Placental Mosaicism Research Articles

Comment on “Confined placental mosaicism is a diagnostic pitfall in dystrophinopathies: a clinical report”

Comment on “Confined placental mosaicism is a diagnostic pitfall in dystrophinopathies: a clinical report”

Confined Placental Mosaicism Detected With Non-Invasive Prenatal Testing: Is There an Association Between Mosaic Ratio and Pregnancy Outcome?

Confined placental mosaicism (CPM) is associated with an increased risk for pregnancy complications, such as fetal growth restriction (FGR), preterm birth and hypertensive disorders. Pregnancies with possible CPM can be identified with non-invasive prenatal testing (NIPT). We performed a retrospective cohort study to investigate whether the mosaic ratio, as calculated with the Veriseq v2 used for NIPT, can predict adverse pregnancy outcomes in cases of CPM. A mosaic ratio for trisomies detected by NIPT and obstetric data such as fetal growth, structural fetal anomalies and birthweight were retrospectively studied in a cohort of patients with CPM diagnosed between February 2021 and October 2023. Structural and sex chromosomal aberrations were not included in this study. Of 122 CPM cases, 52 cases (42.6%) showed adverse perinatal outcomes, including FGR, low birthweight, hypertensive disorders, or preterm birth. A significantly higher mosaic ratio was found in the adverse outcome group compared to those with normal outcome, but a clear-cut threshold could not be set, except potentially for trisomy 16. There is an association between the mosaic ratio and adverse pregnancy outcomes in cases of CPM. However, without a clear-cut threshold, it cannot be used for the individual patient for differentiation between CPM with and without clinical consequences.

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

BackgroundMosaicism, 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. ObjectiveTo 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 DesignA 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. ResultsOf 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]). ConclusionIntroducing 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.

Monocentric Study on the Performance of Noninvasive Prenatal Testing on Cell-Free DNA for the Detection of Monosomy X.

Increasing the PPV of monosomy X detected by the non-invasive prenatal test (NIPT) by discriminating a (mosaic) monosomy X genotype of fetal versus maternal origin. Out of 30,700 women referred for NIPT between January 2014 and December 2021, 79 had a high risk result for 45,X. Discrimination between fetal and maternal 45,X was made based on the values for ffX, ffY and SeqFF. Follow-up was provided through analysis of amniotic fluid, maternal blood, umbilical cord blood, neonatal blood and/or placental biopsies. Follow-up data were available for 70/79 women; after exclusion of one twin pregnancy, 69 pregnancies were evaluated (87.3%). Forty one of those were correctly predicted as being maternal or fetal, for an overall PPV of 59.4% (95% confidence interval [CI] 47%-71%). Of the 33 predicted fetal cases with follow-up, 11 were indeed of fetal origin, equating to a PPV of 33.3% (95% CI 18%-52%); three additional cases turned out to be placental in origin, six were maternal and for 13, no explanation could be found. The PPV of maternal cases was 88.2% (30/34 cases with follow-up correctly predicted; 95% CI 73%-97%). One case turned out to be fetal; for the other three, follow-up studies failed to prove the presence of monosomy X. Two cases for which no prediction on the origin of the monosomy X could be made (inconclusive high-risk NIPT result) turned out to have confined placental mosaicism. Although the PPV for fetal monosomy X remains lower than for the common trisomies, the total PPV for 45,X screening with NIPT can be improved by discerning fetal from (mosaic) maternal 45,X genotype. Thorough follow-up to determine the origin of the aberrant NIPT result is advised, so that women can be adequately counseled on the risk in their current and future pregnancies and, in case of maternal mosaic monosomy X, of their own prospects.

Confined placental mosaicism is a diagnostic pitfall in dystrophinopathies: a clinical report.

Single-gene copy number variants (CNVs) limited to placenta although rarely identified may have clinical implications. We describe a pregnant woman referred for chorionic villus sampling due to increased fetal nuchal translucency. Incident intragenic deletion of Duchenne muscular dystrophy (DMD) gene, affecting exons 56 and 57, was identified in a male fetus in ~23-30% of placental cells by chromosomal microarray and confirmed using multiplex ligation-dependent probe amplification (MLPA). Rapid aneuploidy testing showed normal results and the deletion was not detected in the mother. Subsequent analyses on amniotic cells yielded a normal DMD gene result, corroborating the confined placental nature of the mosaicism. Hence, this report emphasizes the importance of conducting amniocentesis following detection of mosaicism for single gene CNVs on chorionic villi, in order to preclude confined placental mosaicism (CPM). As far as we know, this report marks only the second documented situation of CPM involving an intragenic DMD deletion.

Clinicopathological and molecular genetic features of confined placental mosaicism

Objective: To investigate the clinicopathological and genetic features of confined placental mosaicism (CPM) and its effect on fetal intrauterine growth. Methods: Fourteen CPM cases of Haidian Maternal and Children Health Hospital were collected from May 2018 to March 2022. Clinicopathological examination on placental specimens and molecular genetic analysis were performed. Results: The age of the parturient women ranged from 27 to 34 years, with an average age of (30.0±3.54) years. The gestational weeks ranged from 35+1 to 41+2 weeks. There were 4 premature births and 10 term births, among which 6 were female and 8 were male fetuses. Nine cases (9/14) had adverse pregnancy outcomes, including 7 cases of fetal growth restriction. The weight of CPM placenta decreased, with 6 cases below the 10th percentile of weight standards and 5 cases between the 10th and 25th percentile. All 14 CPM placental specimens showed morphological changes of perfusion dysfunction to varying degrees, with mainly placental-maternal vascular malperfusion followed by placental-fetal vascular malperfusion. The mosaic chromosomes in different CPM cases varied, with 16-trisomy/monosomy mosaicism being the most common followed by 7-trisomy and 21-trisomy/monosomy mosaicism. The mosaic proportion was unequal in different parts of the same CPM placenta, with the mosaic proportion of umbilical cord, fetal membranes, fetal surface, maternal surface, and edge ranging from 1% to 70%. Conclusions: The mosaic chromosomes in different CPM cases vary, and the mosaic proportion is unequal in different parts of the same CPM placenta. The pathological morphology is mainly manifested as perfusion dysfunction, which can lead to adverse pregnancy outcomes such as fetal growth restriction and preterm birth.

P-439 Analysis of Products of Conception (POC) using Whole Genome Next Generation Sequencing (NGS) in pregnancy loss after euploid or mosaic embryo transfer

Abstract Study question What is the outcome of genetic assessment for fetal chromosomal aberrations in miscarriages after euploid/mosaic embryo transfers (ET)? Summary answer POC testing should be recommended in patients with E/M-ET to screen for chromosomal aberrations occurring post-implantation or beyond the detection limit of PGT-A testing What is known already Spontaneous abortion is the most common complication of pregnancy, affecting approximately 15% of clinically recognized pregnancies. Although the etiology is diverse, fetal chromosomal aberrations account for 50-70% of first trimester miscarriages. Assessment of the fetal chromosomal composition is recommended by ACOG guidelines and aids in counselling and management of patients’ reproductive options. The value of this assessment in patients with miscarriage after euploid/mosaic ET has not evaluated. At the same time there is generally a lack of follow-up studies to examine the accuracy of PGT-A testing and investigate the rates of post-implantation errors causing miscarriage. Study design, size, duration This retrospective study had REB approval. This study was performed at the CReATe Fertility Centre and its Reproductive Genetics Laboratory in Toronto, Canada, between January 2019-December 2023.We evaluated the molecular karyotype of POC samples from first trimester &amp;lt;12GW miscarriages after ART: IVF-PGT-group euploid (E) and mosaic (M) embryo transfers (ET) and IVF-group; IUI and natural conception-NC groups; while controlling for maternal cell contamination (MCC) by high-resolution whole genome NGS. Participants/materials, setting, methods 549 POC samples from early miscarriages after fertility treatment were obtained by suction-dilatation-and curettage. Selection of fetal tissue/chorionic villi (4 representative samples for each case) was performed under a dissecting microscope. Maternal and paternal DNA was obtained to test for MCC. MCC was determined by testing maternal/gestational carrier and fetal DNA (fDNA) with highly informative STRs (AmpFLSTR Identifiler kit). Whole genome low-pass NGS (0.1xcoverage) was performed using the Illumina platform and analyzed with NxClinical Software. Main results and the role of chance Fetal tissue was obtained from 90.7% (498/549) of tested samples and the rest had MCC (9.3%, 51/549): IVF-PGT-A(n = 183), IVF(n = 92), IUI(n = 46) and NC(n = 173). The overall mean maternal age was 37±3.2years. The average gestational age at D&amp;C was 8w4d (range 5w-12w6d). Overall, NGS analysis of fDNA showed 44.6% male and 55.3% female fetuses, 57.6% (287/498) were euploid, 39.5% (197/498) were aneuploid and 1.8% (9/498) were mosaic. In IVF-PGT-A group there were 169 POC from euploid ET and 14 from mosaic ET. 98.2% (n = 166/169) of POCs from IVF-PGT-A euploid-ETs were confirmed as euploid, and 3 had confined placental mosaicism (CPM) (trisomy-11, trisomy-4, monosomy-X). POC from mosaic-ET (n = 14), showed CPM in 3/14(21.4%): TE mosaicism was confirmed in 1/14(7.1%), 2/14(14.3%) had CPM differing from the PGT-A result, 11/14(78.6%) were euploid. POC euploidy rate in IVF (no PGT-A) group was 59.8%(55/92), in IUI 34.8%(16/46) and in NC 24.3%(42/173). In NC group CPM was detected in 1.7%(3/173). The frequency of aberrations detected in POC(n = 197) were: T22, 16.5%; T16,12.9%; T15, 11.3%; T20, 5.2%; T8, 3.6%; T7, T9 and T13, 3.1%; T10 and T14, 2.6%; T18 and T21, 2.1%; T12, 1.5%; 1% of each T2, T4 and T11; monosomy-X,6.7% and 11.3% triploid (69,XXY or 69,XXX). Limitations, reasons for caution MCC is relatively high in POC samples from early pregnancies (9.3%) and controlling for it is warranted. Although 4 representative samples of placental tissue were tested, the true extent and existence of CPM may not be captured correctly. Wider implications of the findings NGS analysis of POC from first trimester miscarriages after fertility treatment would improve diagnostic accuracy, and could aid in patient counselling and management. We observed high PGT-A accuracy (100% for gender) and 98.2% for fetal ploidy with CPM rate of 1.8% (which is lower than observed after CVS (4%)). Trial registration number not applicable

Trophectoderm biopsy is associated with lower risks of moderate to extreme prematurity and low birthweights: a national registry cohort study of singleton livebirths from frozen-thawed blastocyst transfers

BackgroundTrophectoderm biopsy has become the mainstay assisted reproductive technique performed for preimplantation genetic testing, accounting for 43.8% of embryo transfer cycles in the US in 2019 alone. Despite its prevalence, data on the obstetric and perinatal outcomes post trophectoderm biopsy remains sparse and mixed. ObjectiveThis study aimed to examine the risks of adverse perinatal outcomes in birth weights and prematurity after transfers of vitrified-thawed blastocyst with trophectoderm biopsy for preimplantation genetic testing. Study DesignThis was a retrospective observational cohort study of 45,712 singleton live births resulting from autologous vitrified-thawed blastocyst transfer cycles with or without trophectoderm biopsy for preimplantation genetic testing, reported by participating member clinics to the Society for Assisted Reproductive Technology national registry between 2014 and 2017. Adverse perinatal outcomes of preterm births and low birth weights were analyzed. Multivariable regression analyses were performed to control for covariates. Comparing the trophectoderm biopsy (n=21,584) and no trophectoderm biopsy (n=24,128) groups, adjusted odds ratios were calculated for the outcomes of small for gestational age, large for gestational age, low birth weight < 2,500 g, very low birth weight < 1,500 g, extremely low birth weight < 1,000 g, late preterm births < 37 weeks, moderate preterm births < 34 weeks, and extremely preterm births < 28 weeks. ResultsWomen in the trophectoderm biopsy group were older and more likely to have prior pregnancies, deliveries, and history of spontaneous abortions. Tobacco use, diminished ovarian reserve, and recurrent pregnancy loss were also more prevalent in the trophectoderm biopsy group. Trophectoderm biopsy was not associated with small-for-gestational-age (aOR 0.97, 95% CI 0.85-1.12, p-value 0.72) or large-for-gestational-age newborns (aOR 1.10, 95% CI 0.99-1.22, p-value 0.09). Risks of preterm births < 37 weeks gestation were similar between the biopsy and non-biopsy groups (aOR 0.93, 95% CI 0.85-1.02, p-value 0.11). Trophectoderm biopsy was associated with a significantly lower risk of low birthweight < 2,500 g (aOR 0.80, 95% CI 0.70-0.92, p-value <0.001), very low birthweight < 1,500 g (aOR 0.62, 95% CI 0.46-0.83, p-value <0.001), extremely low birthweight < 1,000 g (aOR 0.48, 95% CI 0.31-0.74, p-value <0.001), moderate preterm birth < 34 weeks (aOR 0.76, 95% CI 0.64-0.91, p-value 0.003), and extreme preterm birth < 28 weeks (aOR 0.63, 95% CI 0.43-0.92, p-value 0.017). ConclusionTrophectoderm biopsy is not associated with increased risks of small for gestational age, large for gestational age, or late preterm birth. Risks of low birthweight, very low birthweight, and extremely low birthweight from moderate and extreme preterm births are lower after trophectoderm biopsy, possibly by selecting against confined placental mosaicism or inducing placental epigenetic changes, the mechanisms of which warrant further investigation.

Confined placental mosaicism: Distribution of chromosomally abnormal cells over the term placenta

ObjectiveNon-invasive prenatal testing (NIPT) investigates placental DNA and may detect confined placental mosaicism (CPM). The aim of this study was to confirm CPM in the term placenta in cases with abnormal NIPT but normal follow-up cytogenetic studies of fetus and mother. Additionally we examined the distribution of abnormal cells over the placenta. MethodsFour chorionic villus (CV) biopsies from four placental quadrants were requested in cases where CPM was assumed. Both cell lineages of the CV, cytotrophoblast (CTB) and mesenchymal core (MC), were analyzed separately with SNP array. ResultsThe chromosome aberration was confirmed in 67 % of the placentas. Three quarters of the CTB and MC biopsies from these mosaic placentas were uniformly normal (57 %) or abnormal (20 %), and a minority showed mosaicism. Among 16 cases of CPM where first trimester CV were examined as well, 11 had chromosomally normal results during pregnancy. DiscussionCytogenetic investigations of term placental biopsies suspected to be affected with CPM did not reveal the chromosome aberration in one third of the placentas. This is caused by the patchy pattern in which chromosomally abnormal cells are distributed over the placenta with the majority of the biopsies being uniformly normal. Further CPM research, including its clinical impact, requires the analysis of more than four biopsies to get insight into the extent of the affected part. Moreover, a subset of CPM type 1 and 3 seems to be only detectable with NIPT and not with first trimester CVS.

Direct embryonic biopsy with transcervical embryoscopy is an effective method for karyotyping and morphology assessment in miscarriages

PurposeThe main purpose of this study is to compare the validity of transcervical embryoscopy method with standard uterine evacuation method in detecting more accurate karyotypes in miscarriages below tenth week of pregnancy. Additionally, the frequency and distribution of fetal morphological abnormality were evaluated.MethodsA prospective study was carried out at the Gazi University Faculty of Medicine, Department of Obstetrics and Gynecology. Patients with missed abortions between sixth and tenth gestational weeks were included in the study group, and fetal morphological examination and direct embryonic biopsy were performed by transcervical embryoscopy. The control group consisted of patients who experienced miscarriage and genetic material obtained from routine uterine evacuation between February and October 2023.ResultA total of 60 patients in the study group and 189 patients in the control group were evaluated. The median ages, previous miscarriage numbers, median gravida numbers, and median gestational weeks were comparable between groups. Chromosomal abnormality was detected in 24 (42.8%) and 52 embryos (29.9%) in the study and control groups, respectively (p = 0.004). Culture failure rates were 6.6% (n = 4) and 7.9% (n = 15) in the study and control groups, respectively. In the study group, 12 embryos had a morphological abnormality in which 6 of them had normal karyotype.ConclusionDirect embryonic biopsy with transcervical embryoscopy is an effective method to exclude maternal decidual cell contamination and placental mosaicism in miscarriages for karyotype analysis. In addition, detecting anomalies in morphology might contribute our understanding in the process of miscarriages which arises independent from structural/numerical chromosomal abnormalities.

The impact of confined placental mosaicism on prenatal cell-free DNA screening: Insights from a monocentric study of 99 cases

IntroductionConfined placental mosaicism (CPM) is thought to be one of the main sources of false-positive prenatal cell-free DNA (cfDNA) screening results, but extensive and systematic studies to prove this statement are limited. We evaluate the contribution of CPM to false-positive prenatal cfDNA screening results in the largest cohort published to date. MethodWe systematically offered postnatal analysis on placenta and umbilical cord to women who had a negative amniocentesis following a positive prenatal cfDNA screening result. A standardized protocol was used in which (when available) biopsies were taken at five locations in the placenta and umbilical cord. ResultsWe analyzed a series of 99 placentas. CPM could be confirmed in 32.3 % of cases (32/99). CPM was detected across all subtypes of chromosomal aberrations (common and rare autosomal trisomies, sex chromosome abnormalities, copy number variations and autosomal monosomies). A lower detection rate was present in umbilical cord biopsies in comparison with placental biopsies. When comparing different sections of the placenta, no clear difference could be observed with regard to the probability of CPM being present nor to the grade of mosaicism. DiscussionWe confirm an important role for CPM in explaining false-positive prenatal cfDNA screening results. Placental regional differences are common. Given its limited clinical relevance, we do however not advocate placental studies in a diagnostic setting.

Clinical outcomes of screen-positive genome-wide cfDNA cases for trisomy 20: results from the global expanded NIPT Consortium.

Trisomy 20 has been shown to be one of the most frequent rare autosomal trisomies in patients that undergo genome-wide noninvasive prenatal testing. Here, we describe the clinical outcomes of cases that screened positive for trisomy 20 following prenatal genome-wide cell-free (cf.) DNA screening. These cases are part of a larger cohort of previously published cases. Members of the Global Expanded NIPT Consortium were invited to submit details on their cases with a single rare autosomal aneuploidy following genome-wide cfDNA screening for retrospective analysis. Clinical details including patient demographics, test indications, diagnostic testing, and obstetric pregnancy outcomes were collected. Genome-wide cfDNA screening was conducted following site-specific laboratory procedures. Cases which screened positive for trisomy 20 (n = 10) were reviewed. Clinical outcome information was available for 90% (9/10) of our screen-positive trisomy 20 cases; the case without diagnostic testing ended in a fetal demise. Of the nine cases with outcome information, one was found to have a mosaic partial duplication (duplication at 20p13), rather than a full trisomy 20. Only one case in the study cohort had placental testing; therefore, confined placental mosaicism could not be ruled out in most cases. Adverse pregnancy outcomes were seen in half of the cases, which could suggest the presence of underlying confined placental mosaicism or mosaic/full fetal trisomy 20. Based on our limited series, the likelihood of true fetal aneuploidy is low but pregnancies may be at increased risk for adverse obstetric outcomes and may benefit from additional surveillance.

Genetic origin analysis of regions of homozygosity in three cases

To explore the genetic characteristics of three fetuses with regions of homozygosity (ROH). Three fetuses with ROH diagnosed at Nanjing Drum Tower Hospital on December 2, 2020, March 19, 2021, and May 27, 2022, respectively were selected as the study subjects. Clinical data of the fetuses were collected. Chromosomal microarray analysis (CMA) was used to detect the ROH, and tandem repeat sequences (STR)-based multiplex PCR assay was used to identify the mosaicism status in fetus 1. Partial maternal isodisomy (iUPD) (16) was found in fetus 1, for which trisomy rescue may be accountable. Meanwhile, the fetus also has confined placental mosaicism (CPM) but not true mosaicism. The formation mechanism of ROH for fetus 2 was identity by descent. Partial maternal iUPD (7) was found in fetus 3, which may be due to gametic recombination. The ROH of the three fetuses were inherited from both parents or the mother. Above findings suggested that it is justified to detect ROH on imprinting disorder-related chromosomes when potential uniparental disomy is suspected.

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

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

Noninvasive single-cell-based prenatal genetic testing: Aproof of concept clinical study.

To clinically assess a cell-based noninvasive prenatal genetic test using sequence-based copy number analysis of single trophoblasts from maternal blood. Blood was obtained from 401 (243+158) individuals (8-22weeks) and shipped overnight. Red cells were lysed, and nucleated cells stained for cytokeratin (CK) and CD45 and enriched for positive CK staining. Automated scanning was used to identify and pick single CK+ /CD45- trophoblasts which were subjected to next-generation sequencing. Blood was obtained from 243 pregnancies scheduled for CVS or amniocentesis. Luna results were normal for 160 singletons while 15 cases were abnormal (14 aneuploidy and one monozygotic twin with Williams syndrome deletion). The deletion was confirmed in both fetuses. Placental mosaicism occurred in 7 of 236 (3.0%) Luna cases and in 3 of 188 (1.6%) CVS cases (total 4.6%). No scorable trophoblasts were recovered in 32 of 236 usable samples. Additionally, 158 low-risk pregnancies not undergoing CVS/amniocentesis showed normal results in 133 cases. Seven had aneuploidy results, and there were three likely pathogenic deletions/duplications, including one15q11-q13 deletion. Although the sample size is modest and statistically accurate measures of test performance are not possible, the Luna test detected aneuploidy and deletions/duplications based on concordance with CVS/amniocentesis.

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

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. Cohort study using routinely collected perinatal data and cytogenetic data of non-invasive prenatal testing, the first trimester chorionic villi sampling and postnatal placentas. 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. 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.

Genetic analysis of the false positive trisomy 7 and false negative trisomy 18 by NIPT-PLUS

To explore the cause of inconsistency between the results of trisomy 7 by expanded non-invasive prenatal testing (NIPT-PLUS) and trisomy 18 by prenatal diagnosis. A pregnant woman who received genetic counseling at Jiaozuo Maternal and Child Health Care Hospital on July 5, 2020 was selected as the study subject. NIPT-PLUS, systematic ultrasound and interventional prenatal testing were carried out. The middle segment and root of umbilical cord, center and edge of the maternal and fatal surface of the placenta were sampled for the validation by copy number variation sequencing (CNV-seq). The result of NIPT-PLUS indicated that the fetus has trisomy 7. Systematic ultrasound has shown multiple malformations including atrioventricular septal defect, horseshoe kidney, and rocker-bottom feet. However, QF-PCR, chromosomal karyotyping analysis, and CNV-seq of amniotic fluid samples all showed that the fetus was trisomy 18. Validation using multiple placental samples confirmed that the middle segment of the umbilical cord contains trisomy 18, the center of the placenta contained trisomy 7, and other placental sites were mosaicism for trisomy 7 and trisomy 18. Notably, the ratio of trisomy 18 became lower further away from the umbilical cord. The false positive results of trisomy 7 and false negative trisomy 18 by NIPT-PLUS was probably due to the existence of placental mosaicism. Strict prenatal diagnosis is required needed aneuploidy is detected by NIPT-PLUS to exclude the influence of placental mosaicisms.

Contribution of uniparental disomy to fetal growth restriction: a whole-exome sequencing series in a prenatal setting

Fetal growth restriction (FGR), a leading cause of perinatal morbidity and mortality, is caused by fetal, maternal, and placental factors. Uniparental disomy (UPD) is a rare condition that leads to imprinting effects, low-level mosaic aneuploidies and homozygosity for pathogenic variants. In the present study, UPD events were detected in 5 women with FGR by trio exome sequencing (trio-WES) of a cohort of 150 FGR cases. Furthermore, noninvasive prenatal testing results of the 5 patients revealed a high risk of rare autosomal trisomy. Trio-WES showed no copy-number variations (CNVs) or nondisease-causing mutations associated with FGR. Among the 5 women with FGR, two showed gene imprinting, and two exhibited confined placental mosaicism (CPM) by copy number variant sequencing (CNV-seq). The present study showed that in FGR patients with UPD, the detection of imprinted genes and CPM could enhance the genetic diagnosis of FGR.

Maternal Uniparental Isodisomy of Chromosome 2 Leading to Homozygous Variants in SPR and ZNF142 : A Case Report and Review of the UPD2 Literature.

We report a 4-year-old girl with neurodevelopmental abnormalities who has maternal uniparental isodisomy of chromosome 2 leading to homozygosity for a likely pathogenic variant in SPR , and a variant of uncertain significance in ZNF142 . Biallelic pathogenic variants in SPR lead to sepiapterin reductase deficiency (SRD), a dopa-responsive dystonia. Pathogenic variants in ZNF142 are associated with an autosomal recessive neurodevelopmental disorder characterized by impaired speech and hyperkinetic movements, which has significant clinical overlap with SRD. Our patient showed dramatic improvement in motor skills after treatment with levodopa. We also reviewed 67 published reports of uniparental disomy of chromosome 2 (UPD2) associated with various clinical outcomes. These include autosomal recessive disorders associated with loci on chromosome 2, infants with UPD2 whose gestations were associated with confined placental mosaicism for trisomy 2 leading to intrauterine growth restriction with good postnatal catchup growth, and normal phenotypes in children and adults with an incidental finding of either maternal or paternal UPD2. These latter reports provide support for the conclusion that genes located on chromosome 2 are not subject to imprinting. We also explore the mechanisms giving rise to UPD2.

Результати комплексних пренатальних обстежень за наявності дисбалансу хромосоми 21 у плода

Purpose - to characterize the cases of chromosome 21 imbalance in fetuses of high-risk pregnant women, to describe prenatal cytogenetic diagnosis and associated ultrasound findings - structural anomalies and soft markers. Materials and methods. The results of complex prenatal examination of high-risk pregnant women in the Department of Fetal Medicine of the SI “Institute of Pediatrics, Obstetrics and Gynecology named after academician O.M. Lukyanova of the NAMS of Ukraine” during 5 years period were analyzed: results of ultrasound and cytogenetic exams of 200 cases of chromosome 21 imbalance in the fetus. Results. Among 4,748 prenatal cytogenetic testing of fetuses of high-risk women abnormal karyotypes with an imbalance of chromosome 21 were found in 200 (4.21%) cases. In the majority of cases Down's syndrome (DS) was diagnosed (n=199; 99.5%), in 1 (0.2%) case - deletion of chromosome 21. In DS, regular trisomy of chromosome 21 was found in 191 (95.97%) cases, translocant forms - in 5 (2.51%) cases, in 1 (0.5%) case there was there was an additional sex chromosome, and in 1 (0.5%) - a variant with two cell lines. In 1 (0.5%) case limited placental mosaicism was present, with a false negative result that required verification by the analysis of fetal lymphocytes obtained during cordocentesis. Advanced maternal age (≥35 years) was registered in less than half of fetal DS cases (n=92/199, 46.2%). The main indications for invasive procedures and their types are described. It was demonstrated that ultrasound findings (structural anomalies and/or “soft” markers for chromosomal pathology) were present in 78% of fetal chromosome 21 imbalance; nevertheless in 22% ultrasound findings were absent, and the indication for invasive procedures were advanced maternal age or isolated changes of biochemical markers. Conclusions. Chromosome 21 imbalance in fetuses is mainly represented by trisomy, cases of chromosome 21 deletion are extremely rare. Targeted ultrasound examination is important for screening and diagnosis of fetal chromosomal abnormalities. High-risk pregnant women shouldn’t be reassured in case of “normal” ultrasound exam results. Under certain conditions, it is advisable to perform placental biopsy in the II trimester of pregnancy, but only in specialized tertiary centers or departments. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the patient was obtained for conducting the studies. No conflict of interests was declared by the authors.