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, ultrasound findings, and pregnancy outcome of 17q12 deletion and duplication syndromes: a retrospective case series.

OBJECTIVE: Analyze the ultrasound findings, single-nucleotide polymorphism array (SNP-array) results, and pregnancy outcomes of fetuses with 17q12 deletions and duplications in the second and third trimesters. Explore the prenatal ultrasound characteristics and pregnancy outcomes of these fetuses. METHODS: Retrospective data were collected for 16 fetuses diagnosed with 17q12 deletion and seven fetuses with 17q12 duplication through SNP-array during prenatal diagnosis at a single Chinese tertiary medical center from January 2017 to December 2023. Maternal demographics, ultrasound findings of the fetuses, SNP-array results, pregnancy outcomes, and follow-up information were reviewed and analyzed. Peripheral blood from the parents was extracted to determine whether the CNVs in the fetuses were inherited or de novo. RESULTS: The copy-number variation (CNV) sizes ranged from 1.39 to 1.94 Mb in cases of 17q12 deletion and from 1.42 to 1.91 Mb in cases of 17q12 duplication. These CNVs included 15 OMIM genes, such as HNF1B, LHX1, and ACACA. In fetuses with a 17q12 deletion, the primary manifestation was renal abnormalities (93.8%, 15/16). Of these, 13 cases (81.3%, 13/16) exhibited bilateral or unilateral hyperechogenic kidneys, and 12 cases (75%, 12/16) had multicystic hyperechogenic kidneys. Two cases (12.5%, 2/16) showed multiple organ structural abnormalities. In fetuses with a 17q12 duplication, four cases (57.1%, 4/7) revealed cardiovascular system abnormalities, including tetralogy of fallot, pulmonary artery stenosis, ventricular septal defect, and tricuspid regurgitation. Two cases (28.6%, 2/7) presented with upper gastrointestinal obstruction. Additionally, one case was particularly unique, characterized by multiple structural malformations, such as ventricular septal defect, microcephaly, cleft lip, and palate. Nine cases opted for pregnancy termination, and 14 chose to continue the pregnancy. Two cases underwent surgical treatment after birth for upper gastrointestinal obstruction, and the prognosis was good. Among the 10 cases of 17q12 deletion, six cases showed consistent prenatal ultrasound findings and postnatal clinical features. Four cases were found to have discrepancies with prenatal ultrasound findings; while the renal ultrasound phenotype appeared normal during the last follow-up, two of these cases were subsequently diagnosed with neuropsychiatric phenotypes. CONCLUSION: Our study expanded the clinical phenotype spectrum of fetuses with 17q12 deletion and duplication, and conducted a preliminary evaluation of prenatal ultrasound findings and postnatal clinical phenotypes in follow-up cases. We further demonstrated a high correlation between fetuses with 17q12 deletion and hyperechogenic, multicystic kidneys. The primary manifestations in fetuses with 17q12 duplication are likely cardiovascular system malformations, which also exhibit a broad spectrum of phenotypic features.

[Clinical characteristics and prenatal diagnosis of fetuses with sex chromosomal aneuploidies detected by non-invasive prenatal testing during early and midterm pregnancies].

OBJECTIVE: To analyze the indication, karyotyping result, ultrasound finding, pregnancy decision and follow-up of fetuses with sex chromosome aneuploidies (SCA) detected by non-invasive prenatal testing (NIPT) during early and midterm pregnancies. METHODS: The results of 225 singleton pregnancies with fetal SCA detected by NIPT were reviewed and analyzed. RESULTS: The 225 cases included 45,X (n=37), 47,XXY (n=74), 47,XXX (n=50), 47,XYY (n=56) and mosaicisms (n=8), among which 121 (53.8%) have opted to terminate the pregnancy, including 45,X (n=31), 47,XXY (n=61), 47,XXX (n=14), 47,XYY (n=12) and 3 mosaicisms. The remainder 104 (46.2%) have elected to continue with the pregnancy, among which three have opted to terminate due to abnormalities detected by ultrasonography, and two had spontaneous abortions. CONCLUSION: NIPT as a first-tier screening method can effectively detect fetal trisomies 21, 13 and 18 as well as SCA. The types of fetal SCA and presence of ultrasound abnormalities are critical factors for the termination of pregnancy.

Noninvasive prenatal screening and diagnosis of two fetuses with Williams syndrome in a cohort of 19,607 pregnancies.

BACKGROUND: This study aimed to evaluate the efficiency of noninvasive prenatal screening (NIPS) technology in screening for microdeletions in the 7q11.23 region. METHODS: 19,607 pregnant women underwent NIPS in our hospital. Maternal peripheral cell-free foetal DNA (cffDNA) was routinely screened for aneuploidy by cffDNA enrichment and simultaneously analyzed for pathogenic copy number variants (CNVs). The Williams syndrome (WS) 7q11.23 region was targeted in this study. Chromosomal microarray analysis (CMA) was used to verify the screen-positive samples. RESULTS: The mean concentration of cffDNA before and after enrichment increased from 9.44% to 19.32%, with a statistically significant difference. Two out of 19,607 samples tested for CNVs were found to have a heterozygous deletion at the 7q11.23 region, indicating a high risk for WS. CMA results confirmed the 1.5 megabase (Mb) deletions at the 7q11.23 region in amniotic fluid samples. One of the two WS foetuses had a small left ventricle by ultrasound screening, and the other did not have a significant cardiovascular abnormality phenotype. CONCLUSIONS: NIPS screening for Williams syndrome can be achieved by enriching cell-free foetal DNA and improving bioinformatic analysis algorithms.

Prenatal diagnosis, pregnancy determination and follow up of sex chromosome aneuploidy screened by non-invasive prenatal testing from 122 453 unselected singleton pregnancies: A retrospective analysis of 7-year experience.

The phenotype of SCA patients are diversities, make prenatal counseling and parental decision-making following the prenatal diagnosis of SCA more complicated and challenging. NIPT has higher sensitivity and specificity in screening trisomy 21 syndrome, but the effectiveness of NIPT in detecting SCA is still controversial. This study is a large-scale retrospective cohort of positive SCA screened from unselected singleton pregnancies by non-invasive prenatal testing (NIPT) from a single prenatal center of a tertiary hospital. Clinical information, indications, diagnostic results, ultrasound findings, pregnancy determinations, and follow-up were reviewed and analyzed. 596 cases of SCA positive were screened out of 122 453, giving a positive detection rate of 0.49%. 510 cases (85.6%) conducted with amniocentesis to detect fetal chromosome, of which 236 were confirmed as true positive of SCA with PPV of 46.3% (236/510). Of the 236 cases confirmed as true positive SCA, 114 cases (48.3%)chose to terminate the pregnancy (93.0%, 65.3%, 15.4% and 10.9% for 45,X, 47,XXY, 47,XXX and 47,XYY, respectively), 122 cases (51.7%) elected to continue the pregnancy. In conclusions, NIPT as a first-tier routine method for screening autosomal aneuploidies, also could play an important role in screening SCA. Low-risk pregnant women are the main indication for the detection of SCA as NIPT test provides to non-selective population. For 47,XXX and 47,XYY with mild phenotype, couples would like to continue the pregnancy. But for 45,X and 47,XXY, parents apt to terminate pregnancy no matter ultrasound abnormalities were found or not.