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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. Key points: What's already known about this topic? Abnormal non‐invasive prenatal testing requires diagnostic testing to verify whether the chromosome anomaly is present in the fetus as well.Investigation of both uncultured and cultured amniotic fluid (AF) cells is necessary for accurate detection of true fetal mosaicism. What does this study add? The added value of investigating AF cell cultures in addition to uncultured cells is limited to two of 204 (1%) cases. In these cases, true fetal mosaicsm would otherwise be missed. [ABSTRACT FROM AUTHOR]

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. Key points: What's already known about this topic? CPM may have an impact on fetal growth and birthweight.CPM type 3 often involving a meiotic trisomy is associated with an adverse pregnancy outcome. What does this study add? Although fetal growth problems were more often seen in CPM type 3 and those involving a meiotic trisomy, both CPM type 1 and CPM involving a mitotic trisomy were also associated with an increased risk of impaired fetal growth and low birthweight.Irrespective of CPM type, trisomy origin, or involved chromosome aberration, we advocate to closely monitor all pregnancies where CPM is suspected, except for CPM type 2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Objective: Non‐invasive prenatal testing (NIPT) detects placental chromosome aberrations. When amniocentesis reveals a normal karyotype, confined placental mosaicism (CPM) may be assumed. In order to confirm this, placental cytogenetic studies were performed. Method: NIPT was conducted in the course of the Dutch TRIDENT study. Placentas of 10 cases with NIPT results indicating an autosomal trisomy and showing a normal (N = 9) or low mosaic karyotype (N = 1) in amniotic fluid (AF) were investigated. The cytotrophoblast as well as the mesenchymal core of two to four placental chorionic villi biopsies were studied with single nucleotide polymorphism (SNP) array. Clinical outcome data were collected. Results: In 10/10 cases, CPM was proven. In 3/10 cases trisomy/uniparental disomy (UPD)/biparental disomy (BPD) mosaicism was discovered. In 2/3 cases, all three cell lines were present in the placenta, whereas BPD was found in AF. In 1/3 cases trisomy 22/UPD22 was present in AF while trisomy 22/BPD22 mosaicism was found in the placenta. Five of 10 pregnancies were affected with pre‐eclampsia, low birth weight, preterm delivery, and/or congenital malformations. Conclusion: The presence of trisomy/UPD/BPD mosaicism in 3/10 cases that we investigated proves that trisomic zygote rescue may involve multiple rescue events during early embryogenesis. UPD mosaicism, when present in crucial fetal tissues, may explain the abnormal phenotype in undiagnosed cases. What's already known about this topic? Trisomic zygote rescue is the main mechanism for uniparental disomy (UPD) formation.Confined placental mosaicism (CPM) is the major source of discordant NIPT results.CPM is associated with a risk for adverse pregnancy outcome. What does this study add? Trisomic zygote rescue may involve multiple rescue events based on the co‐occurrence of a trisomy‐, UPD‐, and BPD‐cell line in half of the rescued cases as revealed by placental studies. [ABSTRACT FROM AUTHOR]

Background: Whole genome array testing not only provides an increased diagnostic yield of pathogenic causative findings, but it may also reveal so called susceptibility loci (SL) for neurodevelopmental disorders. The goal of this study was to evaluate the pregnancy outcomes in SL cases and to establish a protocol for pregnancy management, follow-up and additional investigations.Methods: Fifty seven cases were evaluated: 34 with and 23 without ultrasound anomalies at referral. Each pregnant couple received pretest counseling and extensive posttest genetic counseling.Results: After diagnosis of SL, parental testing and an additional ultrasound examination were offered. The severity of the ultrasound anomalies and not the diagnosis of SL was the most important factor contributing to the decision on pregnancy continuation. In the majority of cases with milder or no ultrasound anomalies, the pregnancy was continued and a normal outcome after birth was observed.Conclusions: The diagnosis of a SL did not seem to be a reason for termination of pregnancy. Most patients were able to cope with the uncertainty and were interested in both prenatal and postnatal actionability of SL. Long-term follow-up is crucial to assess the actual risks for neurodevelopmental disorders, especially in families with unremarkable history. © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

What's already known about this topic?The rare Guadalajara variant of G6PD deficiency is known for causing severe hemolytic anemia. What does this study add?This is the first published case of a diagnosed and treated fetal anemia, caused by the Guadalajara variant of G6PD deficiency.It is important to note that non‐invasive fetal Doppler screening can be performed for pregnant women who are carriers of this X‐linked recessive disorder. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]