Cell-free DNA screening for common autosomal trisomies using rolling-circle replication in twin pregnancies.

OBJECTIVE: To evaluate the performance of prenatal screening for common autosomal trisomies in twin pregnancies through the use of rolling-circle replication (RCR)-cfDNA as a first-tier test. METHOD: Prospective multicenter study. Women who underwent prenatal screening for trisomy (T) 21, 18 and 13 between January 2019 and March 2022 in twin pregnancies were included. Patients were included in two centers. The primary endpoint was the rate of no-call results in women who received prenatal screening for common autosomal trisomies by RCR-cfDNA at the first attempt, compared to that in prospectively collected samples from 16,382 singleton pregnancies. The secondary endpoints were the performance indices of the RCR-cfDNA. RESULTS: 862 twin pregnancies underwent screening for T21, T18 and T13 by RCR-cfDNA testing at 10-33 weeks' gestation. The RCR-cfDNA tests provided a no-call result from the first sample obtained from the patients in 107 (0.7%) singleton and 17 (2.0%) twin pregnancies. Multivariable regression analysis demonstrated that significant independent predictors of test failure were twin pregnancy and in vitro fertilization conception. All cases of T21 (n = 20/862; 2.3%), T18 (n = 4/862; 0.5%) and T13 (n = 1/862; 0.1%) were correctly detected by RCR-cfDNA (respectively, 20, 4 and 1 cases). Sensitivity was 100% (95% CI, 83.1%-100%), 100% (95% CI 39.8%-100%) and 100% (95% CI 2.5%-100%) for T21, T18 and T13, respectively, in twin pregnancies. CONCLUSION: The RCR-cfDNA test appears to have good accuracy with a low rate of no-call results in a cohort of twin pregnancies for the detection of the most frequent autosomal trisomies.

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.

Numbers of prenatal cell-free DNA screens performed: Results of a 2022 CAP exercise.

OBJECTIVE: Determine current analytical methods and number of cell-free (cf) DNA prenatal screening tests performed for common trisomies. METHODS: The College of American Pathologists 2022-B Noninvasive Prenatal Testing exercise was distributed in December 2022 to 93 participants in 22 countries. Supplemental questions included the number of tests performed in a recent month and the proportion of samples originating outside the United States (US). RESULTS: Eighty-three participants from three continents returned results; 74 (89%) were suitable for the analyses. Nine manufacturer/platform combinations were identified, most commonly Illumina/Nextseq (55%). The most common methodology was whole genome sequencing (76%). Annualized cfDNA tests were 2.80 million, with Asian, European and North American participants representing 10.6%, 6.5% and 82.9% of tests, respectively. When restricted to US in-country tests, the annualized rate was 2.18 million, with four of 20 participants testing 79.2%. Among 73 respondents, 63 (86%) were for-profit, eight (11%) were non-profit academic or government supported and the remaining two included hospital-based and private non-profit. Eighteen (25%) supported relevant academic training. CONCLUSION: In 2011, screening for common trisomies was based on serum/ultrasound markers with an estimated 2.96 million US pregnancies screened in 131 laboratories. In 2022, cfDNA-based screening was offered by 20 laboratories testing 2.18 million US pregnancies.

Performance of cell-free DNA testing for common fetal trisomies in triplet pregnancies.

OBJECTIVE: In singleton pregnancies, the use of cell-free DNA (cfDNA) analysis as a screening test for common fetal trisomies has spread worldwide though we still lack sufficient data for its use in triplet pregnancies. The objective of this study is to assess the performance of cfDNA testing in detecting fetal aneuploidies in triplet pregnancies as a first-tier test. METHOD: We performed a retrospective cohort study including data from pregnant women with a triplet pregnancy who underwent cfDNA testing between May 1, 2017, and January 15, 2020. cfDNA was obtained by massive parallel sequencing (VeriSeq NIPT solution; Illumina®). The objectives of the study were to assess the diagnostic performance of cfDNA testing for trisomy 21 (T21) (primary outcome), trisomy 18 (T18) and 13 (secondary outcomes). RESULTS: During the study period, cfDNA testing was performed in 255 women with triplet pregnancy, of which 165 (64.7%) had a neonatal outcome available. Three tests were positive for T21, one of which was confirmed by an antenatal karyotype, and the other was confirmed at birth. The third case did not undergo an invasive procedure and was not confirmed at birth (false positive). In one case, cfDNA testing was positive for T18 and was confirmed by an antenatal karyotype. There were no cases of trisomy 13 in the cohort. The no-call rate was 2.4% at first sampling. Fifty-eight (22.7%) women had embryo reduction, which in 40 (69%) of whom was performed after the cfDNA test result. CONCLUSION: cfDNA testing could be offered as primary screening for main fetal aneuploidies in triplet pregnancies after provision of appropriate patient information.

Correlation between telomere shortening in maternal peripheral blood and fetal aneuploidy.

BACKGROUND: This study aimed to assess whether maternal telomere length is a more accurate predictor of trisomy 21 than maternal age while also exploring the factors influencing maternal and fetal telomere length. METHODS: Forty mothers with fetuses carrying extra maternal copies of chromosome 21 were defined as trisomy 21 cases, and 18 mothers with normal karyotype fetuses were defined as controls. Telomere lengths of maternal blood lymphocytes and amniotic fluid cells were determined using real-time polymerase chain reaction. Fetal and maternal telomere lengths were compared between the two groups. Moreover, we analyzed the factors influencing maternal and fetal telomere length in the trisomy 21 pedigree. A logistic regression model was used to analyze the correlation between maternal telomere length and trisomy 21 risk. In addition, receiver operating characteristic (ROC) curve analysis was used to determine the accuracy of using maternal telomere length as an indicator of trisomy 21 risk. RESULTS: The study revealed that both maternal and fetal telomere lengths were significantly shorter in trisomy 21 cases than in the controls. In the trisomy 21 group, the maternal age, occupation, and nationality showed no significant correlation with their telomere length; fetal telomere length exhibited a positive correlation with maternal telomere length. Furthermore, maternal telomere length shortening is associated with trisomy 21 (OR = 0.311; 95% CI, 0.109-0.885, P < 0.05). The results of ROC curve analysis indicated that a combined assessment of maternal age and maternal telomere length predicted fetal chromosome trisomy more effectively than a single assessment (area under the curve 0.808, 95% CI, 0.674-0.941, P < 0.001). CONCLUSION: Maternal age combined with maternal telomere length proved to be a superior predictor of trisomy risk. Additionally, maternal telomere length was found to influence fetal telomere length.

Prenatal diagnosis of a trisomy 7 mosaic case: CMA, CNV-seq, karyotyping, interphase FISH, and MS-MLPA, which technique to choose?

OBJECTIVE: This study aims to perform a prenatal genetic diagnosis of a high-risk fetus with trisomy 7 identified by noninvasive prenatal testing (NIPT) and to evaluate the efficacy of different genetic testing techniques for prenatal diagnosis of trisomy mosaicism. METHODS: For prenatal diagnosis of a pregnant woman with a high risk of trisomy 7 suggested by NIPT, karyotyping and chromosomal microarray analysis (CMA) were performed on an amniotic fluid sample. Low-depth whole-genome copy number variation sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were used to clarify the results further. In addition, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) was performed to analyze the possibility of uniparental disomy(UPD). RESULTS: Amniotic fluid karyotype analysis revealed a 46, XX result. Approximately 20% mosaic trisomy 7 was detected according to the CMA result. About 16% and 4% of mosaicism was detected by CNV-seq and FISH, respectively. MS-MLPA showed no methylation abnormalities. The fetal ultrasound did not show any detectable abnormalities except for mild intrauterine growth retardation seen at 39 weeks of gestation. After receiving genetic counseling, the expectant mother decided to continue the pregnancy, and follow-up within three months of delivery was normal. CONCLUSION: In high-risk NIPT diagnosis, a combination of cytogenetic and molecular genetic techniques proves fruitful in detecting low-level mosaicism. Furthermore, the exclusion of UPD on chromosome 7 remains crucial when NIPT indicates a positive prenatal diagnosis of trisomy 7.

Prenatal diagnosis of 18p deletion and 8p trisomy syndrome: literature review and report of a novel case.

18p deletion syndrome constitutes one of the most frequent autosomal terminal deletion syndromes, affecting one in 50,000 live births. The syndrome has un-specific clinical features which vary significantly between patients and may overlap with other genetic conditions. Its prenatal description is extremely rare as the fetal phenotype is often not present during pregnancy. Trisomy 8p Syndrome is characterized by heterogenous phenotype, with the most frequent components to be cardiac malformation, developmental and intellectual delay. Its prenatal diagnosis is very rare due to the unspecific sonographic features of the affected fetuses. We present a very rare case of a fetus with multiple anomalies diagnosed during the second trimester whose genomic analysis revealed a 18p Deletion and 8p trisomy Syndrome. This is the first case where this combination of DNA mutations has been described prenatally and the second case in general. The presentation of this case, as well as the detailed review of all described cases, aim to expand the existing knowledge regarding this rare condition facilitating its diagnosis in the future.

Maternal input to 24-month-old children with sex chromosome trisomies.

BACKGROUND: Maternal input plays an important role in influencing linguistic development during the first years of life, and it is evident that mothers adapt their language according to their child's characteristics. Recently, it was demonstrated that maternal input addressed to children with sex chromosome trisomies (SCTs) at 8 months of age is prosodically and functionally different from that addressed to typically developing (TD) peers. AIMS: The study aimed at analysing maternal input at 24 months when the presence of a language delay could be more evident than during the preverbal stage. We were interested in examining if maternal input was influenced by a diagnosis of SCT (by comparing children with SCT and TD children) or by children's linguistic level (by comparing children with weak lexical ability versus children with typical lexical ability regardless of the presence of genetic diagnosis). METHODS AND PROCEDURES: Forty-four mother-child dyads in which the children had an SCT and 20 mother-child dyads in which the children were TD participated in the study. Of these 64 dyads, 23 children (21 with SCTs and two TD children) formed the group of children with weak lexical ability (children with a vocabulary size lower than 50 words at 24 months). Maternal utterances were collected during one video-recorded play session and were then coded considering both the linguistic and functional features of the input. OUTCOMES AND RESULTS: The results showed that the input addressed to 24-month-old children with SCTs is as rich and complex as that addressed to TD peers. Moreover, no significant differences in the functions expressed by maternal input were found (all ps > 0.05). Comparing the children with weak lexical ability and the children with typical lexical ability in our sample, having a poor vocabulary at 24 months of age showed a significant influence on the maternal input features: the input addressed to children with weak lexical ability was characterised by a higher presence of attention getters (U = 217.00, p = 0.007) and a lower proportion of questions (U = 236.00, p = 0.017) than that of mothers of typically-talking children. CONCLUSIONS AND IMPLICATIONS: At 24 months of age, it seems that the presence of a language delay and not belonging to the clinical group of children with SCTs influences the functional characteristics of the maternal input. It is important to support the parents of children with SCTs during the communication process and later during their child's development, leading them to observe their children's manifested skills rather than looking for possible predicted difficulties. WHAT THIS PAPER ADDS: What is already known on the subject Studies in the literature demonstrated how mothers can generally adapt their input to their child's characteristics. To our knowledge, only two recent studies analysed the maternal input addressed to children with SCT at 8 months of age, highlighting significant differences. What this paper adds to existing knowledge The maternal input addressed to children with SCT at 24 months of age is not different from that addressed to TD children. At 24 months of age, the mothers adapt their input to the verbal competence shown by their child (weak lexical ability versus typically-talking), while belonging to the clinical group does not show an influence. What are the potential or actual clinical implications of this work? All the participants of the present study received prenatal diagnosis disclosure by an expert team of professionals, and they were all involved in a longitudinal study aimed at monitoring the children's development and supporting their parents. These results show that giving clear and complete information about possible development paths to parents of children with SCTs during diagnosis disclosure is crucial. Moreover, supporting the parents during the communication process and later during their child's development is fundamental, leading them to observe their children's manifested skills rather than looking for possible predicted difficulties.

[Prenatal diagnosis and outcome of pregnancy for women with high risks by screening of fetal free DNA from peripheral blood samples].

OBJECTIVE: To analyze the results of prenatal diagnosis and outcome of pregnancy for women with a high risk for fetal aneuploidies. METHODS: A total of 747 cases of prenatal diagnosis by amniocentesis due to high risks by non-invasive prenatal testing (NIPT) were selected from January 2015 to March 2022 in the Drum Tower Hospital Affiliated to Nanjing University Medical School. The amniotic fluid samples were subjected to chromosomal karyotyping and/or chromosomal microarray analysis. All cases were followed up by searching the birth information or telephone calls, and the results were recorded. 2 test or F test were used for comparing the difference between the groups. RESULTS: Among the 747 pregnant women with a high risk by NIPT, 387 were true positives, and the overall positive predictive value (PPV) was 51.81%. The PPVs for trisomy 21 (T21), trisomy 18 (T18), trisomy 13 (T13) and sex chromosome aneuploidies (SCA) were 80.24% (199/248), 60% (48/80), 14% (7/50) and 38.97% (106/272), respectively. The PPV for T21 was significantly higher than T18 and T13 (χ2 = 85.216, P < 0.0001). The PPV for other chromosomal aneuploidies and copy number variations (CNVs) were 11.11% (5/45) and 40.74% (22/52), respectively. The PPV for increased X chromosomes was significantly higher than X chromosome decreases (64.29% vs. 22.22%, χ2 = 5.530, P < 0.05). The overall PPV for elder women (≥ 35 years old) was significantly higher than younger women (69.35% vs. 42.39%, χ2 = 49.440, P < 0.0001). For T21 and T18, the PPV of Z ≥ 10 group was significantly higher than that for 3 ≤ Z < 5 group or 5 ≤ Z < 10 group (P < 0.05). Among 52 cases with a high risk for CNVs, the PPV for the ≤ 5 Mb group was significantly higher than the 5 Mb < CNVs < 10 Mb or > 10 Mb groups (60% vs. 30%60% vs. 23.53%, P < 0.05). Among the 387 true positive cases, 322 had opted for induced labor, 53 had delivered with no abnormal growth and development, and 12 were lost during the follow-up. CONCLUSION: The PPVs for common chromosomal aneuploidies are related to the age and Z value of the pregnant women, which were higher in the elder group and higher Z value group. In addition, the PPV is associated with high risk types. The PPV for T21 was higher than T18 and T13, and that for 45,X was lower than 47,XXX, 47,XYY or 47,XXY syndrome. NIPT therefore has relatively high PPVs for the identification of chromosomal CNVs.

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

OBJECTIVE: 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. METHODS: 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). RESULTS: 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. CONCLUSION: 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.

[Prenatal diagnosis of a fetus with 1p36 deletion syndrome and 3p26.3p25.2 duplication].

OBJECTIVE: To explore the characteristics of a fetus with chromosome 1p36 deletion syndrome and 3p26.3p25.2 duplication. METHODS: A pregnant woman who had attended the Genetic Counseling Clinic of Linyi People's Hospital on February 22, 2022 and her fetus were selected as the study subjects. Clinical data were collected. Chromosomal karyotyping, fluorescence in situ hybridization (FISH) and chromosomal microarray analysis (CMA) were carried out for the prenatal diagnosis. RESULTS: Ultrasonography at 24th gestational week revealed that the fetus had ventricular septal defect, single umbilical artery, and slight widening of left lateral ventricle (12 mm). The woman was found to have a karyotype of 46,XX,t(1;3)(p36.22;p25.2), and the result of FISH was t(1;3)(3pter+,1qter+;1pter+,3qter+). The fetus was found to have a karyotype of 46,X?,add(1)(p36), and CMA confirmed that it has a 9.0 Mb deletion at 1p36.33p36.22 and a 12.6 Mb duplication at 3p26.3p25.2. Combining the maternal karyotype, the molecular karyotype of the fetus was determined as 46,X?,der(1)t(1;3)(p36.22;p25.2)mat.arr[hg19]1p36.33p36.22(849467_9882666)×1, 3p26.3p25.2(61892_12699607)×3, with the former known to be associated with 1p36 deletion syndrome. CONCLUSION: The fetus was diagnosed with 1p36 deletion syndrome, and its 1p36.33p36.22 deletion and 3p26.3p25.2 duplication had both derived from the balanced translocation carried by its mother.

Combined Z-scores to assess the impact of rare autosomal trisomies that results in non-invasive prenatal screening on pregnancy outcomes.

OBJECTIVE: This study aimed to combine Z-scores to evaluate the effects of rare autosomal trisomies (RATs) in non-invasive prenatal screening (NIPS) on pregnancy outcomes at a single center. METHODS: We retrospectively collected the clinical data of women with high-risk RATs results using NIPS at a single center between January 2017 and December 2021. NIPS-positive results were separated into three groups based on the Z-value of RATs (Group1: 6 ≤ Z < 10; Group2: 10 ≤ Z < 15; Group 3: Z ≥ 15). Pregnancy outcomes of women with RATs were compared with the low-risk NIPS group. RESULTS: Overall, 83 RATs were identified in 23,321 NIPS results at our center. Prenatal diagnosis was conducted for 55 patients, and no case was confirmed, with a positive predictive value (PPV) of zero. Fifteen of these patients had adverse pregnancy outcomes, including delivered preterm and/or birth weight (9/15, 60.0 %), structural abnormalities (4/15, 26.7 %), miscarriage (1/15, 6.7 %), and intrauterine death (1/15, 6.7 %). There were 8 (8/22, 36.4 %) adverse pregnancy outcomes in Group 3, which was significantly higher than that in the low-risk NIPS group (p < 0.01). No significant difference was observed between the control group and Group 1 and Group 2 (p > 0.01). CONCLUSIONS: Clinicians should pay more attention to the RATs results when the Z-score is ≥ 15. The data are available for clinicians to guide the prenatal diagnosis of RATs and pregnancy management.

Chromosomal abnormalities study for anembryonic pregnancy by BACs-on-Beads technique.

OBJECTIVE: This study evaluated the BACs-on-Beads™ (BoBs) efficiency assay in detecting chromosomal anomalies in products of conception (POC) specimens associated with anembryonic pregnancy (AP) among Thai pregnant women. METHOD: Retrospective analysis applied the BoBs™ assay to examine AP samples from 2010 to 2022. The incidences of AP with chromosomal abnormalities were reported. RESULT: Assessment of villi from anembryonic pregnancy samples found normal chromosome complement in 50% of the cases, while the remainder showed chromosomal abnormalities. Trisomy 16 was found in 15% of the cases and trisomies 22, 15, and 19 in 9.6%, 3.8%, and 3.8%, respectively. Advanced maternal age was associated with a higher incidence of aneuploidy. CONCLUSION: The BoBs™ assay effectively detected diverse chromosomal abnormalities in villi samples from POC. The diagnostic utility of the BoBs™ assay was highlighted in identifying chromosomal irregularities in AP cases. Trisomy 16 possessed the most chromosomal abnormalities in the AP samples.

Clinical course and genetic analysis of a case of the amniocentesis showing chromosome 6 trisomy mosaicism.

OBJECTIVE: Herein, we present a case of mosaic trisomy 6 detected by amniocentesis. CASE REPORT: Amniocentesis (G-banding) was performed at 17 weeks of gestation; the results were 47,XY,+6[3]/46,XY[12]. Fetal screening ultrasonography showed no morphological abnormalities, and the parents desired to continue the pregnancy. The infant was delivered vaginally at 39 weeks' gestation. The male infant weighed 3002 g at birth with no morphological abnormalities. G-banding karyotype analysis performed on the infant's peripheral blood revealed 46,XY[20]. FISH analysis revealed trisomy signals on chromosome 6 in 1-4 out of 100 cells from the placenta. The single nucleotide polymorphism microarray of the umbilical cord blood revealed no abnormalities. Methylation analysis of umbilical cord blood revealed no abnormalities in PLAGL1. No disorders were observed at one year of age. CONCLUSION: When amniocentesis reveals chromosomal mosaicism, it is essential to provide a thorough fetal ultrasound examination and careful genetic counseling to support the couples' decision-making.

Relationships among maternal monosomy X mosaicism, maternal trisomy, and discordant sex chromosome aneuploidies.

OBJECTIVE: To explore the impact of maternal factors on the false-positive fetal sex chromosome aneuploidies (SCAs) results obtained through noninvasive prenatal screening (NIPS). METHODS: We retrospectively analyzed pregnant women with high-risk SCAs as revealed using NIPS between January 2017 and December 2022. Clinical data such as results of invasive prenatal diagnoses, copy number variation sequencing (CNV-seq) and pregnancy outcomes were analysed. RESULTS: Overall, 177 (0.6 %) women with SCA-positive results were collected from 27,941 patients who had undergone NIPS. Among them, 110 (62.2 %) pregnant women chose prenatal diagnosis and 39 (35.5 %) cases were confirmed. For the women with monosomy X false-positive results from the NIPS, 53.1 % (17/32) were found to be maternal mosaicism monosomy X. In cases with 47, XXX false-positive results, 60 % (6/10) of them were maternal 47,XXX (5 cases) or maternal mosaicism 47,XXX (1 case). One (1/6, 16.7 %) case of maternal mosaicism monosomy X was detected in the false positive results of 47, XXY/47, XYY revealed. The incidence rate of maternal sex chromosome abnormalities was positively correlated with the Z-score of ChrX. When the Z-score of ChrX ≥ 15, more than 50 % of pregnant women were found to be maternal sex chromosome abnormalities, and when Z-score ≥ 30, the incidence rate was as high as 100 %. CONCLUSIONS: Maternal monosomy X mosaicism and trisomy X respectively played an important role in the discordance of 45, X and 47, XXX revealed by NIPS. CNV-seq was recommended for the pregnant women at risk of maternal sex chromosome abnormalities, which could help clinicians to provide more accurate and efficient advice during genetic counseling and to guide appropriate prenatal diagnosis strategy for the next pregnancy.

Low-level mosaic trisomy 7 at amniocentesis in a pregnancy associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the trisomy 7 cell line and a favorable fetal outcome.

OBJECTIVE: We present low-level mosaic trisomy at amniocentesis in a pregnancy associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the trisomy 7 cell line and a favorable fetal outcome. CASE REPORT: A 40-year-old, primigravid woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY in cultured amniocytes. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (7) × 2-3, (X,Y) × 1, consistent with 24% mosaicism for trisomy 7. Polymorphic DNA marker analysis on the DNA extracted from the uncultured amniocytes and parental bloods excluded uniparental disomy (UPD) 7. Prenatal ultrasound findings were normal. She was referred for genetic counseling at 19 weeks of gestation. No repeat amniocentesis was suggested, and continuing the pregnancy was advised. At 22 weeks of gestation, the result of soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) = 6.1 (normal < 38). She did not have preeclampsia. At 39 weeks of gestation, a 3346-g male baby was delivered without any phenotypic abnormality. aCGH analysis on the DNA extracted from cord blood and placenta revealed the result of arr (1-22) × 2, (X,Y) × 1 with no genomic imbalance in all tissues. When follow-up at age three months, the baby was normal in development and phenotype. The peripheral blood had a karyotype of 46,XY, and interphase fluorescence in situ hybridization (FISH) analysis using the bacterial artificial chromosome (BAC) probes of chromosome 7 showed disomy 7 cells in all 102/102 cells. CONCLUSION: Low-level mosaic trisomy 7 at amniocentesis can be associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the trisomy 7 cell line and a favorable fetal outcome.

Genetic counseling of non-invasive prenatal testing (NIPT) trisomy 7-positive pregnancies.

Trisomy 7 is the most common observed type of rare autosomal trisomies (RATs) detected at expanded genome-wide non-invasive prenatal testing (NIPT). Genetic counseling of NIPT trisomy 7-positive pregnancies remains to be not easy because the parents may worry about the likelihood of adverse pregnancy outcomes, fetal abnormality and the necessity of invasive procedures for confirmation of fetal mosaic trisomy 7 and uniparental disomy (UPD) 7. This review provides a comprehensive information on the update issues concerning genetic counseling of NIPT trisomy 7-positive pregnancies.

Use of the MS-MLPA assay in prenatal diagnosis of Prader-Willi syndrome with mosaic trisomy 15.

OBJECTIVE: We present a prenatal diagnosis strategy of using Methylation-Specific Multiplex Ligation-Dependent Probe Amplification (MS-MLPA) for the detection of maternal uniparental disomy 15/trisomy 15 (UPD(15) mat/T15) mosaicism. CASE REPORT: A 43-year-old woman underwent amniocentesis at 19 weeks of gestation due to a high risk of trisomy 15 (T15) as indicated by non-invasive prenatal testing (NIPT). Cytogenetic analysis revealed a karyotype of 46, XX of cultured amniocytes. Further analysis using copy number variation sequencing (CNV-seq) analysis showed 55 % T15 mosaicism. The second amniocentesis was performed and showed a karyotype of 46, XX and 26 % T15 mosaicism by interphase fluorescence in situ hybridization (FISH). MS-MLPA analysis of uncultured amniocytes showed that the copy number ratio of 15q11-13 ranged from 1.3 to 1.5, and the percentage of methylation was between 70 % and 100 %. MS-MLPA assay of cultured amniocytes showed a copy number ratio of 1 and a methylation percentage of 100 %. Therefore, this fetus was identified to be an UPD(15) mat/T15 mosaicism. The parents decided to terminate the pregnancy. CONCLUSION: MS-MLPA can be used in combination with karyotype and CNV-seq for prenatal diagnosis of NIPT high-risk T15 to avoid missed diagnosis of UPD(15) mat/T15 mosaicism.

Comprehensive phenotyping of fetuses with trisomy 18: a perinatal center experience.

Trisomy 18 is the second most common aneuploidy after trisomy 21. It presents with varying degrees of heterogeneous clinical phenotypes involving multiple organ systems, with a high mortality rate. Clinical assessment of fetal trisomy 18 is always challenging. In this study, we describe the phenotypes of the fetuses with trisomy 18 from a perinatal cohort. We reviewed fetuses with trisomy 18 in referrals for perinatal autopsy over the period of 15 years. A detailed phenotyping of the fetuses with trisomy 18 was executed by perinatal autopsy. Appropriate fetal tissues were obtained to perform genomic testing. We observed trisomy 18 in 16 fetuses (2%) in our cohort of 784 fetal/neonatal losses and a perinatal autopsy was performed on all of them. Abnormal facial profile was the most frequent anomaly (10/16, 62%) followed by anomalies of the extremities (9/16, 56%), and cardiac defects (6/16, 37%). We also observed esophageal atresia, diaphragmatic hernia, and neural tube defect. The study represents one of the largest cohorts of trisomy 18 from a perinatal center from a developing country and highlights the clinical heterogeneity attributed to trisomy 18. We also report a recurrence of trisomy 18 in a family.

Prenatal Genome-Wide Cell-Free DNA Screening: Three Years of Clinical Experience in a Hospital Prenatal Diagnostic Unit in Spain.

Genome-wide prenatal cell-free DNA (cfDNA) screening can be used to screen for a wide range of fetal chromosomal anomalies in pregnant patients. In this study, we describe our clinical experience with a genome-wide cfDNA assay in screening for common trisomies, sex chromosomal aneuploidies (SCAs), rare autosomal aneuploidies (RAAs), and copy-number variations (CNVs) in about 6000 patients over a three-year period at our hospital's Prenatal Diagnostic Unit in Spain. Overall, 204 (3.3%) patients had a high-risk call, which included 76 trisomy 21, 21 trisomy 18, 7 trisomy 13, 29 SCAs, 31 RAAs, 31 CNVs, and 9 cases with multiple anomalies. The diagnostic outcomes were obtained for the high-risk cases when available, allowing for the calculation of positive predictive values (PPVs). Calculated PPVs were 95.9% for trisomy 21, 77.8% for trisomy 18, 66.7% for trisomy 13, 10.7% for RAAs, and 10.7% for CNVs. Pregnancy and birth outcomes were also collected for the majority of RAA and CNV cases. Adverse perinatal outcomes for some of these cases included preeclampsia, fetal growth restriction, preterm birth, reduced birth weight, and major congenital structural abnormalities. In conclusion, our study showed strong performance for genome-wide cfDNA screening in a large cohort of pregnancy patients in Spain.