% CI 70-100%). The presence of either an 8q24 or 2q gain with a 5p loss was related to a sensitivity of 50% (95% CI 29-71%) and specificity of 81% (95% CI 54-96%). Shallow sequencing of PJ is feasible. The presence of an 8q24 gain in PJ shows promise as a biomarker for the detection of PC. Further research is required with a larger sample size and consecutively collected samples in high-risk individuals prior to implementation in a surveillance cohort.

Prenatal ultrasound finding of atypical genitalia: Counseling, genetic testing and outcomes.

OBJECTIVE: To report uptake of genetic counseling (GC) and prenatal genetic testing after the finding of atypical genitalia on prenatal ultrasound (US) and the clinical and genetic findings of these pregnancies. METHODS: A retrospective cohort study (2017-2019) of atypical fetal genitalia in a large expert center for disorders/differences of sex development. We describe counseling aspects, invasive prenatal testing, genetic and clinical outcome of fetuses apparently without [group 1, n = 22 (38%)] or with [group 2, n = 36 (62%)] additional anomalies on US. RESULTS: In group 1, 86% of parents opted for GC versus 72% in group 2, and respectively 58% and 15% of these parents refrained from invasive testing. Atypical genitalia were postnatally confirmed in 91% (group 1) and 64% (group 2), indicating a high rate of false positive US diagnosis of ambiguous genitalia. Four genetic diagnoses were established in group 1 (18%) and 10 in group 2 (28%). The total genetic diagnostic yield was 24%. No terminations of pregnancy occurred in group 1. CONCLUSIONS: For optimal care, referral for an expert fetal US scan, GC and invasive diagnostics including broad testing should be offered after prenatal detection of isolated atypical genitalia.

Clinical impact of additional findings detected by genome-wide non-invasive prenatal testing: Follow-up results of the TRIDENT-2 study.

In the TRIDENT-2 study, all pregnant women in the Netherlands are offered genome-wide non-invasive prenatal testing (GW-NIPT) with a choice of receiving either full screening or screening solely for common trisomies. Previous data showed that GW-NIPT can reliably detect common trisomies in the general obstetric population and that this test can also detect other chromosomal abnormalities (additional findings). However, evidence regarding the clinical impact of screening for additional findings is lacking. Therefore, we present follow-up results of the TRIDENT-2 study to determine this clinical impact based on the laboratory and perinatal outcomes of cases with additional findings. Between April 2017 and April 2019, additional findings were detected in 402/110,739 pregnancies (0.36%). For 358 cases, the origin was proven to be either fetal (n = 79; 22.1%), (assumed) confined placental mosaicism (CPM) (n = 189; 52.8%), or maternal (n = 90; 25.1%). For the remaining 44 (10.9%), the origin of the aberration could not be determined. Most fetal chromosomal aberrations were pathogenic and associated with severe clinical phenotypes (61/79; 77.2%). For CPM cases, occurrence of pre-eclampsia (8.5% [16/189] vs 0.5% [754/159,924]; RR 18.5), and birth weight <2.3rd percentile (13.6% [24/177] vs 2.5% [3,892/155,491]; RR 5.5) were significantly increased compared to the general obstetric population. Of the 90 maternal findings, 12 (13.3%) were malignancies and 32 (35.6%) (mosaic) pathogenic copy number variants, mostly associated with mild or no clinical phenotypes. Data from this large cohort study provide crucial information for deciding if and how to implement GW-NIPT in screening programs. Additionally, these data can inform the challenging interpretation, counseling, and follow-up of additional findings.

Noninvasive Prenatal Test Results Indicative of Maternal Malignancies: A Nationwide Genetic and Clinical Follow-Up Study.

PURPOSE: Noninvasive prenatal testing (NIPT) for fetal aneuploidy screening using cell-free DNA derived from maternal plasma can incidentally raise suspicion for cancer. Diagnostic routing after malignancy suspicious-NIPT faces many challenges. Here, we detail malignancy suspicious-NIPT cases, and describe the clinical characteristics, chromosomal aberrations, and diagnostic routing of the patients with a confirmed malignancy. Clinical lessons can be learned from our experience. METHODS: Patients with NIPT results indicative of a malignancy referred for tumor screening between April 2017 and April 2020 were retrospectively included from a Dutch nationwide NIPT implementation study, TRIDENT-2. NIPT profiles from patients with confirmed malignancies were reviewed, and the pattern of chromosomal aberrations related to tumor type was analyzed. We evaluated the diagnostic contribution of clinical and genetic examinations. RESULTS: Malignancy suspicious-NIPT results were reported in 0.03% after genome-wide NIPT, and malignancies confirmed in 16 patients (16/48, 33.3%). Multiple chromosomal aberrations were seen in 23 of 48 patients with genome-wide NIPT, and a malignancy was confirmed in 16 patients (16/23, 69.6%). After targeted NIPT, 0.005% malignancy suspicious-NIPT results were reported, in 2/3 patients a malignancy was confirmed. Different tumor types and stages were diagnosed, predominantly hematologic malignancies (12/18). NIPT data showed recurrent gains and losses in primary mediastinal B-cell lymphomas and classic Hodgkin lymphomas. Magnetic resonance imaging and computed tomography were most informative in diagnosing the malignancy. CONCLUSION: In 231,896 pregnant women, a low percentage (0.02%) of NIPT results were assessed as indicative of a maternal malignancy. However, when multiple chromosomal aberrations were found, the risk of a confirmed malignancy was considerably high. Referral for extensive oncologic examination is recommended, and may be guided by tumor-specific hallmarks in the NIPT profile.

Non-invasive prenatal diagnosis for translocation carriers-YES please or NO go?

INTRODUCTION: The presence of an unbalanced familial translocation can be reliably assessed in the cytotrophoblast of chorionic villi. However, carriers of a balanced translocation often decline invasive testing. This study aimed to investigate whether an unbalanced translocation can also be diagnosed in cell free DNA by whole-genome non-invasive prenatal screening (NIPS). MATERIAL AND METHODS: Pregnant women carrying a fetus with an unbalanced familial translocation, for whom NIPS as well as microarray data were available, were included in this retrospective assessment. NIPS was performed in the course of the TRIDENT study. RESULTS: In 12 cases, both NIPS and microarray data were available. In 10 of 12 cases the unbalanced translocation was correctly identified by NIPS without prior knowledge on parental translocation. One was missed because the fetal fraction was too low. One was missed because of technical restrictions in calling 16p gains. CONCLUSIONS: This study supports the hypothesis that routine NIPS may be used for prenatal diagnosis of unbalanced inheritance of familial translocations, especially with prior knowledge of the translocation allowing focused examination of the involved chromosomal regions. Our study showed that routine shallow sequencing designed for aneuploidy detection in cell free DNA may be sufficient for higher resolution NIPS, if specialized copy number software is used and if sufficient fetal fraction is present.

How to deal with uncertainty in prenatal genomics: A systematic review of guidelines and policies.

Exome sequencing (ES) enhanced the diagnostic yield of genetic testing, but has also increased the possibility of uncertain findings. Prenatal ES is increasingly being offered after a fetal abnormality is detected through ultrasound. It is important to know how to handle uncertainty in this particularly stressful period. This systematic review aimed to provide a comprehensive overview of guidelines available for addressing uncertainty related to prenatal chromosomal microarray (CMA) and ES. Ten uncertainty types associated with prenatal ES and CMA were identified and defined by an international multidisciplinary team. Medline (all) and Embase were systematically searched. Laboratory scientists, clinical geneticists, psychologists, and a fetal medicine specialist screened the papers and performed the data extraction. Nineteen papers were included. Recommendations generally emphasized the importance of trio analysis, clinical information, data sharing, validation and re-analysis, protocols, multidisciplinary teams, genetic counselling, whether to limit the possible scope of results, and when to report particular findings. This systematic review helps provide a vocabulary for uncertainties, and a compass to navigate uncertainties. Prenatal CMA and ES guidelines provide a strong starting point for determining how to handle uncertainty. Gaps in guidelines and recommendations were identified and discussed to provide direction for future research and policy making.

The potential diagnostic yield of whole exome sequencing in pregnancies complicated by fetal ultrasound anomalies.

INTRODUCTION: The aim of this retrospective cohort study was to determine the potential diagnostic yield of prenatal whole exome sequencing in fetuses with structural anomalies on expert ultrasound scans and normal chromosomal microarray results. MATERIAL AND METHODS: In the period 2013-2016, 391 pregnant women with fetal ultrasound anomalies who received normal chromosomal microarray results, were referred for additional genetic counseling and opted for additional molecular testing pre- and/or postnatally. Most of the couples received only a targeted molecular test and in 159 cases (40.7%) whole exome sequencing (broad gene panels or open exome) was performed. The results of these molecular tests were evaluated retrospectively, regardless of the time of the genetic diagnosis (prenatal or postnatal). RESULTS: In 76 of 391 fetuses (19.4%, 95% CI 15.8%-23.6%) molecular testing provided a genetic diagnosis with identification of (likely) pathogenic variants. In the majority of cases (91.1%, 73/76) the (likely) pathogenic variant would be detected by prenatal whole exome sequencing analysis. CONCLUSIONS: Our retrospective cohort study shows that prenatal whole exome sequencing, if offered by a clinical geneticist, in addition to chromosomal microarray, would notably increase the diagnostic yield in fetuses with ultrasound anomalies and would allow early diagnosis of a genetic disorder irrespective of the (incomplete) fetal phenotype.

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.

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.

TRIDENT-2: National Implementation of Genome-wide Non-invasive Prenatal Testing as a First-Tier Screening Test in the Netherlands.

The Netherlands launched a nationwide implementation study on non-invasive prenatal testing (NIPT) as a first-tier test offered to all pregnant women. This started on April 1, 2017 as the TRIDENT-2 study, licensed by the Dutch Ministry of Health. In the first year, NIPT was performed in 73,239 pregnancies (42% of all pregnancies), 7,239 (4%) chose first-trimester combined testing, and 54% did not participate. The number of trisomies 21 (239, 0.33%), 18 (49, 0.07%), and 13 (55, 0.08%) found in this study is comparable to earlier studies, but the Positive Predictive Values (PPV)-96% for trisomy 21, 98% for trisomy 18, and 53% for trisomy 13-were higher than expected. Findings other than trisomy 21, 18, or 13 were reported on request of the pregnant women; 78% of women chose to have these reported. The number of additional findings was 207 (0.36%); these included other trisomies (101, 0.18%, PPV 6%, many of the remaining 94% of cases are likely confined placental mosaics and possibly clinically significant), structural chromosomal aberrations (95, 0.16%, PPV 32%,) and complex abnormal profiles indicative of maternal malignancies (11, 0.02%, PPV 64%). The implementation of genome-wide NIPT is under debate because the benefits of detecting other fetal chromosomal aberrations must be balanced against the risks of discordant positives, parental anxiety, and a potential increase in (invasive) diagnostic procedures. Our first-year data, including clinical data and laboratory follow-up data, will fuel this debate. Furthermore, we describe how NIPT can successfully be embedded into a national screening program with a single chain for prenatal care including counseling, testing, and follow-up.

Placental studies elucidate discrepancies between NIPT showing a structural chromosome aberration and a differently abnormal fetal karyotype.

OBJECTIVE: Placental cytogenetic studies may reveal the origin of discordant noninvasive prenatal testing (NIPT). We performed placental studies to elucidate discordances between NIPT showing a structural chromosome aberration and the fetus having a different chromosome aberration in three cases. METHOD: Diagnostic testing with genomic SNP microarray was performed in three cases with NIPT showing a duplication on 4q (case 1), a terminal deletion of 13q (case 2), and a terminal deletion of 15q (case 3). Placental studies involved SNP array analysis of cytotrophoblast and mesenchymal core of chorionic villi of four placental quadrants. Clinical follow-up was performed as well. RESULTS: Amniotic fluid revealed a different structural chromosome aberration than predicted by NIPT: a terminal 2q deletion (case 1), a segmental uniparental isodisomy of 13q (case 2), and a terminal duplication of 15q and of 13q (case 3). Placental studies revealed the aberration detected with NIPT in the cytotrophoblast, whereas the fetal karyotype was confirmed in the placental mesenchymal core. CONCLUSION: Our study shows that targeted cytogenetic investigations for confirmation of NIPT showing a microscopically visible structural chromosome aberration should be avoided, since another aberration, even a submicroscopic one or one involving another chromosome, may be present in the fetus.