Mosaic trisomy 16: what are the obstetric and long-term childhood outcomes?

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.

Mosaic trisomy 16 at amniocentesis in a pregnancy associated with positive non-invasive prenatal testing for trisomy 16, placental trisomy 16, intrauterine growth restriction, intrauterine fetal death, cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, and prenatal progressive decrease of the aneuploid cell line

OBJECTIVE

We present mosaic trisomy 16 at amniocentesis in a pregnancy associated with positive non-invasive prenatal testing (NIPT) for trisomy 16, placental trisomy 16, intrauterine growth restriction (IUGR), intrauterine fetal death (IUFD), cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes and uncultured amniocytes, and prenatal progressive decrease of the aneuploid cell line.

CASE REPORT

A 26-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of positive NIPT for trisomy 16 at 12 weeks of gestation. Amniocentesis revealed a karyotype of 47,XX,+16 [10]/46,XX[17], and simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (16) × 3 [0.43] consistent with 43% mosaicism for trisomy 16. She was referred for genetic counseling at 19 weeks of gestation, and a fetus with IUGR was noted to have a size equivalent to 16 weeks of gestation. At 23 weeks of gestation, the fetus manifested oligohydramnios, fetal cardiomegaly and severe IUGR (fetal size equivalent to 20 weeks of gestation). Repeat amniocentesis revealed a karyotype of 46,XX (20/20 colonies) in cultured amniocytes and mosaic trisomy 16 by aCGH in uncultured amniocytes. aCGH analysis on uncultured amniocytes revealed the result of arr 16p13.3q24.3 × 2.3, consistent with 30% (log2 ratio = 0.2) mosaicism for trisomy 16. Quantitative fluorescence polymerase chain reaction (QF-PCR) assays on the DNA extracted from parental bloods and uncultured amniocytes excluded uniparental disomy (UPD) 16. The parental karyotypes were normal. IUFD was noted at amniocentesis. The pregnancy was subsequently terminated, and a 288-g female fetus was delivered with no phenotypic abnormalities. The umbilical cord had a karyotype of 46,XX (40/40 cells), and the placenta had a karyotype of 47,XX,+16 (40/40 cells). QF-PCR assays of the placenta confirmed a maternal origin of trisomy 16.

CONCLUSION

Mosaic trisomy 16 at amniocentesis can be associated with positive NIPT for trisomy 16, placental trisomy 16, IUGR, IUFD, cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, and prenatal progressive decrease of the aneuploid cell line.

Chromosomal Numerical Aberrations and Rare Copy Number Variation in Patients with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Inflammatory bowel diseases [IBD] have a complex polygenic aetiology. Rare genetic variants can cause monogenic intestinal inflammation. The impact of chromosomal aberrations and large structural abnormalities on IBD susceptibility is not clear. We aimed to comprehensively characterise the phenotype and prevalence of patients with IBD who possess rare numerical and structural chromosomal abnormalities.

METHODS

We performed a systematic literature search of databases PubMed and Embase; and analysed gnomAD, Clinvar, the 100 000 Genomes Project, and DECIPHER databases. Further, we analysed international paediatric IBD cohorts to investigate the role of IL2RA duplications in IBD susceptibility.

RESULTS

A meta-analysis suggests that monosomy X [Turner syndrome] is associated with increased expressivity of IBD that exceeds the population baseline (1.86%, 95% confidence interval [CI] 1.48 to 2.34%) and causes a younger age of IBD onset. There is little evidence that Klinefelter syndrome, Trisomy 21, Trisomy 18, mosaic Trisomy 9 and 16, or partial trisomies contribute to IBD susceptibility. Copy number analysis studies suggest inconsistent results. Monoallelic loss of X-linked or haploinsufficient genes is associated with IBD by hemizygous or heterozygous deletions, respectively. However, haploinsufficient gene deletions are detected in healthy reference populations, suggesting that the expressivity of IBD might be overestimated. One duplication that has previously been identified as potentially contributing to IBD risk involves the IL2RA/IL15R loci. Here we provide additional evidence that a microduplication of this locus may predispose to very-early-onset IBD by identifying a second case in a distinct kindred. However, the penetrance of intestinal inflammation in this genetic aberration is low [<2.6%].

CONCLUSIONS

Turner syndrome is associated with increased susceptibility to intestinal inflammation. Duplication of the IL2RA/IL15R loci may contribute to disease risk.

Rare autosomal trisomies detected by non-invasive prenatal testing: an overview of current knowledge

Non-invasive prenatal testing has been introduced for the detection of Trisomy 13, 18, and 21. Using genome-wide screening also other "rare" autosomal trisomies (RATs) can be detected with a frequency about half the frequency of the common trisomies in the large population-based studies. Large prospective studies and clear clinical guidelines are lacking to provide adequate counseling and management to those who are confronted with a RAT as a healthcare professional or patient. In this review we reviewed the current knowledge of the most common RATs. We compiled clinical relevant parameters such as incidence, meiotic or mitotic origin, the risk of fetal (mosaic) aneuploidy, clinical manifestations of fetal mosaicism for a RAT, the effect of confined placental mosaicism on placental function and the risk of uniparental disomy (UPD). Finally, we identified gaps in the knowledge on RATs and highlight areas of future research. This overview may serve as a first guide for prenatal management for each of these RATs.

Pregnancy outcome of confined placental mosaicism: meta-analysis of cohort studies

OBJECTIVE

This study aimed to assess the rate of adverse obstetrical and neonatal outcomes in pregnancies diagnosed with confined placental mosaicism relative to that of unaffected controls.

DATA SOURCES

Web-based databases were searched using relevant key words, and articles published from 1980 to February 2022 were retrieved.

STUDY ELIGIBILITY CRITERIA

Observational studies in English language including ≥10 cases of singleton pregnancies with diagnosis of confined placental mosaicism were included. The diagnosis was established after detection of any chromosomal abnormality at chorionic villus sampling for any indication, followed by normal karyotype from amniotic fluid or neonatal leukocyte culture.

METHODS

Two authors independently screened the references for eligibility, data extraction, and assessment of methodological quality using the Newcastle-Ottawa scale. All available obstetrical and neonatal outcomes were recorded. Random-effect meta-analysis was performed to estimate pooled odds ratios and 95% confidence intervals of available outcomes in pregnancies with and without confined placental mosaicism. Statistical heterogeneity was evaluated with I2 statistics (International Prospective Register of Systematic Reviews registration number: CRD42021260319).

RESULTS

Of the 80 articles reviewed, 8 retrospective matched-cohort studies (708 cases of confined placental mosaicism and 11,599 unaffected controls) compared cases with and without confined placental mosaicism and were included in the meta-analysis. The risk of delivering small-for-gestational-age neonates was significantly increased in confined placental mosaicism pregnancies according to crude analysis (odds ratio, 2.45; 95% confidence interval, 1.23-4.89; I2=72%) and to sensitivity analysis of high-quality studies (odds ratio, 3.65; 95% confidence interval, 2.43-5.57; I2=0%). Similarly, confined placental mosaicism resulted in an increased risk of birthweight below the third centile (odds ratio, 5.33; 95% confidence interval, 1.19-24.19; I2= 83%). Subgroup analysis revealed that the risk of delivering small-for-gestational-age neonates was 3-fold higher for confined placental mosaicism excluding trisomy 16, and 11-fold higher for cases including trisomy 16 only vs unaffected controls, respectively. No difference was found in the risk of low birthweight and preterm birth (at <37 weeks' gestation). Other outcomes were insufficiently reported, therefore they were not analyzed.

CONCLUSION

Pregnant women prenatally diagnosed with confined placental mosaicism have an increased risk of impaired fetal growth, suggesting the need for intensified antenatal surveillance.

Genome-Wide Cell-Free DNA Test for Fetal Chromosomal Abnormalities and Variants: Unrestricted Versus Restricted Reporting

This study aimed to compare the screening performance of genome-wide cfDNA testing for chromosomal abnormalities between two periods where additional findings were reported and not reported. Data were obtained from consecutive pregnant women with a singleton pregnancy at ≥10 weeks who requested cfDNA testing during 2015–2019. The performance of screening of the cfDNA test was determined by calculating the concordance rate, detection rate, and false-positive rate. Data from 3981 women were included. The no-result rates were similar between the two reporting periods (2.04% vs. 2.08%). Concordance rates for trisomy 21 and 18 were 100% and 100%, respectively. There were two cases tested high risk for trisomy 13, with a concordance rate of 0%. In total, 12 cases were high risk for any sex chromosome aneuploidy with an overall concordance of 75%, and 15 cases tested high risk for any rare autosomal trisomy, with a 13.3% concordance rate. The detection rates for trisomy 21 and 18 were 100% and 100%, respectively. For any SCA, the detection rate was 90%. For the two reporting periods, the combined false-positive rates were 0.93% and 0.17%, which were significantly different (p = 0.002). Restricting the reporting of additional findings from genome-wide cfDNA analysis has reduced the false-positive rate but without a reduction in the no-result rate.

Detection of Embryonic Trisomy 21 in the First Trimester Using Maternal Plasma Cell-Free RNA

Prenatal trisomy 21 (T21) screening commonly involves testing a maternal blood sample for fetal DNA aneuploidy. It is reliable but poses a cost barrier to universal screening. We hypothesized maternal plasma RNA screening might provide similar reliability but at a lower cost. Discovery experiments used plasma cell-free RNA from 20 women 11−13 weeks tested by RNA and miRNA microarrays followed by qRT-PCR. Thirty-six mRNAs and 18 small RNAs of the discovery cDNA were identified by qPCR as potential markers of embryonic T21. The second objective was validation of the RNA predictors in 998 independent pregnancies at 11−13 weeks including 50 T21. Initial analyses identified 9−15 differentially expressed RNA with modest predictive power (AUC < 0.70). The 54 RNAs were then subjected to machine learning. Eleven algorithms were trained on one partition and tested on an independent partition. The three best algorithms were identified by Kappa score and the effects of training/testing partition size and dataset class imbalance on prediction were evaluated. Six to ten RNAs predicted T21 with AUCs up to 1.00. The findings suggest that maternal plasma collected at 11−13 weeks, tested by qRT-PCR, and classified by machine learning, may accurately predict T21 for a lower cost than plasma DNA, thus opening the door to universal screening.

Identification of differentially methylated genes in first-trimester placentas with trisomy 16

The presence of an extra chromosome in the embryo karyotype often dramatically affects the fate of pregnancy. Trisomy 16 is the most common aneuploidy in first-trimester miscarriages. The present study identified changes in DNA methylation in chorionic villi of miscarriages with trisomy 16. Ninety-seven differentially methylated sites in 91 genes were identified (false discovery rate (FDR) < 0.05 and Δβ > 0.15) using DNA methylation arrays. Most of the differentially methylated genes encoded secreted proteins, signaling peptides, and receptors with disulfide bonds. Subsequent analysis using targeted bisulfite massive parallel sequencing showed hypermethylation of the promoters of specific genes in miscarriages with trisomy 16 but not miscarriages with other aneuploidies. Some of the genes were responsible for the development of the placenta and embryo (GATA3-AS1, TRPV6, SCL13A4, and CALCB) and the formation of the mitotic spindle (ANKRD53). Hypermethylation of GATA3-AS1 was associated with reduced expression of GATA3 protein in chorionic villi of miscarriages with trisomy 16. Aberrant hypermethylation of genes may lead to a decrease in expression, impaired trophoblast differentiation and invasion, mitotic disorders, chromosomal mosaicism and karyotype self-correction via trisomy rescue mechanisms.

Prenatal diagnosis of mosaic trisomy 16 by amniocentesis in a pregnancy associated with abnormal first-trimester screening result (low PAPP-A and low PlGF), intrauterine growth restriction and a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaic trisomy 16 by amniocentesis in a pregnancy associated with an abnormal first-trimester screening result, intrauterine growth restriction (IUGR) and a favorable outcome.

CASE REPORT

A 27-year-old woman underwent amniocentesis at 18 weeks of gestation because of an abnormal first-trimester screening result with maternal serum free β-hCG of 1.474 multiples of the median (MoM), pregnancy associated plasma protein-A (PAPP-A) of 0.122 MoM and placental growth factor (PlGF) of 0.101 MoM, and a Down syndrome risk of 1/45. Amniocentesis revealed a karyotype of 47,XY,+16 [9]/46,XY [16] and an abnormal array comparative genomic hybridization (aCGH) result of arr (16) × 3 [0.54] compatible with 54% mosaicism for trisomy 16 in uncultured amniocytes. At 24 weeks of gestation, repeat amniocentesis revealed a karyotype of 47,XY,+16 [4]/46,XY [16] and an aCGH result of arr 16p13.3q24.3 (96,766-90,567,357) × 2.25 with a log₂ ratio = 0.2 compatible with 20-30% mosaicism for trisomy 16 in uncultured amniocytes. Quantitative fluorescent polymerase chain reaction (QF-PCR) excluded uniparental disomy (UPD) 16. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 19.4% (12/62 cells) mosaic trisomy 16. Prenatal ultrasound revealed IUGR. At 36 weeks of gestation, a phenotypically normal baby was delivered with a body weight of 1900 g. The cord blood had a karyotype of 46,XY. QF-PCR analysis confirmed biparentally inherited disomy 16 in the cord blood and maternal-origin of trisomy 16 in the placenta. When follow-up at age two months, FISH analysis on 101 buccal mucosal cells and 32 urinary cells revealed no signal of trisomy 16.

CONCLUSION

Mosaic trisomy 16 at amniocentesis can be associated with IUGR and an abnormal first-trimester screening result with low PAPP-A and low PlGF. Mosaic trisomy 16 without UPD 16 at amniocentesis can have a favorable outcome, and the abnormal triosmy 16 cell line may disappear after birth.

Mouse models of aneuploidy to understand chromosome disorders

An organism or cell carrying a number of chromosomes that is not a multiple of the haploid count is in a state of aneuploidy. This condition results in significant changes in the level of expression of genes that are gained or lost from the aneuploid chromosome(s) and most cases in humans are not compatible with life. However, a few aneuploidies can lead to live births, typically associated with deleterious phenotypes. We do not understand why phenotypes arise from aneuploid syndromes in humans. Animal models have the potential to provide great insight, but less than a handful of mouse models of aneuploidy have been made, and no ideal system exists in which to study the effects of aneuploidy per se versus those of raised gene dosage. Here, we give an overview of human aneuploid syndromes, the effects on physiology of having an altered number of chromosomes and we present the currently available mouse models of aneuploidy, focusing on models of trisomy 21 (which causes Down syndrome) because this is the most common, and therefore, the most studied autosomal aneuploidy. Finally, we discuss the potential role of carrying an extra chromosome on aneuploid phenotypes, independent of changes in gene dosage, and methods by which this could be investigated further.

Outcomes of pregnancies with trisomy 16 mosaicism detected by NIPT: a series of case reports

Background

Trisomy 16 (T16) is thought to be the most frequent chromosome abnormality at conception, which is often associated with a high risk of abnormal outcomes.

Methods

A retrospective analysis of 14 cases with high risk of T16 by noninvasive prenatal testing (NIPT) was conducted. All cases in the analysis involved prenatal diagnosis, karyotyping and chromosomal microarray analysis.

Case reports

NIPT detected 12 cases of T16 and 2 cases of T16 mosaicism. Prenatal diagnosis confirmed 5 true positive cases and 9 false positive cases. Among the 5 true positive cases, 3 cases had ultrasound abnormalities. All of the 9 false positive cases continued their pregnancies. The newborns who were from these 9 false positive cases except 1 case (case 7) had low birth weights (< 2.5 kg) and there were also 2 premature deliveries.

Conclusion

NIPT serves as a fast and early prenatal screening method, giving clues to chromosome abnormalities and providing guidance for managing pregnancy. Confined placental mosaicism in 16 pregnancies may be at higher risk for preterm delivery.

Chromosomal mosaicism: Origins and clinical implications in preimplantation and prenatal diagnosis

The diagnosis of chromosomal mosaicism in the preimplantation and prenatal stage is fraught with uncertainty and multiple factors need to be considered in order to gauge the likely impact. The clinical effects of chromosomal mosaicism are directly linked to the type of the imbalance (size, gene content, and copy number), the timing of the initial event leading to mosaicism during embryogenesis/fetal development, the distribution of the abnormal cells throughout the various tissues within the body as well as the ratio of normal/abnormal cells within each of those tissues. Additional factors such as assay noise and culture artifacts also have an impact on the significance and management of mosaic cases. Genetic counseling is an important part of educating patients about the likelihood of having a liveborn with a chromosome abnormality and these risks differ according to the time of ascertainment and the tissue where the mosaic cells were initially discovered. Each situation needs to be assessed on a case-by-case basis and counseled accordingly. This review will discuss the clinical impact of finding mosaicism through: embryo biopsy, chorionic villus sampling, amniocentesis, and noninvasive prenatal testing using cell-free DNA.

Low-level mosaicism for trisomy 16 at amniocentesis in a pregnancy associated with intrauterine growth restriction and a favorable outcome

OBJECTIVE

We present low-level mosaicism for trisomy 16 at amniocentesis in a pregnancy associated with intrauterine growth restriction (IUGR) and a favorable outcome.

CASE REPORT

A 31-year-old woman underwent amniocentesis at 24 weeks of gestation because of IUGR. Amniocentesis revealed a karyotype of 47,XX,+16 [3]/46,XX [22]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed gene dosage increase in chromosome 16 consistent with 28% mosaicism for trisomy 16. Uniparental disomy (UPD) 7 and UPD 11 were excluded. She underwent repeat amniocentesis at 27 weeks of gestation. Repeat amniocentesis revealed a karyotype of 47,XX,+16 [1]/46,XX [24]. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes revealed 25%-35% (log₂ ratio = 0.17-0.25) mosaicism for trisomy 16. Interphase fluorescence in situ hybridization (FISH) analysis detected trisomy 16 signals in 28/100 (28%) uncultured amniocytes. Polymorphic DNA marker analysis excluded UPD 16. Level II ultrasound revealed no fetal abnormalities except symmetric IUGR. The pregnancy was continued to 37 weeks of gestation, and a 2306-g phenotypically normal baby was delivered. The cord blood had a karyotype of 46, XX in 50/50 lymphocytes. The umbilical cord had a karyotype of 47,XX,+16 [14]/46,XX [36]. Interphase FISH analysis on buccal mucosal cells and urinary cells at age three days revealed trisomy 16 signals in 3.8% (4/106) buccal mucosal cells and 6.5% (7/107) urinary cells, compared with 1% in the normal control. Polymorphic DNA marker analysis on placenta confirmed trisomy 16 in the placenta and a maternal origin of the extra chromosome 16.

CONCLUSION

Cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes may present in mosaic trisomy 16 at amniocentesis. Low-level mosaicism for trisomy 16 at amniocentesis without maternal UPD 16 can be associated with a favorable outcome despite the presence of IUGR.

Genomic imbalances in the placenta are associated with poor fetal growth

Background

Fetal growth restriction (FGR) is associated with increased risks for complications before, during, and after birth, in addition to risk of disease through to adulthood. Although placental insufficiency, failure to supply the fetus with adequate nutrients, underlies most cases of FGR, its causes are diverse and not fully understood. One of the few diagnosable causes of placental insufficiency in ongoing pregnancies is the presence of large chromosomal imbalances such as trisomy confined to the placenta; however, the impact of smaller copy number variants (CNVs) has not yet been adequately addressed. In this study, we confirm the importance of placental aneuploidy, and assess the potential contribution of CNVs to fetal growth.

Methods

We used molecular-cytogenetic approaches to identify aneuploidy in placentas from 101 infants born small-for-gestational age (SGA), typically used as a surrogate for FGR, and from 173 non-SGA controls from uncomplicated pregnancies. We confirmed aneuploidies and assessed mosaicism by microsatellite genotyping. We then profiled CNVs using high-resolution microarrays in a subset of 53 SGA and 61 control euploid placentas, and compared the load, impact, gene enrichment and clinical relevance of CNVs between groups. Candidate CNVs were confirmed using quantitative PCR.

Results

Aneuploidy was over tenfold more frequent in SGA-associated placentas compared to controls (11.9% vs. 1.1%; p = 0.0002, OR = 11.4, 95% CI 2.5–107.4), was confined to the placenta, and typically involved autosomes, whereas only sex chromosome abnormalities were observed in controls. We found no significant difference in CNV load or number of placental-expressed or imprinted genes in CNVs between SGA and controls, however, a rare and likely clinically-relevant germline CNV was identified in 5.7% of SGA cases. These CNVs involved candidate genes INHBB, HSD11B2, CTCF, and CSMD3.

Conclusions

We conclude that placental genomic imbalances at the cytogenetic and submicroscopic level may underlie up to ~ 18% of SGA cases in our population. This work contributes to the understanding of the underlying causes of placental insufficiency and FGR, which is important for counselling and prediction of long term outcomes for affected cases.

Mosaic Trisomy 16 Associated with Left Lung Agenesis, Abnormal Left Arm, and Right Pulmonary Artery Stenosis: Expanding the Phenotype and Review of the Literature

Trisomy 16 is the most common autosomal trisomy found in spontaneous abortions with mosaic versions seen in survivors. However, surviving children have multiple congenital defects and are at risk of growth and developmental delay. We report an additional case of mosaic trisomy 16 diagnosed by amniocentesis and confirmed after birth. Our patient is the first documented case of living mosaic trisomy 16 with the malformation constellation of lung agenesis, left pulmonary artery agenesis, congenital heart defects, and ipsilateral radial ray and limb abnormalities, expanding the phenotype of this rare condition. Additionally, this individual's unique combination of lung and cardiac defects caused morbidities that were challenging to manage and complicated family counseling as well.

Vesicules or placental lakes in ultrasonography, determining the correct etiology

The prenatal examination of the placenta is often an afterthought to that of the fetus in ultrasonography. Not giving the placenta its due may however result in potentially serious placental pathologies remaining undiscovered, notably in the presence of anechoic zones. These latter have earned numerous names, including "placental lakes", "placental venous lakes", "placental lacunae" or "placental caverns" among others, but they have received little attention in the literature. We thus feel that it is essential to review the various pathologies that placental lakes may signal, since any one of them may greatly affect patient management. The difficulty resides in the diversity of these pathologies, sometimes oncological, other times fetal, and in the potential need for multidisciplinary surgery. Some of these causes of placental lakes may result in maternal or fetal complications and/or necessitate increased and casespecific surveillance. The diagnosis and treatment of such cases requires close collaboration between sonographers, obstetricians, geneticists and pathologists. The work we present here focuses on the different etiologies to consider in the presence of a lacunar placenta and the necessary diagnostic measures. Our objective is to propose a diagnostic flowchart to aid clinicians in this dense differential diagnosis.

Placental development and function in trisomy 21 and mouse models of Down syndrome: Clues for studying mechanisms underlying atypical development

Down syndrome (DS) is the most common genetic disorder leading to developmental disability. The phenotypes associated with DS are complex and vary between affected individuals. Placental abnormalities in DS include differences in cytotrophoblast fusion that affect subsequent conversion to syncytiotrophoblast, atypical oxidative stress/antioxidant balance, and increased expression of genes that are also upregulated in the brains of individuals with Alzheimer's disease. Placentas in DS are prematurely senescent, showing atypical evidence of mineralization. Fetuses with DS are especially susceptible to adverse obstetric outcomes, including early in utero demise, stillbirth and growth restriction, all of which are related to placental function. The placenta, therefore, may provide key insights towards understanding the phenotypic variability observed in individuals with DS and aid in identifying biomarkers that can be used to evaluate phenotypic severity and prenatal treatments in real time. To address these issues, many different mouse models of DS have been generated to identify the mechanisms underlying developmental changes in many organ systems. Little is known, however, regarding placental development in the currently available mouse models of DS. Based upon the relative paucity of data on placental development in preclinical mouse models of DS, we recommend that future evaluation of new and existing models routinely include histologic and functional assessments of the placenta. In this paper we summarize studies performed in the placentas of both humans and mouse models with DS, highlighting gaps in knowledge and suggesting directions for future research.

Prognosis for pregnancies with trisomy 16 confined to the placenta: A Danish cohort study

OBJECTIVE

To evaluate the risk of adverse pregnancy outcome when trisomy 16 confined to the placenta is diagnosed and to identify possible prognostic markers for adverse outcomes in these pregnancies.

METHOD

Registered cases (n = 49) of trisomy 16 diagnosed prenatally in Denmark from 1990 to 2013 were included.

RESULTS

Twenty-five of the pregnancies intended to be continued had confined placental trisomy 16 mosaicism (CPM16). Adverse pregnancy outcome was seen in 17 CPM16 pregnancies (68%), ranging from mild small for gestational age (SGA) to fetal malformations and intrauterine demise. For cases ascertained by combined first trimester screening, the median concentration of pregnancy associated plasma protein A (PAPP-A) was 0.17 MoM (IQR: 0.11 MoM). Adverse pregnancy outcome showed a trend toward an association with a high frequency of trisomic cells. Eight children (32%) were born at term with a normal birth weight and no malformations.

CONCLUSION

The risk of adverse pregnancy outcome in case of CPM16 is correlated to ascertainment by combined first trimester screening and tends to be associated with a high frequency of trisomic cells in the placenta. We recommend that variables including ascertainment, the frequency of trisomic cells, and the maternal serum concentration of PAPP-A are taken into consideration when evaluating the prognosis in CPM16 while acknowledging that these factors are strongly correlated.

Ontogenetic and Pathogenetic Views on Somatic Chromosomal Mosaicism

Intercellular karyotypic variability has been a focus of genetic research for more than 50 years. It has been repeatedly shown that chromosome heterogeneity manifesting as chromosomal mosaicism is associated with a variety of human diseases. Due to the ability of changing dynamically throughout the ontogeny, chromosomal mosaicism may mediate genome/chromosome instability and intercellular diversity in health and disease in a bottleneck fashion. However, the ubiquity of negligibly small populations of cells with abnormal karyotypes results in difficulties of the interpretation and detection, which may be nonetheless solved by post-genomic cytogenomic technologies. In the post-genomic era, it has become possible to uncover molecular and cellular pathways to genome/chromosome instability (chromosomal mosaicism or heterogeneity) using advanced whole-genome scanning technologies and bioinformatic tools. Furthermore, the opportunities to determine the effect of chromosomal abnormalities on the cellular phenotype seem to be useful for uncovering the intrinsic consequences of chromosomal mosaicism. Accordingly, a post-genomic review of chromosomal mosaicism in the ontogenetic and pathogenetic contexts appears to be required. Here, we review chromosomal mosaicism in its widest sense and discuss further directions of cyto(post)genomic research dedicated to chromosomal heterogeneity.

Do specific ultrasonography features identified at the time of early pregnancy loss predict fetal chromosomal abnormality? - A systematic review and meta-analysis

To investigate the association of specific ultrasonography features identified during the diagnosis of early pregnancy loss (EPL) and abnormal karyotype. This was a systematic review and meta-analysis conducted in accordance with PRISMA criteria. We searched PubMed, Cochrane and Ovid MEDLINE from 1977 to Jan 2017 to identify the articles that described EPL with karyotype and ultrasonography features. Risk differences were pooled to estimate the chromosomal abnormality rates in ultrasonography features, including pre-embryonic, enlarged yolk sac (YS), short crown rump length (CRL), small gestational sac (GS), symmetrical arrested growth embryo, or gestational sac with only a YS. Quality assessment of included studies was performed using Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklists for Observational Studies (2007 version). Thirteen studies were included in the meta-analysis. Chromosomal abnormality was more likely to occur in embryonic EPL and enlarged YS. On the other hand, short CRL, small GS, symmetrical arrested growth embryo, or gestational sac with only a YS, were not associated with an increased risk of fetal chromosomal abnormality. Ultrasonography features at the time of diagnosis of EPL have limited predictive value of fetal chromosomal abnormality.

Pregnancy outcome of autosomal aneuploidies other than common trisomies detected by noninvasive prenatal testing in routine clinical practice

OBJECTIVE

The objective of the study is to report the incidence and pregnancy outcome of autosomal aneuploidies other than common trisomies 21, 18, and 13 detected by noninvasive prenatal testing (NIPT) at a single center.

METHODS

Pregnant women undergoing NIPT from February 2015 to January 2018 in our center were offered expanded screening to include rare autosomal aneuploidies. Aneuploidies included extra copy chromosomes (most likely trisomies) and decreased copy chromosomes (most likely monosomies). The pregnancy outcomes of women consenting to the expanded NIPT screen were recorded.

RESULTS

Expanded NIPT was performed in 15 362 pregnancies. A total of 59 autosomal aneuploidies other than the 3 common trisomies were detected, with a positive screening rate of 0.38% (59/15 362). The screen positive rate was higher in women aged above 35 years than in those younger (0.44% vs 0.32%, P < .05). Of the screen positive results, 30.5% (18/59) were because of extra copies for chromosomes trisomy 7, 10.2% (6/59) for chromosome 22, and 8.5% (5/59) for chromosomes 8 and 16 respectively, while other choromosomes were less frequently involved. Decreased copy chromosomes were less common: 6.8% (4/59) for chromosomes 14 and 13. Mixed aneuploidies with increased copies for some chromosomes and decreased copies for others were also noted. Invasive prenatal diagnosis was performed in 61% (36/59) of the cases. Invasive test results and clinical follow-ups demonstrated that most (94.9%, 56/59) of the rare aneuploidies were false positives, probably resulting from confined placental mosaicism. Only 1 case (1.7%, 1/59) with NIPT report of extra copies of chromosome 7 and without ultrasound evidence of fetal abnormality was confirmed to be fetal mosaicism by microarray test. Uniparental disomy of whole chromosome 2 was identified by microarray analysis in 1 case with extra copy chromosome 2 detected by NIPT. Loss of heterozygocity of chromosome 7q11.23-q21.11 was detected in another case with extra copy chromosome 7. Fortunately, pregnancy outcomes of both cases were normal. Two fetal deaths attributed to severe fetal growth restriction were associated with extra copies of chromosome 16 at expanded NIPT.

CONCLUSIONS

Autosomal aneuploidies other than trisomies 21, 18, and 13 are not uncommon in routine clinical NIPT practice. Extra copies of chromosomes in rare cases can be associated with uniparental disomy. Most rare aneuploidies at NIPT have good pregnancy outcomes. Thus, invasive testing should be used with caution for these aneuploidies in routine clinical practice.

Laboratory considerations for prenatal genetic testing

New genetic tests have rapidly entered clinical care with little consistency in laboratory testing and reporting. Non-invasive prenatal screening using cell free DNA (cfDNA) may either screen for common aneuploidies alone or include chromosomal microdeletions. All cfDNA screening tests have false positives and false negatives, and accordingly laboratories should report positive and negative predictive values. In addition, since fetal fraction plays a significant role in the reliability of results, this should also be reported with all test results. Chromosomal microarray addresses significant clinically relevant information beyond that detected with standard karyotype testing but may, in less than one percent of cases, result in a variant of uncertain significance (VUS). Laboratories should indicate their policies for reporting these VUS findings. In addition, physicians using this testing should be aware of the advantages and disadvantages of the laboratory platforms. Whole-exome and whole-genome sequencing are just entering clinical care and issues of VUS, incidental findings, and phenotype/genotype correlations need to be investigated before these techniques enter routine clinical care.

Prenatally Diagnosed Rare Trisomy 16 Mosaicism in Human Amniotic Fluid Cells in the Second Trimester: A Case Report

Although trisomy 16 is commonly detected in spontaneous abortions and accounts for over 30% of cases of autosomal trisomy detected after spontaneous abortion, trisomy 16 mosaicism is rarely detected by amniocentesis in the second trimester. Here, we report a case of level III trisomy 16 mosaicism (47,XX,+16[8]/46,XX[31]) diagnosed by cytogenetic analysis of independently cultured amniotic fluid cells. The female baby was delivered at full term with low birth weight and intrauterine growth retardation, and interestingly, her karyotype was normal (46,XX). Given the difficulty in predicting the outcomes of fetuses with this mosaicism, it is recommended to inform the possibility of mosaicisms including this trisomy 16 mosaicism during prenatal genetic diagnosis and genetic counseling for parents.