Fetal Chromosome Research Articles

Specific Short Tandem Repeat Loci Detection in Prenatal Diagnosis of Fetal Chromosomal Diseases.

It was to investigate the value of quantitative fluorescence PCR (QF-PCR) for the selection of specific short tandem repeat (STR) in prenatal diagnosis of fetal chromosomal diseases. Amniotic fluid (AF) and villus samples were obtained from 80 pregnant women at 16-20 weeks of gestation, and venous blood samples were obtained from 60 normal individuals to extract and prepare peripheral blood chromosome, AF cell chromosome, and villus cell chromosome samples for specific STR locus detection. It showed that the area ratio of AMX peak to AMY peak in the Genescan typing map of peripheral blood DNA of normal males was close to 1:1, while the Genescan typing map of peripheral blood DNA of normal females had only AMX peak and no AMY peak. Normal heterozygous individuals had an area ratio between 1 and 1.45 for venous blood, 1.002 and 1.27 for villous samples, and 1 and 1.35 for AF samples. The karyotype of a male fetus was 46, XY, inv [9] (p11: q13), and the structure of fetal chromosome 9 was inverted (interarm), and the site of structural inversion was band 1 in the short breech 1 region and band 3 in the long arm 1 region of chromosome 9. It suggested that QF-PCR can effectively identify the normal human body and cases by selecting specific STR locus detection, which has a good application value for prenatal diagnosis of fetal chromosomal diseases.

NanoNIPT: Short-fragment nanopore sequencing of cell-free DNA for non-invasive prenatal testing of fetal aneuploidies and sex chromosome aberrations.

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Analysis of a fetus with unbalanced translocation derived from a balanced t(6;14) maternal translocation

To explore the genetic characteristics of a fetus with a high risk by maternal serum screening during the second trimester. Genetic counseling was provided to the pregnant woman on March 22, 2020 at Henan Provincial People's Hospital. G-banded chromosomal karyotyping and array comparative genomic hybridization (aCGH) were carried out on the amniotic fluid sample and peripheral blood samples from the couple. The fetus and the pregnant woman were respectively found to have a 46,XX,der(6)t(6;14)(q27;q31.2) and 46,XX,t(6;14)(q27;q31.2) karyotype, whilst the husband was found to have a normal karyotype. aCGH analysis has identified a 6.64 Mb deletion at 6q26q27 and a 19.98 Mb duplication at 14q31.3q32.33 in the fetus, both of which were predicted to be pathogenic copy number variations. No copy number variation was found in the couple. The unbalanced chromosome abnormalities in the fetus have probably derived from the balanced translocation carried by the pregnant woman. aCGH can help to determine the types of fetal chromosome abnormalities and site of chromosomal breakage, which may facilitate the prediction of fetal outcome and choice for subsequent pregnancies.

Inclusion of sex chromosomes in noninvasive prenatal testing in Asia, Australia, Europe and the USA: A survey study.

To examine the extent to which sex chromosomes are included in current noninvasive prenatal testing (NIPT) and the reporting practices with respect to fetal chromosomal sex and sex chromosome aberrations (SCAs), in addition to an update on the general implementation of NIPT. A questionnaire addressing the research objectives was distributed by email to fetal medicine and clinical genetics experts in Asia, Australia, Europe and the USA. Guidelines on NIPT are available in the majority of the included countries. Not all existing guidelines address reporting of fetal chromosomal sex and SCAs. In most settings, NIPT frequently includes sex chromosomes (five Australian states, China, Hong Kong, Israel, Singapore, Thailand, USA and 23 of 31 European countries). This occurs most often by default or when parents wish to know fetal sex. In most settings, a potential SCA is reported by stating the risk hereof as "low" or "high" and/or by naming the SCA. Less than 50% of all pregnant women receive NIPT according to respondents from three Australian states, China, Israel, Singapore, Thailand and 24 of 31 European countries. However, this percentage, the genomic coverage of NIPT and its application as primary or secondary screening vary by setting. In most of the studied countries/states, NIPT commonly includes sex chromosomes. The reporting practices concerning fetal chromosomal sex and SCAs are diverse and most commonly not addressed by guidelines. In general, NIPT is variably implemented across countries/states.

A systematic review and meta-analysis of cell-free DNA testing for detection of fetal sex chromosome aneuploidy.

The aim was to determine the accuracy of cell-free DNA testing (cfDNA) for detecting sex chromosome aneuploidies (SCA) in singleton pregnancies. A systematic review and meta-analysis was performed to assess cfDNA accuracy for prenatal detection of 45,X, 47,XXY, 47,XXX and 47,XYY. Inclusion was restricted to studies published between January 2010 and December 2021 reporting both cfDNA and confirmatory diagnostic test results. For 45,X, the sensitivity was 98.8% (95%CI 94.6%-100%), specificity 99.4% (95%CI 98.7%-99.9%) and positive predictive value (PPV) 14.5% (95%CI 7.0%-43.8%). For 47,XXY, the sensitivity was 100% (95%CI 99.6%-100%), specificity 100% (95%CI 99.9%-100%) and PPV 97.7% (95%CI 78.6%-100%). For 47,XXX, the sensitivity was 100% (95%CI 96.9%-100%), specificity 99.9% (95%CI 99.7%-100%) and PPV 61.6% (95%CI 37.6%-95.4%). For 47,XYY, the sensitivity was 100% (95%CI 91.3%-100%), specificity 100% (95% CI 100%-100%) and PPV 100% (95%CI 76.5%-100%). All four SCAs had estimated negative predictive values (NPV) exceeding 99.99%, though false negatives were reported. This analysis suggests that cfDNA is a reliable screening test for SCA, though both false negatives and false positives were reported. These estimates of test performance are derived from pregnancies at high pretest risk for aneuploidy, limiting the generalisability to average risk pregnancies.

The Clinical Application and Accuracy Evaluation of Noninvasive Prenatal Testing for Common Trisomy and Sex Chromosome Aneuploidy.

Noninvasive prenatal testing (NIPT) has been widely adopted in prenatal examination for fetal chromosomal aneuploidy. The present study aimed to evaluate the clinical features of NIPT for both common trisomy and sex chromosome aneuploidy (SCA). A total of 24,164 pregnant women with NIPT testing from July 2020 to June 2022 were recruited at the Linping Maternity and Child Health Care Hospital. Ninety cases showed high risk of trisomy 21/18/13 with karyotype results available, and the sensitivity, specificity, and positive predictive value (PPV) were 98.41%, 99.88% and 68.89%, respectively. The three most important reasons for screening were advanced maternal age (AMA, 28.06%), intermediate risk of prenatal screening (20.34%) and Multiple of medium (MoM) abnormality of prenatal screening (17.38%). High risk of NIPT results with Z-score ≥15 have a higher PPV when compared to those with 3 ≤ Z-score < 10, and 10 ≤ Z-score < 15. Meanwhile, 97 pregnant women received positive results for fetal sex chromosome aneuploidy (SCA) in NIPT. In addition, the rate for further diagnostics of SCA was 64.95% and the PPV of SCA was 50.79%. Our data show that NIPT has a promising future in prenatal screening for genetic abnormalities of the fetus, and that the accuracy of NIPT is closely related to Z-score.

The role of non-invasive prenatal testing and ultrasound in prenatal screening of fetal chromosomal abnormalities in singleton: a retrospective study.

Non-invasive prenatal testing (NIPT) has good screening performance for common chromosomes, but it may have false positive (FP) and false negative (FN) results for various reasons. For abnormal NIPT results, the combination of fetal ultrasound phenotypes will provide more fetal information for prenatal diagnosis. The aim of this study was to combine NIPT and ultrasound phenotypes to analyze their complementary roles in prenatal screening of fetal chromosome abnormalities. From January 2018 to December 2021, 12,803 pregnant women with singleton who successfully underwent NIPT/expanded NIPT (NIPT-Plus) at Xiangya Hospital of Central South University, of which 111 cases were positive results and one case was FN result. We retrospectively collected the clinical features, ultrasonographic findings, prenatal diagnosis, and pregnancy outcomes of these 112 pregnant women and analyzed the ultrasonic manifestations of different chromosomal abnormalities in detail. The positive predictive values (PPVs) of NIPT/NIPT-Plus for trisomy (T)21, T18, sex chromosome abnormality (SCA), microdeletion/microduplication syndrome (MMS), T13, and rare autosomal trisomy (RAT) were 100.0%, 85.7%, 57.1%, 44.4%, 40.0%, and 7.7%, respectively. The total termination rates of pregnancy for T21, T18, T13, SCA, pathogenic MMS, and RAT were 93.5%, 100.0%, 100.0%, 66.7%, 100.0%, and 100.0%, respectively. From the karyotypes of SCA live-born fetuses, 47,XYY and 47,XXX were more likely to be selected for continued pregnancy. The ultrasound phenotypes of T21 were diverse, including normal, soft marker, and structural malformation. Both T18 and T13 had structural malformations as the main phenotypes. Most ultrasound phenotypes of FP T21, T18, and T13 were normal but occasionally manifested as fetal growth restriction (FGR). The ultrasound phenotypes of SCA, MMS, and RAT were relatively mild and manifested as normal, soft marker, FGR, or polyhydramnios, and the ultrasound phenotypes were similar between FP and true positive (TP) cases. Ultrasound phenotypes are helpful in identifying FP NIPT/NIPT-Plus results, especially for T18 and T13. Given its mild ultrasound phenotypes, NIPT-Plus has important clinical significance in reducing the missed diagnosis of SCA, MMS, and RAT, but its screening performance needs to be further improved.

Cell-free DNA versus sequential screening for fetal chromosomal abnormalities varied by age: a cost-effectiveness analysis

Cell-free DNA (cfDNA) and sequential screening (SS) are frequently used for prenatal genetic screening. Though cfDNA has higher detection rates for common aneuploidies, SS may better identify risk for other nontargeted aneuploidies. We compared the cost-effectiveness of cfDNA versus SS for detection of fetal chromosome abnormalities across varied age cohorts. A decision-analytic model compared cfDNA versus SS for diagnosis of chromosomal abnormalities across different maternal age cohorts stratified by 5-year increments of < 20, 20-24, 25-29, 30-34, 35-39, 40-44, and >45 years. Chromosomal abnormalities included trisomy 21 (T21), trisomy 18 (T18), trisomy 13 (T13), 45X syndrome, sex chromosome abnormalities (SCA), and other nontargeted chromosomal abnormalities . Probabilities, costs, and utilities were derived from literature and varied in sensitivity analysis. The primary outcome was incremental cost per quality-adjusted life year (QALY). We also considered affected neonates, missed prenatal diagnoses, procedure-related loss (PRL), pregnancy termination (TOP), stillbirth, and neonatal death (NND). The cost-effectiveness threshold was $100,000/QALY. SS was cost-effective for detection of all fetal chromosome abnormalities until age 39. Cell-free DNA was only cost-effective starting at age 40, with an Incremental Cost Effectiveness Ratio (ICER) of $51,919/QALY (40-44 years) and ICER $16,830/QALY ( >44 years). In all maternal age cohorts, cfDNA led to more frequent identification of T21, T18, T13, 45X and SCA but fewer other nontargeted chromosomal abnormalities. cfDNA was associated with more terminations and fewer stillbirths, NND, and PRL. The model was sensitive to the prevalence of T21. When varying the prevalence of T21 in the age 35-39 cohort cfDNA was cost effective when the prevalence of T21 was greater than 0.017 which corresponds with the prevalence of T21 at a maternal age of 39. Compared to cfDNA, SS is a cost-effective screening method for fetal chromosome abnormalities for pregnant persons under the age of 40 at a population-based level.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Retrospective analysis for 424 330 first-line screening results of non-invasive prenatal testing in Hebei province

Objective: To evaluate the effect of noninvasive prenatal testing (NIPT) as first-line screening in fetal chromosome aneuploidy screening practice, and to provide evidence for the prevention and control strategy of birth defects. Methods: Since July 2019, Hebei province had carried out the NIPT project providing first-line screening for eligible pregnant women in the area (except for those who were not applicable). Pregnant women with high risk received genetic counseling, prenatal diagnosis and intervention guidance. Low risk and false-positive ones received continuous detection and moved to prenatal diagnosis center for counseling and diagnosis if abnormities were discovered. All pregnant women were followed up to learn about pregnancy outcomes and newborn health status. Detection results and clinical data of pregnant women participating the NIPT project from July 2019 to July 2020 were collected. The detection results and effect of NIPT were analyzed. Results: (1) Basic information of the screened population: A total of 424 330 pregnant women were screened, and 423 596 were successfully detected, with a success rate of 99.83% (423 596/424 330). The age of pregnant women was (28.8±4.5) years old; the gestational age of screening was (16.6±2.3) weeks; the proportion of advanced-age pregnant women (≥35 years old) was 10.18% (43 132/423 596); in vitro fertilization-embryo transfer (IVF-ET) rate was 1.58% (6 713/423 596); the twin rate was 1.38% (5 849/423 596); the proportion of primipara was 34.23% (144 977/423 596). (2) Screening results and detection performance: totally, 325, 73 and 20 pregnant women were diagnosed with trisomy 21, 18 and 13; the sensitivity were 99.39%, 100.00% and 100.00%; the specificity were 99.98%, 99.99% and 99.98%; the positive predictive value were 75.76%, 68.87% and 21.51%, respectively. Besides, 249 190 pregnant women were received supplementary reports as well, and 255, 10 and 9 were confirmed for sex chromosome aneuploidy, other autosomal aneuploidy and deletion/duplication syndrome; the positive predictive value were 37.78%, 6.06% and 32.14%, respectively. The sensitivity of NIPT for target trisomy (trisomy 21, 18 and 13) screening in advanced-age, IVF-ET and twin pregnant women were 99.29%, 100.00% and 90.00%, respectively; the specificity were 99.93% for all; the positive predictive value were 82.25%, 61.54% and 69.23%, respectively. Conclusions: NIPT has a significant effect and good performance in the first-line screening of fetal chromosome aneuploidy in the whole population, which might provide reference for the improvement of birth defect prevention and control strategy.

Inconsistency between non-invasive prenatal testing (NIPT) and conventional prenatal diagnosis due to confined placental and fetal mosaicism: Two case reports.

We aimed to identify the causes of inconsistent results between non-invasive prenatal testing (NIPT) and invasive testing methods for trisomy 21. In the first case, NIPT was performed at 11 weeks of pregnancy, and the result showed a high risk of trisomy 21 [fetal fraction (FF) = 6.98%, 21 chromosome Z-score = 3.6]. The patient underwent quantitative fluorescent (QF)-PCR and karyotyping at 14 + 0 weeks of pregnancy through CVS showing mosaicism of 47, XX, + 21[11] and 46, XX [39] in karyotyping. The patient underwent amniocentesis at 15 + 6 weeks, showing a normal pattern in QF-PCR and 46, XX karyotyping in long term culture. The second case underwent NIPT at 16 + 5 weeks of pregnancy (FF = 7.52%, 21 chromosome Z-score = 2.503). She underwent an invasive test at 19 weeks through amniotic fluid sampling. As a result, trisomy 21 was detected by QF-PCR, and mosaicism of XX, +21[22]/46, XX [4] was identified by karyotyping. Despite significant advances in fetal chromosome analysis using NIPT, invasive testing is still needed as placenta-derived DNA does not reflect 100% fetal genetic information. Placental mosaicism can be detected by NIPT, but more research is needed to increase its sensitivity. Therefore, if the NIPT result is positive, an invasive test can confirm the result, and continuous monitoring is required even if the NIPT result is negative.

Residual risk of noninvasive prenatal screening in pregnancies with ultrasound anomalies

ObjectivesTo discuss the residual risk (RR) of noninvasive prenatal screening (NIPS) for the mothers with fetal ultrasound abnormalities. Methods880 pregnant women with fetal ultrasound abnormalities accepted prenatal diagnosis by chromosomal microarray analysis (CMA) after amniocentesis. Furthermore, the detection efficiency of NIPS was evaluated and calculated based on our previous studies and other literatures. The RR of the chromosome abnormality results was then analyzed. ResultsA total of 103 cases were confirmed as fetal chromosome abnormalities, including 65 (63.1%) of aneuploidies and 38 (36.9%) of clinical significant copy number variations (CNVs). Of which, based on the estimated NIPS efficacy, 87 cases could also be detected by NIPS. The detection rate (DR) was 84.5%, while 16 cases would be missed. The total of RR of NIPS in the fetuses with ultrasound anomalies was 2.0% (16/793), approximately one in 51. The top three RR of fetal ultrasound abnormalities were echogenic bowel (5.9%), multiple systems of structural anomalies (4.5%), and nervous system anomalies (4.2%). ConclusionThe overall residual risk of NIPS in the fetuses with ultrasound anomalies was approximately 2.0%, especially in echogenic bowel, multiple systems of structural anomalies and nervous system anomalies.

Cell-Free Fetal Deoxyribonucleic Acid (cffDNA) Analysis as a Remarkable Method of Non-Invasive Prenatal Screening

The cell-free fetal DNA (cffDNA) analysis for screening fetal genetic anomalies has increased dramatically since its commercialization in 2011 worldwide. In the early weeks of pregnancy, it offers a hassle-free, non-invasive procedure of antenatal screening. It guides and protects mothers from undergoing unwanted risk-laden invasive prenatal testing. cffDNA testing is accurate at detecting the abnormal fetus chromosome among a large pool population. Patau syndrome, Edward syndrome, and Down syndrome are currently being accurately screened by this method. Due to their sensitivity and specificity, they now have become the screening method of choice, approaching almost 100% in various studies with a large sample pool. The latest procedures to analyze cffDNA, like the new digital droplet polymerase chain reaction (ddPCR) and sophisticated next-generation sequencing (NGS), haveincreased detection rates with decreased analyzing time. The latest techniques make it possible to screen large numbers of the population with faster report generation. Screening for Rh incompatibility and its timely prevention is now more accessible and more accurate with the help of cffDNA analysis. The problem arises when we deviate from the primary disease and start testing for anomalies not intended to be screened by cffDNA in the first place. Fetal sex chromosome aneuploidy screening by cffDNA is one area where the test gives mixed results either due to differences in machinery, laboratory parameters, or human error. Other rare occurrences like trisomes, such as trisomy 7, trisomy 16, trisomy 22, and a few microdeletion syndromes are also being screened but with less accuracy. Like every technology, cffDNA analysis is not entirely free of criticism. Its high testing cost, potential to accurately prognosticate the gender of the developing fetus and absence of standard testing practices will become an issue as the test becomes routine worldwide.

VANISHING TWIN SYNDROME RESULTS IN HIGHER RISK OF MISCARRIAGE EVEN FOLLOWING EUPLOID EMBRYO TRANSFER

Vanishing twin syndrome describes the loss of one twin during pregnancy that typically occurs during the first trimester. Risk factors for vanishing twin syndrome include fetal chromosome abnormalities and the transfer of multiple embryos during an IVF cycle. Outcomes of vanishing twin syndrome IVF pregnancies have been shown to result in more frequent premature delivery and babies with low birth weight. The aim of this study was to investigate the incidence of vanishing twin syndrome following euploid embryo transfers and the probability of pregnancy loss.

Does isolated nuchal translucency from 2.5 to 2.9mm increase the risk of fetal chromosome disease?

Increased fetal nuchal translucency (NT) is a common ultrasonic manifestation during pregnancy. Many studies have confirmed that NT ≥ 3mm is a high risk factor for adverse pregnancy outcome. However, when NT is between 2.5 and 2.9mm, will it increase the risk of fetal chromosome abnormalities and other diseases? What is the most appropriate method for prenatal chromosome evaluation? At present, it has not been widely reported in the literature, and the conclusion is also controversial. This prospective cohort study included fetal samples from women who underwent amniocentesis from 2017 to 2020. The samples of the experimental group were fetuses with NT ≥ 2.5mm at 11 to 13 + 6weeks of gestation, with or without ultrasonographic anomaly. The control group contained fetal NT < 2.5mm without ultrasonographic anomalies. All amniotic fluid samples were tested by copy number variants sequencing. In 262 fetal samples with isolated NT from 2.5 to 2.9mm, the detection rate of aneuploidy was 3.4% (9/262), and the risk of aneuploidy was significantly higher than that of the control group (1.4%, 32/2331) (relative risk 2.5, 95% CI 1.2-5.2). The detection rates of other pathogenic/likely pathogenic copy number variants in the two groups were 0.8% (2/262) and 1.3% (31/2331), respectively, which was not statistically significant (relative risk 0.6, 95% CI 0.1-2.4). Our results showed that isolated NT from 2.5 to 2.9mm increased the risk of fetal chromosome aneuploidy. Therefore, noninvasive prenatal screening is recommended as the first choice for prenatal chromosome evaluation in this population.

Prenatal diagnosis of trisomy 8 mosaicism, initially identified by cffDNA screening

BackgroundSo called cell-free fetal DNA (cffDNA) in the maternal plasma, which is derived from placenta, is widely used to screen fetal aneuploidies, including trisomy 21, 18, 13 and sex chromosomes. Here we reported a case of trisomy 8 mosaicism (T8M), which was initially identified via cffDNA screening in noninvasive prenatal testing (NIPT).MethodsA 35-year-old woman received cffDNA screening at 17th week of gestation. Amniocentesis was performed subsequently, and karyotyping, single-nucleotide polymorphism array (SNP-array) and BACs-on-Beads™ (BoBs™) were used to determine fetal chromosome content. Interphase fluorescence in situ hybridization (FISH) was applied to determine the copy number of chromosome 8.ResultsAn enhanced risk for fetal trisomy 8 was identified by cffDNA screening in the studied pregnant woman. After amniocentesis trisomy 8 was found in 1 of 73 metaphases. SNP-array on DNA derived from cultured amniocytes and neonatal cord blood cells suggested the presence of T8M. Interphase FISH on native neonatal cord blood cells confirmed T8M with a percentage of 10%. The Bobs™ fluorescence data also suggested that 8q23-8q24 was amplified.ConclusionsThe current study shows that NIPT is suited to provide hints on rare autosomal trisomies, which have to be further validated and confirmed by other approaches.

Digital PCR and its applications in noninvasive prenatal testing.

In the past decade, digital PCR (dPCR), as a new nucleic acid absolute quantification technology, has been widely used in clinical research. dPCR does not rely on the standard curve and has a higher tolerance to inhibitors. Therefore, it is more accurate than quantitative real-time PCR (qPCR) for the absolute quantification of target sequences. In this article, we aim to review the application of dPCR in noninvasive prenatal testing (NIPT). We focused on the progress of dPCR in screening and identifying fetal chromosome aneuploidies and monogenic mutations. We introduced some common strategies for dPCR in NIPT and analyzed the advantages and disadvantages of different methods. In addition, we compared dPCR with qPCR and next-generation sequencing, respectively, and described their superiority and shortcomings in clinical applications. Finally, we envisaged what the future of dPCR might be in NIPT. Although dPCR can provide reproducible results with improved accuracy due to the digital detection system, it is essential to combine the merits of dPCR and other molecular techniques to achieve more effective and accurate prenatal diagnostic strategies.

A fetal fraction enrichment method reduces false negatives and increases test success rate of fetal chromosome aneuploidy detection in early pregnancy loss

ObjectiveWe and others have previously demonstrated that the size-selection enrichment method could remarkably improve fetal fraction (FF) in the early gestational age (GA, 12–13 weeks), suggesting that 9 or 10 weeks should not be used as a threshold for GA in size-selection noninvasive prenatal screening (NIPS). Here, we assessed whether this method was reliable for detecting fetal chromosomal aneuploidy at the earliest GA (6–8 weeks).MethodsSize-selection NIPS for fetal chromosomal aneuploidy was applied to 208 pregnancy plasma samples (102 male and 106 female fetuses), while the 169 pregnancy samples with male fetuses also underwent standard NIPS. Multivariable linear regression models were used to evaluate the association between fold-change of FF and experimental factors.ResultsThe sensitivity of the cell-free DNA (cfDNA) test in detecting aneuploidy was 100% when screened with FF enrichment, whereas the sensitivity of the same patients was only 62.5% (5/8) without FF enrichment. In the 102 pregnancy samples with male fetuses, FF increased from 6.1% to 15.7%, and the median increase in FF was 2.8-fold with enrichment. Moreover, there was a trend toward an increasing success rate of the cfDNA test from 6 to 13 weeks of gestation, especially when the test success rate reached 100% after 7 weeks with FF enrichment. Multivariate linear regression analysis demonstrated that a lower initial FF, shorter cfDNA size, increased body mass index (BMI), and later GA were all independent predictors of a higher fold-change of FF. Compared with ≤ 120 bp cfDNA fragments, the mean fold-change of FF differences was 0.820 for 121–125 bp, 0.229 for 126–130 bp, − 0.154 for 131–135 bp, − 0.525 for 136–140 bp and − 0.934 for > 140 bp (Ptrend < 0.0001), suggesting that fold-change of FF significantly decreased with cfDNA fragments > 125 bp. These results were statistically significant after adjusting for confounding factors in the models for fold-change of FF.ConclusionsThe FF enrichment method is a reasonable strategy to detect fetal chromosomal aneuploidy in early pregnancy loss with reduced false negatives and increased test success rate after 7 weeks of GA and should be recommended for patients with early pregnancy loss.

Cell-free DNA screening positive for monosomy X: clinical evaluation and management of suspected maternal or fetal Turner syndrome

Initially provided as an alternative to evaluation of serum analytes and nuchal translucency for the assessment of pregnancies at high risk of trisomy 21, cell-free DNA screening for fetal aneuploidy, also referred to as noninvasive prenatal screening, can now also screen for fetal sex chromosome anomalies such as monosomy X as early as 9 to 10 weeks of gestation. Early identification of Turner syndrome, a sex chromosome anomaly resulting from the complete or partial absence of the second X chromosome, allows medical interventions such as optimizing obstetrical outcomes, hormone replacement therapy, fertility preservation and support, and improved neurocognitive outcomes. However, cell-free DNA screening for sex chromosome anomalies and monosomy X in particular is associated with high false-positive rates and low positive predictive value. A cell-free DNA result positive for monosomy X may represent fetal Turner syndrome, maternal Turner syndrome, or confined placental mosaicism. A positive screen for monosomy X with discordant results of diagnostic fetal karyotype presents unique interpretation and management challenges because of potential implications for previously unrecognized maternal Turner syndrome. The current international consensus clinical practice guidelines for the care of individuals with Turner syndrome throughout the lifespan do not specifically address management of individuals with a cell-free DNA screen positive for monosomy X. This study aimed to provide context and expert-driven recommendations for maternal and/or fetal evaluation and management when cell-free DNA screening is positive for monosomy X. We highlight unique challenges of cell-free DNA screening that is incidentally positive for monosomy X, present recommendations for determining if the result is a true-positive, and discuss when diagnosis of Turner syndrome is applicable to the fetus vs the mother. Whereas we defer the subsequent management of confirmed Turner syndrome to the clinical practice guidelines, we highlight unique considerations for individuals initially identified through cell-free DNA screening.

Prenatal screening and diagnosis for a fetus with mosaic sex chromosome abnormality

To carry out prenatal screening and diagnosis for a woman with advanced maternal age. Non-invasive prenatal testing (NIPT) was carried out to determine the risk of fetal chromosome aneuploidy. Aminiocentesis was proceeded for fetal chromosomal karyotyping and copy number variation sequencing (CNV-seq). The fetus was subjected to systematic ultrasound screening in the second trimester. NIPT has indicated there was a loss of fetal sex chromosome. Karotyping of the amniocyte showed a mosaic sex chromosome abnormality 45,X[53]/46,X,+mar[7]. The result of fetal DNA CNV-seq was seq[GRCh37]del(Yq11.1q12) chrY: g.13 104 553-28 819 361del, seq[GRCh37]del(Yp11.32p11.2) chrY: g.10 001-9 873 915del (mosaic ratio: 30%). Ultrasonography discovered that the fetus had renal dysplasia and male external genitalia. The karyotypes of the couple were both normal. Multiple genetic tests should be carried out for fetus with a high risk for chromosome aneuploidies signaled by NIPT. It is difficult to predict the post-natal phenotype for fetuses with mosaic sex chromosomal aneuploidies. The couple should be carefully counseled upon genetic counseling.

Hysteroembryoscopy and hysteroscopic uterine evacuation of early pregnancy loss: A feasible procedure in selected cases.

Hysteroscopic uterine evacuation of early pregnancy loss using tissue removal devices seems to be a safe and feasible procedure in selected cases. The hysteroscopic approach allows the precise localisation of the gestational sac inside the uterine cavity. The endoscopic approach allows one to perform hysteroembryoscopy before uterine evacuation and this technique appears to be more accurate than dilatation & curettage for fetal chromosome karyotyping, with lower maternal cell contamination. This "under vision" procedure may reduce retained products of conception rates and risk of intrauterine adhesions formation.