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1.
Artigo em Inglês | MEDLINE | ID: mdl-32176318

RESUMO

INTRODUCTION: Noninvasive prenatal testing (NIPT), using cell-free fetal DNA, has increasingly been adopted as a screening tool for fetal aneuploidies. Several studies have discussed benefits and limitations of NIPT compared to both ultrasound and invasive procedures, but in spite of some shortcomings NIPT has become extensively used within the last five years. This study aims to describe the current use of NIPT in Europe, Australia and the USA. MATERIAL AND METHODS: We conducted a survey to describe the current use of NIPT. Colleagues filled in a simple email-based questionnaire on NIPT in their own country, providing information on: 1) Access to NIPT, 2) NIPT's chromosomal coverage, 3) financial coverage of NIPT for the patient and 4) the proportion of women using NIPT in pregnancy. Some data are best clinical estimates, due to a lack of national data. RESULTS: In Europe, 14 countries have adopted NIPT into a national policy/program. Two countries (Belgium and the Netherlands) offer NIPT for all pregnant women, whereas most other European countries have implemented NIPT as an offer for higher risk women after first trimester screening. In Australia, either Combined First Trimester Screening (cFTS) or NIPT are used as primary prenatal screening tests. In the USA, there are no national consensus policies on the use of NIPT, however, NIPT is widely implemented. In most European countries offering NIPT, the proportion of women using NIPT is well below 25%. In the Netherlands, Austria, Italy, Spain and most Australian and American States, 25-50% of women have NIPT performed and only in Belgium it is above 75%. In most countries NIPT reports on trisomy 13, 18 and 21, and often also on sex chromosome aneuploidies. Only in Belgium, the Netherlands, Lithuania, Greece, Cyprus and Italy is NIPT offered predominantly as a genome-wide test (including some microdeletions or a whole genome coverage). CONCLUSIONS: NIPT has been widely adopted throughout Europe, Australia and the USA, but only some countries/states have a national policy on the use of NIPT. The variation in NIPT utilization is considerable.

2.
Hum Reprod ; 35(3): 718-726, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-32198505

RESUMO

STUDY QUESTION: Is it possible to haplotype parents using parental siblings to leverage preimplantation genetic testing (PGT) for monogenic diseases and aneuploidy (comprehensive PGT) by genome-wide haplotyping? SUMMARY ANSWER: We imputed identity-by-state (IBS) sharing of parental siblings to phase parental genotypes. WHAT IS KNOWN ALREADY: Genome-wide haplotyping of preimplantation embryos is being implemented as a generic approach for genetic diagnosis of inherited single-gene disorders. To enable the phasing of genotypes into haplotypes, genotyping the direct family members of the prospective parent carrying the mutation is required. Current approaches require genotypes of either (i) both or one of the parents of the affected prospective parent or (ii) an affected or an unaffected child of the couple. However, this approach cannot be used when parents or children are not attainable, prompting an investigation into alternative phasing options. STUDY DESIGN, SIZE, DURATION: This is a retrospective validation study, which applied IBS-based phasing of parental haplotypes in 56 embryos derived from 12 PGT families. Genome-wide haplotypes and copy number profiles generated for each embryo using the new phasing approach were compared with the reference PGT method to evaluate the diagnostic concordance. PARTICIPANTS/MATERIALS, SETTING, METHODS: This study included 12 couples with a known hereditary genetic disorder, participating in the comprehensive PGT program and with at least one parental sibling available (e.g. brother and/or sister). Genotyping data from both prospective parents and the parental sibling(s) were used to perform IBS-based phasing and to trace the disease-associated alleles. The outcome of the IBS-based PGT was compared with the results of the clinically implemented reference haplotyping-based PGT method. MAIN RESULTS AND THE ROLE OF CHANCE: IBS-based haplotyping was performed for 12 PGT families. In accordance with the theoretical prediction of allele sharing between sibling pairs, 6 out of 12 (50%) couples or 23 out of 56 embryos could be phased using parental siblings. In families where phasing was possible, haplotype calling in the locus of interest was 100% concordant between the reference PGT method and IBS-based approach using parental siblings. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Phasing of parental haplotypes will only be possible when the disease locus lies in an informative region (categorized as IBS1). Phasing prospective parents using relatives with reduced genetic relatedness as a reference (e.g. siblings) decreases the size and the occurrence of informative IBS1 regions, necessary for haplotype calling. By including more than one extended family member, the chance of obtaining IBS1 coverage in the interrogated locus can be increased. A pre-PGT work-up can define whether the carrier couple could benefit from this approach. WIDER IMPLICATIONS OF THE FINDINGS: Phasing by relatives extends the potential of comprehensive PGT, since it allows the inclusion of couples who do not have access to the standard phasing references, such as parents or offspring. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by the KU Leuven grant (C14/18/092), Research Foundation Flanders (FWO; GA09311N), Horizon 2020 innovation programme (WIDENLIFE, 692065) and Agilent Technologies. J.R.V., T.V. and M.Z.E. are co-inventors of a patent ZL910050-PCT/EP2011/060211-WO/2011/157846 'Methods for haplotyping single-cells' and ZL913096-PCT/EP2014/068315-WO/2015/028576 'Haplotyping and copy number typing using polymorphic variant allelic frequencies' licensed to Agilent Technologies. The other authors have no conflict of interest to declare.

4.
Genet Med ; 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-32024963

RESUMO

PURPOSE: Whereas noninvasive prenatal screening for aneuploidies is widely implemented, there is an increasing need for universal approaches for noninvasive prenatal screening for monogenic diseases. Here, we present a cost-effective, generic cell-free fetal DNA (cffDNA) haplotyping approach to scan the fetal genome for the presence of inherited monogenic diseases. METHODS: Families participating in the preimplantation genetic testing for monogenic disorders (PGT-M) program were recruited for this study. Two hundred fifty thousand single-nucleotide polymorphisms (SNPs) captured from maternal plasma DNA along with genomic DNA from family members were massively parallel sequenced. Parental genotypes were phased via an available genotype from a close relative, and the fetal genome-wide haplotype and copy number were determined using cffDNA haplotyping analysis based on estimation and segmentation of fetal allele presence in the maternal plasma. RESULTS: In all families tested, mutational profiles from cffDNA haplotyping are consistent with embryo biopsy profiles. Genome-wide fetal haplotypes are on average 97% concordant with the newborn haplotypes and embryo haplotypes. CONCLUSION: We demonstrate that genome-wide targeted capture and sequencing of polymorphic SNPs from maternal plasma cell-free DNA (cfDNA) allows haplotyping and copy-number profiling of the fetal genome during pregnancy. The method enables the accurate reconstruction of the fetal haplotypes and can be easily implemented in clinical practice.

5.
Mol Psychiatry ; 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-32015465

RESUMO

Schizophrenia occurs in about one in four individuals with 22q11.2 deletion syndrome (22q11.2DS). The aim of this International Brain and Behavior 22q11.2DS Consortium (IBBC) study was to identify genetic factors that contribute to schizophrenia, in addition to the ~20-fold increased risk conveyed by the 22q11.2 deletion. Using whole-genome sequencing data from 519 unrelated individuals with 22q11.2DS, we conducted genome-wide comparisons of common and rare variants between those with schizophrenia and those with no psychotic disorder at age ≥25 years. Available microarray data enabled direct comparison of polygenic risk for schizophrenia between 22q11.2DS and independent population samples with no 22q11.2 deletion, with and without schizophrenia (total n = 35,182). Polygenic risk for schizophrenia within 22q11.2DS was significantly greater for those with schizophrenia (padj = 6.73 × 10-6). Novel reciprocal case-control comparisons between the 22q11.2DS and population-based cohorts showed that polygenic risk score was significantly greater in individuals with psychotic illness, regardless of the presence of the 22q11.2 deletion. Within the 22q11.2DS cohort, results of gene-set analyses showed some support for rare variants affecting synaptic genes. No common or rare variants within the 22q11.2 deletion region were significantly associated with schizophrenia. These findings suggest that in addition to the deletion conferring a greatly increased risk to schizophrenia, the risk is higher when the 22q11.2 deletion and common polygenic risk factors that contribute to schizophrenia in the general population are both present.

6.
Clin Genet ; 97(4): 595-600, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32022899

RESUMO

Ectodermal dysplasias are a family of genodermatoses commonly associated with variants in the ectodysplasin/NF-κB or the Wnt/ß-catenin pathways. Both pathways are involved in signal transduction from ectoderm to mesenchyme during the development of ectoderm-derived structures. Wnt/ß-catenin pathway requires the lymphoid enhancer-binding factor 1 (LEF1), a nuclear mediator, to activate target gene expression. In mice, targeted inactivation of the LEF1 gene results in a complete block of development of multiple ectodermal appendages. We report two unrelated patients with 4q25 de novo deletion encompassing LEF1, associated with severe oligodontia of primary and permanent dentition, hypotrichosis and hypohidrosis compatible with hypohidrotic ectodermal dysplasia. Taurodontism and a particular alveolar bone defect were also observed in both patients. So far, no pathogenic variants or variations involving the LEF1 gene have been reported in human. We provide further evidence for LEF1 haploinsufficiency role in ectodermal dysplasia and delineate its clinical phenotype.

7.
J Med Genet ; 2020 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-31932357

RESUMO

BACKGROUND: Intragenic NRXN1 deletions are susceptibility variants for neurodevelopmental disorders; however, their clinical interpretation is often unclear. Therefore, a literature study and an analysis of 43 previously unpublished deletions are provided. METHODS: The literature cohort covered 629 heterozygous NRXN1 deletions: 148 in controls, 341 in probands and 140 in carrier relatives, and was used for clinical hypothesis testing. Exact breakpoint determination was performed for 43 in-house deletions. RESULTS: The prevalence of exonic NRXN1 deletions in controls was ~1/3000 as compared with ~1/800 in patients with neurodevelopmental/neuropsychiatric disorders. The differential distribution of deletions across the gene between controls and probands allowed to distinguish distinct areas within the gene. Exon 6-24 deletions appeared only twice in over 100000 control individuals, had an estimated penetrance for neurodevelopmental disorders of 32.43%, a de novo rate of 50% and segregated mainly with intellectual disability (ID) and schizophrenia. In contrast, exon 1-5 deletions appeared in 20 control individuals, had an estimated penetrance of 12.59%, a de novo rate of 32.5% and were reported with a broad range of neurodevelopmental phenotypes. Exact breakpoint determination revealed six recurrent intron 5 deletions. CONCLUSION: Exon 6-24 deletions have a high penetrance and are mainly associated with ID and schizophrenia. In contrast, the actual contribution of exon 1-5 deletions to a neurodevelopmental/neuropsychiatric disorder in an individual patient and family remains very difficult to assess. To enhance the clinical interpretation, this study provides practical considerations for counselling and an interactive table for comparing a deletion of interest with the available literature data.

8.
Acta Clin Belg ; 75(1): 9-18, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31578135

RESUMO

Background: The last half-decade has been marked by a rapid expansion of research efforts in the field of so-called liquid biopsies, thereby investigating the potential of blood-derived cell-free tumour DNA (ctDNA) markers for application in clinical oncological management. The analysis of cfDNA appears to be particularly attractive for therapy monitoring purposes, while in terms of early cancer diagnosis and screening the potentials are just starting to be explored. Challenges, both of biological and technical nature, need to be addressed. One such challenge is to overcome the low levels of ctDNA in the circulation, intrinsic to many early-stage cancers. Methods: Here, we give an overview of the features of ctDNA and the approaches that are currently being applied with the ultimate aim to detect tumours in a presymptomatic stage. Conclusion: Although many studies report encouraging results, further technical development and larger studies are warranted before application of ctDNA analysis may find its place in clinic.

9.
Genet Med ; 22(2): 326-335, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31474763

RESUMO

PURPOSE: The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion in humans, with highly variable phenotypic expression. Whereas congenital heart defects, palatal anomalies, immunodeficiency, hypoparathyroidism, and neuropsychiatric conditions are observed in over 50% of patients with 22q11DS, a subset of patients present with additional "atypical" findings such as craniosynostosis and anorectal malformations. Recently, pathogenic variants in the CDC45 (Cell Division Cycle protein 45) gene, located within the LCR22A-LCR22B region of chromosome 22q11.2, were noted to be involved in the pathogenesis of craniosynostosis. METHODS: We performed next-generation sequencing on DNA from 15 patients with 22q11.2DS and atypical phenotypic features such as craniosynostosis, short stature, skeletal differences, and anorectal malformations. RESULTS: We identified four novel rare nonsynonymous variants in CDC45 in 5/15 patients with 22q11.2DS and craniosynostosis and/or other atypical findings. CONCLUSION: This study supports CDC45 as a causative gene in craniosynostosis, as well as a number of other anomalies. We suggest that this association results in a condition independent of Meier-Gorlin syndrome, perhaps representing a novel condition and/or a cause of features associated with Baller-Gerold syndrome. In addition, this work confirms that the phenotypic variability observed in a subset of patients with 22q11.2DS is due to pathogenic variants on the nondeleted chromosome.

10.
Am J Hum Genet ; 106(1): 26-40, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31870554

RESUMO

The 22q11.2 deletion syndrome (22q11.2DS) results from non-allelic homologous recombination between low-copy repeats termed LCR22. About 60%-70% of individuals with the typical 3 megabase (Mb) deletion from LCR22A-D have congenital heart disease, mostly of the conotruncal type (CTD), whereas others have normal cardiac anatomy. In this study, we tested whether variants in the hemizygous LCR22A-D region are associated with risk for CTDs on the basis of the sequence of the 22q11.2 region from 1,053 22q11.2DS individuals. We found a significant association (FDR p < 0.05) of the CTD subset with 62 common variants in a single linkage disequilibrium (LD) block in a 350 kb interval harboring CRKL. A total of 45 of the 62 variants were associated with increased risk for CTDs (odds ratio [OR) ranges: 1.64-4.75). Associations of four variants were replicated in a meta-analysis of three genome-wide association studies of CTDs in affected individuals without 22q11.2DS. One of the replicated variants, rs178252, is located in an open chromatin region and resides in the double-elite enhancer, GH22J020947, that is predicted to regulate CRKL (CRK-like proto-oncogene, cytoplasmic adaptor) expression. Approximately 23% of patients with nested LCR22C-D deletions have CTDs, and inactivation of Crkl in mice causes CTDs, thus implicating this gene as a modifier. Rs178252 and rs6004160 are expression quantitative trait loci (eQTLs) of CRKL. Furthermore, set-based tests identified an enhancer that is predicted to target CRKL and is significantly associated with CTD risk (GH22J020946, sequence kernal association test (SKAT) p = 7.21 × 10-5) in the 22q11.2DS cohort. These findings suggest that variance in CTD penetrance in the 22q11.2DS population can be explained in part by variants affecting CRKL expression.

11.
Genes (Basel) ; 10(12)2019 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-31817908

RESUMO

Non-syndromic cleft lip with or without cleft palate (nsCL/P) ranks among the most common human congenital malformations, and has a multifactorial background in which both exogenous and genetic risk factors act in concert. The present report describes a genome-wide association study (GWAS) involving a total of 285 nsCL/P patients and 1212 controls from the Netherlands and Belgium. Twenty of the 40 previously reported nsC/LP susceptibility loci were replicated, which underlined the validity of this sample. SNV-based analysis of the data identified an as yet unreported suggestive locus at chromosome 16p12.1 (p-value of the lead SNV: 4.17 × 10-7). This association was replicated in two of three patient/control replication series (Central European and Yemeni). Gene analysis of the GWAS data prioritized SH3PXD2A at chromosome 10q24.33 as a candidate gene for nsCL/P. To date, support for this gene as a cleft gene has been restricted to data from zebrafish and a knockout mouse model. The present GWAS was the first to implicate SH3PXD2A in non-syndromic cleft formation in humans. In summary, although performed in a relatively small sample, the present GWAS generated novel insights into nsCL/P etiology.

12.
Hum Mol Genet ; 28(22): 3724-3733, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31884517

RESUMO

The majority (99%) of individuals with 22q11.2 deletion syndrome (22q11.2DS) have a deletion that is caused by non-allelic homologous recombination between two of four low copy repeat clusters on chromosome 22q11.2 (LCR22s). However, in a small subset of patients, atypical deletions are observed with at least one deletion breakpoint within unique sequence between the LCR22s. The position of the chromosome breakpoints and the mechanisms driving those atypical deletions remain poorly studied. Our large-scale, whole genome sequencing study of >1500 subjects with 22q11.2DS identified six unrelated individuals with atypical deletions of different types. Using a combination of whole genome sequencing data and fiber-fluorescence in situ hybridization, we mapped the rearranged alleles in these subjects. In four of them, the distal breakpoints mapped within one of the LCR22s and we found that the deletions likely occurred by replication-based mechanisms. Interestingly, in two of them, an inversion probably preceded inter-chromosomal 'allelic' homologous recombination between differently oriented LCR22-D alleles. Inversion associated allelic homologous recombination (AHR) may well be a common mechanism driving (atypical) deletions on 22q11.2.

13.
Prenat Diagn ; 39(13): 1262-1268, 2019 12.
Artigo em Alemão | MEDLINE | ID: mdl-31691324

RESUMO

OBJECTIVE: The study aimed to validate a whole-genome sequencing-based NIPT laboratory method and our recently developed NIPTmer aneuploidy detection software with the potential to integrate the pipeline into prenatal clinical care in Estonia. METHOD: In total, 424 maternal blood samples were included. Analysis pipeline involved cell-free DNA extraction, library preparation and massively parallel sequencing on Illumina platform. Aneuploidies were determined with NIPTmer software, which is based on counting pre-defined per-chromosome sets of unique k-mers from sequencing raw data. SeqFF was implemented to estimate cell-free fetal DNA (cffDNA) fraction. RESULTS: NIPTmer identified correctly all samples of non-mosaic trisomy 21 (T21, 15/15), T18 (9/9), T13 (4/4) and monosomy X (4/4) cases, with the 100% sensitivity. However, one mosaic T18 remained undetected. Six false-positive (FP) results were observed (FP rate of 1.5%, 6/398), including three for T18 (specificity 99.3%) and three for T13 (specificity 99.3%). The level of cffDNA of <4% was estimated in eight samples, including one sample with T13 and T18. Despite low cffDNA level, these two samples were determined as aneuploid. CONCLUSION: We believe that the developed NIPT method can successfully be used as a universal primary screening test in combination with ultrasound scan for the first trimester fetal examination.

14.
Nat Med ; 25(11): 1699-1705, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31686035

RESUMO

Although chromosomal instability (CIN) is a common phenomenon in cleavage-stage embryogenesis following in vitro fertilization (IVF)1-3, its rate in naturally conceived human embryos is unknown. CIN leads to mosaic embryos that contain a combination of genetically normal and abnormal cells, and is significantly higher in in vitro-produced preimplantation embryos as compared to in vivo-conceived preimplantation embryos4. Even though embryos with CIN-derived complex aneuploidies may arrest between the cleavage and blastocyst stages of embryogenesis5,6, a high number of embryos containing abnormal cells can pass this strong selection barrier7,8. However, neither the prevalence nor extent of CIN during prenatal development and at birth, following IVF treatment, is well understood. Here we profiled the genomic landscape of fetal and placental tissues postpartum from both IVF and naturally conceived children, to investigate the prevalence and persistence of large genetic aberrations that probably arose from IVF-related CIN. We demonstrate that CIN is not preserved at later stages of prenatal development, and that de novo numerical aberrations or large structural DNA imbalances occur at similar rates in IVF and naturally conceived live-born neonates. Our findings affirm that human IVF treatment has no detrimental effect on the chromosomal constitution of fetal and placental lineages.


Assuntos
Instabilidade Cromossômica/genética , Variações do Número de Cópias de DNA/genética , Desenvolvimento Embrionário/genética , Fertilização In Vitro/efeitos adversos , Blastocisto/metabolismo , Linhagem da Célula/genética , Embrião de Mamíferos , Feminino , Feto , Genótipo , Humanos , Recém-Nascido , Masculino , Placenta/metabolismo , Placenta/patologia , Polimorfismo de Nucleotídeo Único/genética , Gravidez
16.
Hum Mutat ; 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31646703

RESUMO

We recently described a new neurodevelopmental syndrome (TAF1/MRXS33 intellectual disability syndrome) (MIM# 300966) caused by pathogenic variants involving the X-linked gene TAF1, which participates in RNA polymerase II transcription. The initial study reported eleven families, and the syndrome was defined as presenting early in life with hypotonia, facial dysmorphia, and developmental delay that evolved into intellectual disability (ID) and/or autism spectrum disorder (ASD). We have now identified an additional 27 families through a genotype-first approach. Familial segregation analysis, clinical phenotyping, and bioinformatics were capitalized on to assess potential variant pathogenicity, and molecular modelling was performed for those variants falling within structurally characterized domains of TAF1. A novel phenotypic clustering approach was also applied, in which the phenotypes of affected individuals were classified using 51 standardized Human Phenotype Ontology (HPO) terms. Phenotypes associated with TAF1 variants show considerable pleiotropy and clinical variability, but prominent among previously unreported effects were brain morphological abnormalities, seizures, hearing loss, and heart malformations. Our allelic series broadens the phenotypic spectrum of TAF1/MRXS33 intellectual disability syndrome and the range of TAF1 molecular defects in humans. It also illustrates the challenges for determining the pathogenicity of inherited missense variants, particularly for genes mapping to chromosome X. This article is protected by copyright. All rights reserved.

18.
Genome Res ; 29(9): 1389-1401, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31481461

RESUMO

Low copy repeats (LCRs) are recognized as a significant source of genomic instability, driving genome variability and evolution. The Chromosome 22 LCRs (LCR22s) mediate nonallelic homologous recombination (NAHR) leading to the 22q11 deletion syndrome (22q11DS). However, LCR22s are among the most complex regions in the genome, and their structure remains unresolved. The difficulty in generating accurate maps of LCR22s has also hindered localization of the deletion end points in 22q11DS patients. Using fiber FISH and Bionano optical mapping, we assembled LCR22 alleles in 187 cell lines. Our analysis uncovered an unprecedented level of variation in LCR22s, including LCR22A alleles ranging in size from 250 to 2000 kb. Further, the incidence of various LCR22 alleles varied within different populations. Additionally, the analysis of LCR22s in 22q11DS patients and their parents enabled further refinement of the rearrangement site within LCR22A and -D, which flank the 22q11 deletion. The NAHR site was localized to a 160-kb paralog shared between the LCR22A and -D in seven 22q11DS patients. Thus, we present the most comprehensive map of LCR22 variation to date. This will greatly facilitate the investigation of the role of LCR variation as a driver of 22q11 rearrangements and the phenotypic variability among 22q11DS patients.


Assuntos
Síndrome da Deleção 22q11/genética , Mapeamento Cromossômico/métodos , Cromossomos Humanos Par 22/genética , Sequências Repetitivas de Ácido Nucleico , Animais , Linhagem Celular , Instabilidade Cromossômica , Evolução Molecular , Humanos , Hibridização in Situ Fluorescente , Primatas/genética
20.
NPJ Genom Med ; 4: 15, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31285848

RESUMO

Non-invasive prenatal testing (NIPT) is accurate for fetal sex determination in singleton pregnancies, but its accuracy is not well established in twin pregnancies. Here, we present an accurate sex prediction model to discriminate fetal sex in both dichorionic diamniotic (DCDA) and monochorionic diamniotic/monochorionic monoamniotic (MCDA/MCMA) twin pregnancies. A retrospective analysis was performed using a total of 198 twin pregnancies with documented sex. The prediction was based on a multinomial logistic regression using the normalized frequency of X and Y chromosomes, and fetal fraction estimation. A second-step regression analysis was applied when one or both twins were predicted to be male. The model determines fetal sex with 100% sensitivity and specificity when both twins are female, and with 98% sensitivity and 95% specificity when a male is present. Since sex determination can be clinically important, implementing fetal sex determination in twins will improve overall twin pregnancies management.

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