Prenatal diagnosis of fetuses with Emanuel syndrome: Results of ultrasound examination and invasive genetic testing.

OBJECTIVE: To investigate prenatal manifestations of Emanuel syndrome (ES) by retrospectively analyzing the results of prenatal diagnosis. METHODS: Thirteen fetuses were collected from five hospitals, of which six were confirmed with 47,der(22)t(11;22; ES) by karyotype and chromosomal microarray analysis (CMA). Seven were diagnosed with 46,t(11;22) balanced translocations by karyotype, including one de novo mosaic 46,XX,t(11;22). In 3/7, CMA was performed but did not identify chromosomal imbalances. The results of prenatal diagnoses were reviewed, including ultrasound examinations and genetic testing. RESULTS: In ES fetuses, the derivative 22 was consistently inherited from the mother, while in the balanced translocation group, the t(11;22) chromosome was of paternal origin in 3/6 cases, All ES fetuses presented with multiple abnormalities by ultrasound examinations. Diaphragm hernia (3/6), Dandy-Walker complex (3/6), and kidney aplasia (3/6), were the most common ultrasound findings. Sonographic soft markers such as increased nuchal translucency, increased nuchal fold thickness appeared in 3 cases and all of these were associated with other anomalies. However, none of the ultrasound findings differentiated ES from other genetic syndromes during fetal period. CONCLUSIONS: In this series, in fetuses with a der(22), the derivative chromosome was consistently of maternal origin. In contrast, 46,t(11;22) balanced translocations were of maternal or paternal origin. The results contribute to the literature regarding the fetal phenotype of ES. Due to the absence of specific features distinguishing ES from other genetic syndromes, confirming the diagnosis through invasive genetic testing is necessary.

Case Report: Low-Level Maternal Mosaicism of a Novel CREBBP Variant Causes Recurrent Rubinstein-Taybi Syndrome in Two Siblings of a Chinese Family.

Familial Rubinstein-Taybi syndrome (RSTS) with recurrent RSTS siblings and apparently unaffected parents is rare; such cases might result from parental somatic and/or germline mosaicism. Parental low-level (<10%) germline mosaicism in the CREBBP-associated RSTS family has not been reported. Here, we present our studies of a Chinese family with two RSTS siblings and apparently unaffected parents. We detected the apparent de novo variant (DNV) c.3235C>T (p.Gln1079*) in CREBBP in the siblings via trio whole-exome sequencing. High-depth next-generation sequencing (NGS) for the parents revealed a low-level (<10%) mosaic variant in both the peripheral blood (3.64%) and buccal mucosa (1.94%) of the unaffected mother, indicating maternal somatic and germline mosaicism. Peripheral blood RNA-sequencing analysis for the patients and normal individuals indicated that the c.3235C>T (p.Gln1079*) non-sense variant did not trigger nonsense-mediated mRNA decay to reduce CREBBP mRNA levels. Transcriptome analysis revealed 151 downregulated mRNAs and 132 upregulated mRNAs between the patients and normal individuals. This study emphasizes that high-depth NGS using multiple specimens might be applied for a family with an affected sibling caused by an apparent CREBBP DNV to identify potential low-level parental mosaicism and provide an assessment of recurrence risk.

Intrauterine phenotypic features associated with 16p11.2 recurrent microdeletions.

OBJECTIVE: To investigate the detection rate of 16p11.2 recurrent microdeletions in fetuses with abnormal ultrasound findings and determine the common abnormal ultrasound findings in fetuses carrying the deletion. METHODS: This study reviewed 2262 consecutive fetuses with abnormal ultrasound findings who underwent prenatal chromosomal microarray analysis between October 2014 and December 2016. Cases carrying the 16p11.2 recurrent microdeletion were further genetically analyzed, and their clinical features were reviewed. RESULTS: The 16p11.2 recurrent microdeletion was identified in 12 fetuses, who had skeletal malformations (5/12), cardiovascular malformations (4/12), or isolated ultrasound markers (3/12). Approximately 0.5% (12/2262) of the fetuses with abnormal ultrasound findings harbored the deletion. The 5 fetuses with skeletal malformations displayed vertebral defects, particularly in the hemivertebra and butterfly vertebra. The detection rate of the 16p11.2 recurrent microdeletion was statistically significant (P < .05) among fetuses with skeletal malformations (3.6%, 5/140), fetuses with cardiovascular malformations (1.1%, 4/367), and fetuses with isolated ultrasound markers (0.4%, 3/702). CONCLUSION: The most frequent ultrasound findings in fetuses with 16p11.2 recurrent microdeletions are skeletal malformations (particularly vertebral malformations), followed by cardiovascular malformations, and isolated ultrasound markers.

An SNP panel for the analysis of paternally inherited alleles in maternal plasma using ion Torrent PGM.

Researchers have sought to develop an effective protocol for paternity analysis using cell-free DNA (cfDNA) in maternal plasma. The use of massively parallel sequencing (MPS) technology for SNP testing is attractive because of its high-throughput capacity and resolution to single-base precision. In this study, we designed a customized SNP panel for cfDNA sequencing that includes 720 short amplicons (< 140 bp) targeting SNPs on the autosome and Y chromosome. The systemic performance was evaluated using the Ion Torrent PGM, indicating balanced coverage among most of the included loci, except for 78 poorly performing SNPs that were observed to have an inconsistent allele balance, lower coverage reads or high background signals. Then, the custom panel was used to perform cfDNA genotyping in maternal plasma from 20 pregnancies in the first and second trimesters (9 to 21 weeks). By establishing an allele fraction cutoff of 2.0%, 53 to 128 autosomal SNP loci were considered informative for paternal origin. Validation results in foetal samples showed that 49.43% to 100% of the real paternal alleles were accurately identified, with incorrect alleles encountered in 3 cases. The concentration of foetal cfDNA ranged from 4.28% to 10.70%. Our results show that this amplicon-based sequencing strategy could be utilized in analysing paternally inherited alleles in maternal plasma. However, further studies and optimization are required for a more detailed and accurate interpretation of the cfDNA sequencing results based on MPS technology.

[Prenatal genetic analysis of two fetuses with Miller-Dieker syndrome].

OBJECTIVE: To perform molecular cytogenetic study on two fetuses with abnormal ultrasound findings and analyze their genotype-phenotype correlation. METHODS: G-banded karyotyping, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed on amniotic fluid cells from both fetuses and peripheral blood samples from their parents. Results of SNP array were analyzed with bioinformatics software. RESULTS: G-banded karyotyping failed to detect any abnormalities in both fetuses and their parents. SNP array detected a 2.484 Mb terminal deletion at 17p13.3 [arr[hg19] 17p13.3 (83 035-2 567 405)×1] in fetus 1 and a 3.295 Mb terminal deletion at 17p13.3p13.2 [arr[hg19] 17p13.3p13.2 (83 035- 3 377 560)×1] in fetus 2. Both deletions have overlapped with the critical region of Miller-Dieker syndrome (MDS) and involved candidate genes such as PAFAH1B1, YWHAE and CRK. In addition, SNP array and FISH analyses on the parental peripheral blood samples demonstrated that both 17p13.3 and 17p13.3p13.2 deletions were of de novo origin. Metaphase FISH performed on amniotic fluid cells confirmed the presence of 17p13.3 and 17p13.3p13.2 deletions detected by the SNP array, while metaphase FISH performed on the parents excluded any potential chromosome rearrangements. CONCLUSION: Abnormal ultrasound features for fetuses with MDS mainly include central nervous system anomalies. SNP array can efficiently detect 17p13.3 microdeletions underlying MDS, and accurately map the breakpoints and involved genes, which may facilitate understanding of the genotype and phenotype correlations for MDS.

Chromosome 10q26 deletion syndrome: Two new cases and a review of the literature.

The current study presents the cases of two unrelated patients with similar clinical features, including craniofacial anomalies, developmental delay/intellectual disability and cardiac malformations, that are consistent with chromosome 10q26 deletion syndrome. High­resolution single­nucleotide polymorphism analysis revealed that 10q26 terminal deletions were present in these two patients. The locations and sizes of the 10q26 deletions in these two patients were compared with the locations and sizes of 10q26 deletions in 30 patients recorded in the DECIPHER database and 18 patients characterized in previous studies through chromosomal microarray analysis. The clinical features and locations of the 10q26 deletions of these patients were reviewed in an attempt to map or refine a critical region (CR) for phenotypes. Additionally, the association between previously suggested CRs and phenotypic variability was discussed. The current study emphasize that a distal 10q26 terminal deletion with a breakpoint at ~130 Mb may contribute to the common clinical features of 10q26 deletion syndrome.

[Application of single nucleotide polymorphism-based array analysis for prenatal diagnosis of a fetus with de novo derivative chromosome].

OBJECTIVE: To analyze a fetus with increased nuchal translucency and nuchal fold, and to assess the recurrence risk for her family and provide a basis for prenatal diagnosis. METHODS: G-banded karyotyping and single nucleotide polymorphism-based array (SNP-Array) analysis were used to analyze the fetus and her parents. RESULTS: SNP-Array analysis has detected a 41.04 Mb duplication at Xp22.33p11.4 and a 30.51 Mb duplication at 13q31.3q34 in the fetus. G-banding karyotyping indicated that the fetus had a karyotype of 46,X,der(X)(13qter-13q31::Xp11.4-Xp22.3::Xp22.3-Xqter). Her parents had normal results for both G-banding karyotyping and SNP-Array analysis, suggesting that the fetus has carried a de novo derivative chromosome X. CONCLUSION: SNP-Array combined with G-banding karyotyping is helpful to confirm the composition and connection type of de novo derivative chromosome, which can improve the accuracy of diagnosis and is valuable for the evaluation of recurrence risk.

[Genetic analysis of a fetus with partial 1q monosomy and partial 17q trisomy].

OBJECTIVE: To analyze a fetus with abnormal sonographic features and correlated its genotype with phenotype. METHODS: G-banding analysis, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed for the fetus. Karyotyping and FISH were also carried out for the parents. RESULTS: SNP array detected a 4.4 Mb deletion at 1q44 and a 10.4 Mb duplication at 17q24.3q25.3 in the fetus. Based on the results of SNP array and FISH analysis, the father was diagnosed with a cryptic t(1;17)(q44;q24.3) translocation. The fetus has inherited a der(1)t(1;17)(q44;q24.3) from its father. CONCLUSION: The 1q44 deletion and 17q24.3q25.3 duplication may have contributed to the abnormal sonographic features presented by the fetus.

[Prenatal diagnosis of 1p36.3 microdeletion in a fetus with complex heart defect].

OBJECTIVE: To analyze a fetus presenting with complex heart defect and assess the recurrence risk. METHODS: Conventional karyotyping, fluorescence in situ hybridization (FISH) and single nucleotide polymorphism-based array (SNP-array) were used to analyze the fetus and his parents. RESULTS: SNP-array has detected a 6.9 Mb microdeletion at 1p36.33-p36.23 in the fetus. Chromosomal and FISH analyses indicated that the father of the fetus had a karyotype of 46,XY,t(1;14)(p36.3;p12), and that the fetus has inherited an abnormal chromosome 1 derived from the paternal translocation. CONCLUSION: SNP-array combined with GTG banding and FISH can help to detect cryptic translocation, microdeletion or microduplication of chromosomes and is valuable to assess the recurrence risk for the affected family.

Single nucleotide polymorphism-based microarray analysis for the diagnosis of hydatidiform moles.

In clinical diagnostics, single nucleotide polymorphism (SNP)-based microarray analysis enables the detection of copy number variations (CNVs), as well as copy number neutral regions, that are absent of heterozygosity throughout the genome. The aim of the present study was to evaluate the effectiveness and sensitivity of SNP­based microarray analysis in the diagnosis of hydatidiform mole (HM). By using whole­genome SNP microarray analysis, villous genotypes were detected, and the ploidy of villous tissue was determined to identify HMs. A total of 66 villous tissues and two twin tissues were assessed in the present study. Among these samples, 11 were triploid, one was tetraploid, 23 were abnormal aneuploidy, three were complete genome homozygosity, and the remaining ones were normal ploidy. The most noteworthy finding of the present study was the identification of six partial HMs and three complete HMs from those samples that were not identified as being HMs on the basis of the initial diagnosis of experienced obstetricians. This study has demonstrated that the application of an SNP­based microarray analysis was able to increase the sensitivity of diagnosis for HMs with partial and complete HMs, which makes the identification of these diseases at an early gestational age possible.

[Prenatal genetic diagnosis for a fetus with atypical neurofibromatosis type 1 microdeletion].

OBJECTIVE: To analyze the correlation between atypical neurofibromatosis type 1(NF1) microdeletion and fetal phenotype. METHODS: Fetal blood sampling was carried out for a woman bearing a fetus with talipes equinovarus. G-banded karyotyping and single nucleotide polymorphism array (SNP-array) were performed on the fetal blood sample. Fluorescence in situ hybridization (FISH) was used to confirm the result of SNP array analysis. FISH assay was also carried out on peripheral blood specimens from the parents to ascertain the origin of mutation. RESULTS: The karyotype of fetus was found to be 46, XY by G-banding analysis. However, a 3.132 Mb microdeletion was detected in chromosome region 17q11.2 by SNP array, which overlaped with the region of NF1 microdeletion syndrome. Analyzing of the specimens from the fetus and its parents with FISH has confirmed it to be a de novo deletion. CONCLUSION: Talipes equinovarus may be an abnormal sonographic feature of fetus with atypical NF1 microdeletion which can be accurately diagnosed with SNP array.

Smith­Magenis syndrome in monozygotic twin fetuses presenting with discordant phenotypes and uteroplacental insufficiency.

Smith­Magenis syndrome (SMS) is a rare condition with multiple congenital malformations caused by the haploinsufficiency of RAI1 (deletion or mutation of RAI1). However, the correlation between genotype and phenotype is not well understood. The present study describes the prenatal diagnosis of monozygotic twins with a 17p11.2 deletion, which is indicative of SMS, who presented with discordant phenotypes and uteroplacental insufficiency. A high­resolution genome­wide single nucleotide polymorphism array revealed a 3.7­Mb deletion in the 17p11.2 chromosome region. Accurate breakpoints of the deletion in these patients were used to identify correlations between SMS and the concomitant phenotypes, particularly uteroplacental insufficiency, which has rarely been investigated in SMS. In addition, no exonic mutations were identified in or affected known disease­associated loci that could explain the congenital anomalies, according to a model that accounts for the possibility of incomplete penetrance. Furthermore, a novel benign copy number variation (a duplication of 195 kb at 13q12.13) was identified but was unlikely to be clinically significant in the discordant phenotypes of the twins. The present study showed that multiple interacting genetic and environmental factors are involved in determining the variance of the SMS phenotype.

[Chromosomal microarray analysis for lateral ventriculomegaly in fetus].

OBJECTIVE: To investigate the relationship between fetal lateral ventriculomegaly and chromosomal microarray analysis (CMA) abnormalities. METHODS: Fifty fetuses with lateral ventriculomegaly detected by ultrasound and a normal karyotype were included. Forty four fetuses were classified as mild ventriculomegaly (MVM), in which the lateral ventricular atrium was 10-15 mm. Six had severe ventriculomegaly (SVM), with the lateral ventricularatrium being ≥ 15 mm. The fetuses were also divided into isolated (n= 21) and non-isolated groups (n= 29) based on whether they are associated with other anomalies. RESULTS: Thirteen (26%) of the fetuses were found to be abnormal by CMA. For the 44 cases with MVM, 9 (20.9% ) were found to be abnormal, while for the 6 cases with SMV, 4 (66.7%) were found to be abnormal (P>0.05). CMA abnormalities were found in 2 (9.5%) of the 21 fetuses with isolated ventriculomegaly group and 11 (37.9%) of the 29 fetuses with non-isolated ventriculomegaly group (P<0.05). CONCLUSION: Chromosome microdeletions and microduplications are the most common abnormalities found in fetal lateral ventriculomegaly. When ventriculomegaly is associated with other anomalies, the incidence of CMA abnormally is much higher. Prenatal diagnosis is necessary for fetuses with lateral ventriculomegaly.

[Misdiagnosis of mosaic tetrasomy 9p in a fetus by single nucleotide polymorphism-based array].

OBJECTIVE: To explore the reason for discordant results of karyotyping and microarray analysis in a fetus with mosaic tetrasomy 9p. METHODS: Amniocentesis was carried out for a pregnant woman with advanced age for whom ultrasound scan has indicated fetal ventricular expansion, intrauterine growth retardation and persistent upper venous cavity. G-banded karyotyping and single nucleotide polymorphism-based arrays (SNP-array) analysis were performed at the same time. RESULTS: Analysis of amniocytic chromosome has suggested mosaic tetrasomy 9p (47,XX,+psu idic(9)(q21)[23]/46,XX[27]). While SNP-array has detected a non-mosaic trisomy 9p with a 68.7 Mb duplication at 9p24.3q21.11. The results of the two methods were therefore discordant. CONCLUSION: SNP-array will analyze genetic material in the form of numbers rather than morphology. For chimeras containing two types of cell lines, when the mosaic rate was close to 50% and the average amount of genetic material of the chimeras was equivalent to the amount of genetic material of non-chimeras, microarray analysis may come to the conclusion of a non-mosaic heteroploidy. Therefore, microarray results for large segment chromosome abnormalities should be combined with the results of G-banded karyotyping for genetic counseling.

[Prenatal diagnosis of five cases of monochorionic-diamniotic twins discordant for karyotype analysis].

OBJECTIVE To explore the mechanism and diagnostic method for monochorionic-diamniotic twins discordant for karyotype analysis. METHODS Dual amniocentesis was performed on five pairs of monochorionic-diamniotic twins, which all consisted of a normal twin and one with multiple malformations revealed by ultrasound. Karyotype analysis was performed on amniocytes derived from each of the twins. Zygosity was also determined with DNA extracted from amniocytes with 16 polymorphic microsatellite markers. RESULTS Three cases of 45,X, one case of 47,XX,+9 and one case of 47,XY,+18 were detected among the abnormal twins, while the normal fetuses all had a normal karyotype. DNA analysis suggested that, in all cases, the twins have shared the 16 polymorphic microsatellite markers, which confirmed their monozygosity. CONCLUSION Monochorionic-diamniotic twins may be discordant for karyotyping, for which anaphase lagging, chromosomal non-disjunction and trisomy rescue may be the underlying reasons. As a simple method, dual amniocentesis can be used to obtain amniotic fluid samples for karyotype analysis and determination of zygosity for such twins.

Improved assay performance of single nucleotide polymorphism array over conventional karyotyping in analyzing products of conception.

BACKGROUND: Conventional karyotyping has been a routine method to identify chromosome abnormalities in products of conception. However, this process is being transformed by single nucleotide polymorphism (SNP) array, which has advantages over karyotyping, including higher resolution and dispensing with cell culture. Therefore, the purpose of this study was to evaluate the advantage of high-resolution SNP array in identifying genetic aberrations in products of conception. METHODS: We consecutively collected 155 products of conception specimens, including 139 from first-trimester miscarriage and 16 from second-trimester miscarriage. SNP array was performed on these samples in parallel with G-banded karyotyping. RESULTS: The test success rate was 98.1% (152/155) using SNP array, which was higher than that using karyotyping (133/155, 85.8%). It yielded a 63.8% (97/152) abnormality rate, and the frequency of various chromosome abnormalities was in agreement with other previous studies. The results between array and karyotyping demonstrated a 94.0% (125/133) concordance. SNP array obtained additional aberrations in 3.8% (5/133) of those cases unidentified by karyotyping, which included three cases with whole-genome uniparental disomy, one with pathogenic copy number variation, and one with del(4)(q35.1q35.2) and dup(12)(q24.31q24.33). However, chromosome translocations presented in two cases and tetraploidy presented in one case were detected by karyotyping instead of array. Additionally, two out of three cases with mosaic trisomy were revealed by array but recognized as pure trisomy by karyotyping. CONCLUSION: This study demonstrated that SNP array had certain advantages over G-banded karyotyping, including a higher success rate, additional detection of copy number variations and uniparental disomy, and improved sensitivity to mosaicism. Therefore, it would be an alternative method to karyotyping in clinical genetic practice.

[Confirmation of a maternal cryptal balanced translocation through analysis of a fetus using microarray].

OBJECTIVE: To analyze a fetus with heart defects and to assess the recurrence risk for her family. METHODS: Single nucleotide polymorphism-based arrays (SNP-Array) analysis using Affymetrix Genome Wide Human SNP CytoHD was performed to analyze the fetus and her parents. Karyotype analysis was also carried out. RESULTS: SNP-Array has detected a 14.5 Mb duplication at 9p and a 14.7 Mb deletion at 11q. Karyotype analysis indicated that the fetus' mother has a karyotype of 46, XX, t(9;11) (p23;q24). Therefore, the fetus has inherited a derivative chromosome 11 derived from the maternal translocation, and her karyotype was 46, XX, der(11) t(9;11) (p23;q24) mat. CONCLUSION: SNP-Array combined with high resolution GTG banding has confirmed that the fetus has a derivative chromosome 11 derived from her mother's balanced translocation, resulting in partial 9p trisomy and partial 11q monosomy. This couple therefore have a high recurrence risk. SNP-Array is capable of detecting small chromosomal imbalance in abnormal fetuses and can pinpoint the breakpoints. It therefore has the advantage for the detection of unbalanced translocation which is difficult to detect with GTG banding, which is important for assessment the recurrence risk for cryptic balanced translocation carriers.

When Cri du chat syndrome meets Edwards syndrome.

It has been well established that the 5p deletion causes Cri du chat syndrome, typically characterized by a cat­like cry, and that duplication of 18q causes Edwards syndrome; the two are rare genetic abnormalities that separately lead to physical and mental impairments. However, the severity of the clinicopathological characteristics that arise when these two aberrations occur in one patient is unknown. Here, the first case in our knowledge of a single patient (a two­year­old female) with 5p partial monosomy and 18q partial trisomy is described. In the present study, chromosome microarray analysis was performed, which identified the imbalance of chromosomes 5 and 18 in the patient. The chromosome aberrations were further confirmed by fluorescence in situ hybridization. By comparing the phenotypes of combined case with those of the individual syndromes, severe clinical phenotypes of the 5p (5p15.33­p13.3) deletion were confirmed, however, the net effect of the duplication of 18q22.3­q23 was not determined, as this duplication only appeared to have a weak effect on the patient's phenotypes. The correlation between these chromosomal aberrations and their clinical features has implications for the identification of critical regions of 5p and 18q, particularly for the functional mapping of chromosome 18.

[Cytogenetic and molecular study of a patient with severe oligozoospermia and asthenozoospermia].

OBJECTIVE: To explore genetic etiologies of a patient with severe oligozoospermia and asthenozoospermia. METHODS: G-banded karyotyping and fluorescence in situ hybridization (FISH) were used to characterize the origin and structure of the abnormal chromosome discovered in this patient. Multiplex polymerase chain reaction (PCR) was used to detect microdeletion of azoospermia factor (AZF). RESULTS: G-banding revealed a karyotype of 45,X,der(15) (?::p11.2→ qter)dn for the patient. Dual-color FISH confirmed that SRY gene was present in a segment attached to the short arm of chromosome 15. Sex chromosome mosaicism and numerical abnormality therefore were both present. Dual-color FISH revealed karyotype of nuc ish(DXZ1× 1, SRY× 1)[390/400]/(DXZ1× 2, SRY× 1) [10/400]. Four-color FISH showed that the abnormal chromosome 15 has derived from a pseudodicentric (Y;15) translocation, and that the breakpoint on Y chromosome was located at Yq12. G-banding and FISH results confirmed that the karyotype was 45,X,der(15)(?::p11.2→ qter)dn.ish psu dic(15;Y)(p11.2;q12)(D15Z1+ , SNRPN+ , PML+ ; SRY+ , DYZ3+ , DYZ1+ ). Microdeletion of AZFc combined with sY254 deletion was detected by multiplex PCR. CONCLUSION: Cytogenetic and molecular genetic analysis of the patient has indicated meiotic disturbances with spermatogenetic arrest resulting from a pseudodicentric chromosome derived from Y;15 translocation and spermatogenesis dysfunction resulting from partial deletion of AZFc region.

[Investigation of ultrasound markers in screening fetal trisomy 21].

OBJECTIVE: To investigate the clinical value of ultrasound markers in screening fetal trisomy 21. METHODS: From Jan. 2001 to Dec. 2011, a retrospective study about sonographic information of 138 fetuses diagnosed as trisomy 21 was taken in the First Affiliated Hospital of Sun Yat-sen University. All fetuses were divided into 3 groups: isolated ultrasound markers, non-isolated ultrasound markers, and isolated structural malformations or other abnormalities. The relationship between trisomy 21 and ultrasound markers as well as structural anomalies or other abnormalities was analyzed. RESULTS: Sonographic anomalies were detected in 132 fetuses (95.7%, 132/138), including ultrasound markers and structural malformations or other abnormalities. One hundred and twenty cases (87.0%, 120/138) had ultrasound markers, 38 (31.7%, 38/120) had one marker and 82 (68.3%, 82/120) had more than one marker (P < 0.01). Fifty-one fetuses (37.0%, 51/138) had isolated ultrasound markers and non-isolated markers were found in 69 fetuses (50.0%, 69/138). Only 12 fetuses (8.7%, 12/138) had isolated structural malformations or other abnormalities. In 20 fetuses on whom the first-trimester ultrasound screening were performed, all had ultrasound markers, 95% (19/20) had thickened nuchal translucency and 55% (11/20) had nasal bone hypoplasia. The most common ultrasound markers on the second-trimester screening were nasal bone hypoplasia, which accounted for 41.9% (52/124) cases, followed by thickened nuchal fold (25.0%, 31/124), short femurs and humerus (24.2%, 30/124), echogenic intracardiac focus (16.1%, 20/124), mild ventriculomegaly (15.3%, 19/124), hyperechoic bowel (12.9%, 16/124), mild renal pyelectasis (12.1%, 15/124). Furthermore, the common structural malformations or other abnormalities were as follows: cardiac defects (33.1%, 41/124), digestive system (26.6%, 33/124). CONCLUSIONS: Ultrasound markers are valuable for screening fetal trisomy 21. The fetuses of trisomy 21 usually had more than one ultrasound markers or associated with other abnormalities. Combinations of ultrasound markers with the results of serum screening and maternal age are necessary for evaluation.