Disruption of maternal vascular remodeling by a fetal endoretrovirus-derived gene in preeclampsia.

BACKGROUND: Preeclampsia, one of the most lethal pregnancy-related diseases, is associated with the disruption of uterine spiral artery remodeling during placentation. However, the early molecular events leading to preeclampsia remain unknown. RESULTS: By analyzing placentas from preeclampsia, non-preeclampsia, and twin pregnancies with selective intrauterine growth restriction, we show that the pathogenesis of preeclampsia is attributed to immature trophoblast and maldeveloped endothelial cells. Delayed epigenetic reprogramming during early extraembryonic tissue development leads to generation of excessive immature trophoblast cells. We find reduction of de novo DNA methylation in these trophoblast cells results in selective overexpression of maternally imprinted genes, including the endoretrovirus-derived gene PEG10 (paternally expressed gene 10). PEG10 forms virus-like particles, which are transferred from the trophoblast to the closely proximate endothelial cells. In normal pregnancy, only a low amount of PEG10 is transferred to maternal cells; however, in preeclampsia, excessive PEG10 disrupts maternal vascular development by inhibiting TGF-beta signaling. CONCLUSIONS: Our study reveals the intricate epigenetic mechanisms that regulate trans-generational genetic conflict and ultimately ensure proper maternal-fetal interface formation.

Epigenetic phenotype of plasma cell-free DNA in the prediction of early-onset preeclampsia.

BACKGROUND: In the current study, we sought to characterise the methylation haplotypes and nucleosome positioning patterns of placental DNA and plasma cell-free DNA of pregnant women with early-onset preeclampsia using whole genome bisulphite sequencing (WGBS) and methylation capture bisulphite sequencing (MCBS) and further develop and examine the diagnostic performance of a generalised linear model (GLM) by incorporating the epigenetic features for early-onset preeclampsia. METHODS: This case-control study recruited pregnant women aged at least 18 years who delivered their babies at our Hospital. In addition, non-pregnant women with no previous history of diseases were included. Placental samples of the villous parenchyma were taken at the time of delivery and venous blood was drawn from pregnant women during non-invasive prenatal testing at 12-15 weeks of pregnancy and nonpregnant women during the physical check-up. WGBS and MCBS were carried out of extracted genomic DNA. Then, we established the GLM by incorporating preeclampsia-specific methylation haplotypes and nucleosome positioning patterns and examined the diagnostic performance of the model by receiver operating characteristic (ROC) curve analysis. RESULTS: The study included 135 pregnant women and 50 non-pregnant women. Our high-depth MCBS revealed notably different DNA methylation and nucleosome positioning patterns between women with and without preeclampsia. Preeclampsia-specific hypermethylated sites were found predominantly in the promoter regions and particularly enriched in CTCF on the X chromosome. Totally, 2379 preeclampsia-specific methylation haplotypes were found across the entire genome. ROC analysis showed that the area under the ROC curve (AUC) was 0.938 (95%CI 0.877, 1.000). At a GLM cut-off of 0.341, the AUC was the maximum, with a sensitivity of 95.6% and a specificity of 89.7%. CONCLUSION: Pregnant women with early-onset preeclampsia exhibit DNA methylation and nucleosome positioning patterns in placental and plasma DNA.

Early-onset preeclampsia is a potentially dangerous condition that can have a profound impact on the health of both the expectant mother and her unborn child. This condition is particularly concerning because it's challenging to predict who may be affected using conventional methods such as monitoring blood pressure. In our research, we've developed an innovative, non-invasive approach to predict the onset of early preeclampsia. We do this by analysing the genetic material of the developing baby, which can be found in the mother's blood. Our method has shown remarkable accuracy in our testing populations, and its implications are substantial. By providing an early warning system, this breakthrough can benefit pregnant women immensely. It means that early-onset preeclampsia can be identified and addressed well before it becomes a serious health threat. This allows for timely medical interventions and treatments, significantly improving the well-being of both mothers and their precious little ones.

Prenatal diagnosis of Down syndrome combined with transient abnormal myelopoiesis in foetuses with a GATA1 gene variant: two case reports.

BACKGROUND: Down syndrome myeloid hyperplasia includes transient abnormal myelopoiesis (TAM) and the myeloid leukemia associated with Down syndrome (ML-DS). The mutation of GATA1 gene is essential in the development of Down syndrome combined with TAM or ML-DS. Some patients with TAM are asymptomatic and may also present with severe manifestations such as hepatosplenomegaly and hydrops. CASE PRESENTATION: We report two cases of prenatally diagnosed TAM. One case was a rare placental low percentage 21 trisomy mosiacism, resulting in the occurrence of a false negative NIPT. The final diagnosis was made at 36 weeks of gestation when ultrasound revealed significant enlargement of the foetal liver and spleen and an enlarged heart; the foetus eventually died in utero. We detected a placenta with a low percentage (5-8%) of trisomy 21 mosiacism by Copy Number Variation Sequencing (CNV-seq) and Fluorescence in situ hybridization (FISH). In another case, foetal oedema was detected by ultrasound at 31 weeks of gestation. Two foetuses were diagnosed with Down syndrome by chromosomal microarray analysis via umbilical vein puncture and had significantly elevated cord blood leucocyte counts with large numbers of blasts. The GATA1 Sanger sequencing results suggested the presence of a [NM_002049.4(GATA1):c.220G > A (p. Val74Ile)] hemizygous variant and a [NM_002049.4(GATA1):c.49dupC(p. Gln17ProfsTer23)] hemizygous variant of the GATA1 gene in two cases. CONCLUSION: It seems highly likely that these two identified mutations are the genetic cause of prenatal TAM in foetuses with Down syndrome.

Performance of noninvasive prenatal testing for twin pregnancies in South China.

OBJECTIVE: The purpose of this study was to evaluate the performance of noninvasive prenatal testing (NIPT) for the detection of chromosomal aneuploidies and copy number variations (CNVs) in twin pregnancies. METHOD: A cohort of 2010 women with twin pregnancies was recruited. 1331 patients opted for NIPT, and 679 patients opted for expanded NIPT (NIPT-plus). All high-risk patients were advised to undergo invasive prenatal diagnosis. All participants were followed up until 6 months after birth. RESULTS: Twenty-two cases were predicted to have a high risk of chromosome abnormalities by NIPT, of which 14 pregnant women underwent invasive prenatal diagnosis. The 14 cases included 3 cases of trisomy 21, 1 case of trisomy 18, 1 case of trisomy 7, 2 cases of sex chromosome aneuploidies (SCAs), and 7 cases of CNVs, of which the confirmed cases numbered 2, 1, 0, 1, and 0, respectively. Twenty cases were predicted to have a high risk of chromosome abnormalities by NIPT-plus, of which 16 pregnant women underwent invasive prenatal diagnosis. The 16 cases included 1 case of trisomy 21, 1 case of trisomy 7, 7 cases of SCAs, and 7 cases of CNVs, of which were confirmed in 1, 0, 3, and 2, respectively. No false-negative result was reported during the follow-up period. CONCLUSION: The NIPT/NIPT-plus has excellent performance in the detection of chromosome aneuploidies in twin pregnancies. But for CNVs, the effectiveness of NIPT is poor, and the NIPT-plus have a certain detection efficiency. It is worth noting that pre- and post-genetic counseling is especially important, and the chorionicity, mode of conception, clinical indications, and fetal fraction should be considered as influencing factors.

Association between cell-free DNA fetal fraction and pregnant character: a retrospective cohort study of 27,793 maternal plasmas.

To determine the association between cell-free DNA fetal fraction (cffDNA) and various prenatal characters to better guide the clinical application of noninvasive prenatal screening (NIPS), a retrospective cohort study of 27,793 women with singleton pregnancies was conducted. Results indicated that no significant difference on cffDNA between trisomy/sex chromosome aneuploidy (SCA) and non-trisomy groups was found. However, the fetal fraction (FF) in the T18 and T13 subgroups were significantly lower than that in the non-trisomy group, while the FF in the T21 group was significantly higher than the non-trisomy group. Pearson's correlation analysis revealed a positive correlation between √FF and gestational week in the T21, SCA, and non-trisomy groups. A negative correlation between maternal age and √FF in T21 and non-trisomy cases was found, but a positive correlation in SCA group. Compared to the decreasing trend in FF in the T21 group, no significant difference was observed in the SCA group. The √FF level was negatively correlated to maternal BMI in T21 and non-trisomy group, while a positive correlation in SCA group. FF was close related to the result of NIPS and related maternal factors. Though NIPS has increased accuracy, the complexity still should be recognized especially in clinical practice.

Combined fetal fraction to analyze the Z-score accuracy of noninvasive prenatal testing for fetal trisomies 13, 18, and 21.

OBJECTIVE: This study aims to evaluate the correlation combined fetal fraction and Z-score for fetal trisomies 13, 18, and 21 of NIPT by the semiconductor sequencing platform and further analyze the differences of different sequencing depths. METHODS: A cohort of 61,581 pregnancies were recruited for NIPT. Invasive prenatal diagnostic confirmation is recommended in all high-risk NIPT cases. Logistic regression and rank correlation analysis were applied to analyze the relationship between different parameters. ROC curve analysis was adopted to analyze the cutoff values of Z-score and fetal fraction. RESULTS: A total of 278 common trisomy pregnancies were verified in 377 NIPT-positive results. The fitted logistic regression models revealed that Z-scores of NIPT-positive results were significantly associated with PPVs (p < 0.05). The ROC curve analysis showed that the optimal cutoff value of Z-scores for T21, T18, and T13 was 7.597, 4.944, and 9.135 for NIPT and 9.489, 8.004, and 12.4 for NIPT-plus. If combing fetal fraction as another evaluation factor, the PPV of trisomy 21 gradually improved. We analyzed the correlation between the fetal fraction and the PPV, which revealed that the fetal fraction was significantly correlated with PPV. By analyzing the PPV of different groups divided by the associated criteria obtained from ROC curve, the PPV of high Z-score and high fetal fraction is higher in groups of Z-score > the optimal cutoff value. CONCLUSION: The results of this study show that the fetal fraction is significantly correlated with the PPV. Combining fetal fraction with Z-score is significantly better than in groups of Z-score-associated criteria; clinicians can give more accurate and efficient prenatal genetic counseling.

Non-Invasive Prenatal Diagnosis of Monogenic Disorders Through Bayesian- and Haplotype-Based Prediction of Fetal Genotype.

Background: Non-invasive prenatal diagnosis (NIPD) can identify monogenic diseases early during pregnancy with negligible risk to fetus or mother, but the haplotyping methods involved sometimes cannot infer parental inheritance at heterozygous maternal or paternal loci or at loci for which haplotype or genome phasing data are missing. This study was performed to establish a method that can effectively recover the whole fetal genome using maternal plasma cell-free DNA (cfDNA) and parental genomic DNA sequencing data, and validate the method's effectiveness in noninvasively detecting single nucleotide variations (SNVs), insertions and deletions (indels). Methods: A Bayesian model was developed to determine fetal genotypes using the plasma cfDNA and parental genomic DNA from five couples of healthy pregnancy. The Bayesian model was further integrated with a haplotype-based method to improve the inference accuracy of fetal genome and prediction outcomes of fetal genotypes. Five pregnancies with high risks of monogenic diseases were used to validate the effectiveness of this haplotype-assisted Bayesian approach for noninvasively detecting indels and pathogenic SNVs in fetus. Results: Analysis of healthy fetuses led to the following accuracies of prediction: maternal homozygous and paternal heterozygous loci, 96.2 ± 5.8%; maternal heterozygous and paternal homozygous loci, 96.2 ± 1.4%; and maternal heterozygous and paternal heterozygous loci, 87.2 ± 4.7%. The respective accuracies of predicting insertions and deletions at these types of loci were 94.6 ± 1.9%, 80.2 ± 4.3%, and 79.3 ± 3.3%. This approach detected pathogenic single nucleotide variations and deletions with an accuracy of 87.5% in five fetuses with monogenic diseases. Conclusions: This approach was more accurate than methods based only on Bayesian inference. Our method may pave the way to accurate and reliable NIPD.

[Analysis of the results of chromosomal trisomies 21, 18 and 13 screening among 40 628 women by non-invasive prenatal testing].

OBJECTIVE: To assess the clinical value of non-invasive prenatal testing (NIPT) for the screening of trisomy and copy number variations (CNVs) of chromosomes 21, 18 and 13. METHODS: From January 2015 to December 2019, 40 628 pregnant women underwent NIPT testing using high-throughput sequencing and bioinformatics analysis to test the cell-free fetal DNA in maternal plasma. High-risk pregnant women underwent invasive prenatal diagnosis, while low-risk ones were followed up by telephone. RESULTS: The three most common indications included intermediate risk of serological screening, high risk of serological screening and advanced maternal age. Among all pregnant women, 257 cases were detected as trisomy 21, 18 and 13 (170, 49 and 38 cases, respectively). 227 cases chose invasive prenatal diagnosis, with respectively 122, 28 and 10 cases confirmed. The positive predictive value (PPV) was 81.33% (122/150), 65.12% (28/43), 29.41% (10/34), respectively. Two false negative cases of trisomy 18 were found during follow-up. Meanwhile, NIPT has detected 46 cases (15, 16 and 15 cases, respectively) CNVs on chromosomes 21, 18 and 13, among which 37 cases underwent invasive prenatal diagnosis. There were 5, 3 and 5 positive cases, which yielded a PPV of 41.67% (5/12), 25%(3/12) and 33.33%(5/15), respectively. Two other chromosome CNVs were accidentally discovered among the false positive samples. CONCLUSION: The incidence of chromosomal abnormalities in the serological screening high-risk group was 52.02%, which was significantly higher than other groups. NIPT has a high sensitivity and specificity for the screening of trisomies 21, 18 and 13, while its accuracy for detecting CNVs of chromosomes 21, 18 and 13 needs to be improved. As a screening method, NIPT has a great clinical value, though there are still limitations of false positive and false negative results.Comprehensive pre- and post-test genetic counseling should be provided to the patients.

Outcomes of pregnancies with trisomy 16 mosaicism detected by NIPT: a series of case reports.

BACKGROUND: Trisomy 16 (T16) is thought to be the most frequent chromosome abnormality at conception, which is often associated with a high risk of abnormal outcomes. METHODS: A retrospective analysis of 14 cases with high risk of T16 by noninvasive prenatal testing (NIPT) was conducted. All cases in the analysis involved prenatal diagnosis, karyotyping and chromosomal microarray analysis. CASE REPORTS: NIPT detected 12 cases of T16 and 2 cases of T16 mosaicism. Prenatal diagnosis confirmed 5 true positive cases and 9 false positive cases. Among the 5 true positive cases, 3 cases had ultrasound abnormalities. All of the 9 false positive cases continued their pregnancies. The newborns who were from these 9 false positive cases except 1 case (case 7) had low birth weights (< 2.5 kg) and there were also 2 premature deliveries. CONCLUSION: NIPT serves as a fast and early prenatal screening method, giving clues to chromosome abnormalities and providing guidance for managing pregnancy. Confined placental mosaicism in 16 pregnancies may be at higher risk for preterm delivery.

[Consensus on technological standards for non-invasive prenatal screening of pathogenic copy number variations by high-throughput sequencing of maternal plasma cell-free DNA].

Genomic disorders caused by pathogenic copy number variation (pCNV) have proven to underlie a significant proportion of birth defects. With technological advance, improvement of bioinformatics analysis procedure, and accumulation of clinical data, non-invasive prenatal screening of pCNV (NIPS-pCNV) by high-throughput sequencing of maternal plasma cell-free DNA has been put to use in clinical settings. Specialized standards for clinical application of NIPS-pCNV are required. Based on the discussion, 10 pCNV-associated diseases with well-defined conditions and 5 common chromosomal aneuploidy syndromes are recommended as the target of screening in this consensus. Meanwhile, a standardized procedure for NIPS-pCNV is also provided, which may facilitate propagation of this technique in clinical settings.

Performances of NIPT for copy number variations at different sequencing depths using the semiconductor sequencing platform.

OBJECTIVE: To evaluate the performance of noninvasive prenatal testing (NIPT) and NIPT-PLUS for the detection of genome-wide microdeletion and microduplication syndromes (MMSs) at different sequencing depths. The NIPT sequencing depth was 0.15X, and the data volume was 3 million reads; the NIPT-PLUS sequencing depth was 0.4X, and the data volume was 8 million reads. METHODS: A cohort of 50,679 pregnancies was recruited. A total of 42,969 patients opted for NIPT, and 7710 patients opted for NIPT-PLUS. All high-risk cases were advised to undergo invasive prenatal diagnosis and were followed up. RESULTS: A total of 373 cases had a high risk of a copy number variation (CNV) as predicted by NIPT and NIPT-PLUS: NIPT predicted 250 high-risk CNVs and NIPT-PLUS predicted 123. NIPT-PLUS increased the detection rate by 1.02% (0.58% vs 1.60%, p < 0.001). A total of 291 cases accepted noninvasive prenatal diagnosis, with 197 cases of NIPT and 94 cases of NIPT-PLUS. The PPV of CNV > 10 Mb for NIPT-PLUS was significantly higher than that for NIPT (p = 0.02). The total PPV of NIPT-PLUS was 12.56% higher than that of NIPT (43.61% vs 30.96%, p = 0.03). CONCLUSION: NIPT-PLUS had a better performance in detecting CNVs in terms of the total detection rate and total PPV. However, great care must be taken in presenting results and providing appropriate counseling to patients when deeper sequencing is performed in clinical practice.

Noninvasive prenatal detection of fetal sex chromosome abnormalities using the semiconductor sequencing platform (SSP) in Southern China.

BACKGROUND: Noninvasive prenatal testing (NIPT) has been widely used to screen for fetal aneuploidies, including fetal sex chromosome aneuploidies (SCAs). However, there is less information on the performance of NIPT in detecting SCAs. METHODS: A cohort of 47,800 pregnancies was recruited to review the high-risk NIPT results for SCAs. Cell-free fetal DNA (cffDNA) was extracted and sequenced. All NIPT high-risk cases were recommended to undergo invasive prenatal diagnosis for karyotyping analysis and chromosome microarray analysis (CMA). RESULTS: A total of 238 high-risk cases were detected by NIPT, including 137 cases of 45,X, 27 cases of 47,XXX, and 74 cases of 47,XYY/47,XXY. Prenatal diagnosis, including karyotyping analysis and CMA, was available in 170 cases. The positive predictive value (PPV) was 30.00% for 45,X, 70.58% for 47,XXX, and 81.13% for 47,XYY/47,XXY. In addition, 13 cases of sex chromosome mosaicism and 9 cases of sex chromosome CNVs were incidentally found in this study. CONCLUSION: Our study showed that NIPT was reliable for screening SCAs based on a large sample, and it performed better in predicting sex chromosome trisomies than monosomy X. Our study will provide an important reference for clinical genetic counseling and further processing of the results.

Potential influence of parental copy number variations on noninvasive prenatal testing (NIPT): two case reports.

BACKGROUND: Small subchromosomal deletions and duplications caused by copy number variants (CNVs) can now be detected with noninvasive prenatal testing (NIPT) technology. However, the clinical utility and validity of this screening for CNVs are still unknown. Here, we discuss some special conditions in which both cases simultaneously exhibited false positives caused by maternal CNVs and false negatives due to limitations of the technology. CASE PRESENTATION: In case 1, NIPT indicated a 1.1 Mb deletion at 21q21.1, but the umbilical cord for array CGH (aCGH) revealed a 422 kb deletion at 15q13.3. Peripheral blood of the parents for aCGH showed a 1.1 Mb deletion at 21q21.1 in the mother's sample, and the same deletion at 15q13.3 was detected in the father's blood. In case 2, NIPT showed a 1.5 Mb deletion at 22q11.21, but aCGH of amniocytes revealed a 1.377 Mb duplication rather than a 1.5 Mb deletion at 22q11.21. Furthermore, aCGH analysis of the parental blood revealed a 647 kb deletion at 22q11.21 in the mother and a 2.8 Mb duplication of 22q11.21 in the father. CONCLUSIONS: Our findings not only highlight the significance of diagnostic testing following a positive cfDNA sequencing result but also the necessity for additional analytical and clinical validation before routine use in practice.

[The value of noninvasive prenatal screening for the detection of fetal chromosome 16 aneuploidy].

OBJECTIVE: To assess the value of non-invasive prenatal screening (NIPS) for the detection of fetal chromosome 16 aneuploidy through multi-method verification and follow-up of pregnancy outcomes. METHODS: From January 2016 to December 2017, 7972 pregnant women with singleton pregnancies accepted the NIPS test after 10th gestational week with informed consent. Those with fetal chromosome 16 abnormality suggestive by the NIPS test were subjected to prenatal diagnosis including chromosomal karyotyping and chromosomal microarray analysis (CMA). RESULTS: Of the 7972 pregnant women tested by NIPS, 16 (0.2%) were predicted to have fetal chromosome 16 abnormality. The average age of the 16 pregnant women was 33.5 ± 5.24, and the average gestational week was 19.88±2.47. Chromosomal karyotyping verified that 3 fetuses had mosaicisms and 1 carried pericentric inversion of chromosome 9, which yielded a positive predictive value (PPV) of 18.8%. CMA has detected 7 fetuses with genomic abnormalities, which yielded a PPV of 43.8%. Eleven of the 16 women (68.8%) have given birth to healthy babies. CONCLUSION: For pregnant women with a high risk of chromosome 16 aneuploidy suggested by NIPS, the prognosis of fetus should be evaluated by multiple methods. Compared with conventional karyotyping analysis, molecular methods such as CMA are far superior.

Noninvasive prenatal detection of hemoglobin Bart hydrops fetalis via maternal plasma dispensed with parental haplotyping using the semiconductor sequencing platform.

BACKGROUND: Thalassemia is one of the most common monogenetic diseases in the south of China and Southeast Asia. Hemoglobin Bart's hydrops fetalis syndrome was caused by a homozygous Southeast Asian deletion (-/-) in the HBA gene. Few studies have proved the potential of screen for Bart's hydrops fetalis using fetal cell-free DNA. However, the number of cases is still relatively small. Clinical trials of large samples would be needed. OBJECTIVE: In this study, we aimed to develop a noninvasive method of target-captured sequencing and genotyping by the Bayesian method using cell-free fetal DNA to identify the fetal genotype in pregnant women who are at risk of having hemoglobin Bart hydrops fetalis in a large-scale study. STUDY DESIGN: In total, 192,173 couples from 30 hospitals were enrolled in our study and 878 couples were recruited, among whom both the pregnant women and their husbands were detected to be carriers of Southeast Asian type (-/αα) of α-thalassemia. Prenatal diagnosis was performed by chorionic villus sampling, amniocentesis, or cordocentesis using gap-polymerase chain reaction considered as the golden standard. RESULTS: As a result, we found that the sensitivity and specificity of our noninvasive method were 98.81% and 94.72%, respectively, in the training set as well as 100% and 99.31%, respectively, in the testing set. Moreover, our method could identify all of 885 maternal samples with the Southeast Asian carrier and 36 trisomy samples with 100% of sensitivity in T13, T18, and T21 and 99.89% (1 of 917) and 99.88% (1 of 888) of specificity in T18 and T21, respectively. CONCLUSION: Our method opens the possibility of early screening for maternal genotyping of α-thalassemia, fetal aneuploidies in chromosomes 13/18/21, and hemoglobin Bart hydrops fetalis detection in 1 tube of maternal plasma.

Factors affecting cell-free DNA fetal fraction: statistical analysis of 13,661 maternal plasmas for non-invasive prenatal screening.

BACKGROUND: The identification of cell-free fetal DNA (cffDNA) facilitated non-invasive prenatal screening (NIPS) through analysis of cffDNA in maternal plasma. However, challenges regarding its clinical implementation become apparent. Factors affecting fetal fraction should be clarified to guide its clinical application. RESULTS: A total of 13,661 pregnant subjects with singleton pregnancies who undertook NIPS were included in the study. Relationship of gestational age, maternal BMI, and maternal age with the cffDNA fetal fraction in maternal plasmas for NIPS was investigated. Compared with 13 weeks (12.74%) and 14-18 weeks group (12.73%), the fetal fraction in gestational ages of 19-23 weeks, 24-28 weeks, and more than 29 weeks groups significantly increased to 13.11%, 16.14%, and 21.17%, respectively (P < 0.01). Compared with fetal fraction of 14.54% in the maternal BMI group of < 18.5 kg/m2, the percentage of fetal fraction in the group of 18.5-24.9 kg/m2 (13.37%), 25-29.9 kg/m2 (12.20%), 30-34.9 kg/m2 (11.32%), and 35-39.9 kg/m2 (11.57%) decreased significantly (P < 0.01). Compared with the fetal fraction of 14.38% in the group of 18-24 years old, the fetal fraction in the maternal age group of 25-29 years old group (13.98%) (P < 0.05), 30-34 years old group (13.18%) (P < 0.01), 35-39 years old group (12.34%) (P < 0.01), and ≥ 40 years old (11.90%) group (P < 0.01) decreased significantly. CONCLUSIONS: The percentage of fetal fraction significantly increased with increase of gestational age. Decreased fetal fraction with increasing maternal BMI was found. Maternal age was also negatively related to the fetal fraction.

Association between fetal fraction at the second trimester and subsequent spontaneous preterm birth.

OBJECTIVE: To evaluate the association between the fetal fraction of cell-free DNA at the second trimester and subsequent spontaneous preterm birth. METHODS: In this retrospective cohort study, data were collected from women with singleton pregnancies who underwent noninvasive prenatal testing at 14 to 25 weeks of gestation. The eligible patients were classified into three groups according to pregnancy outcome: birth at ≥37 weeks of gestation (term group), delivery at <34 weeks of gestation (early spontaneous preterm), and delivery at 34+0 to 36+6  weeks of gestation (late spontaneous preterm). Stepwise linear regression was performed to determine the maternal characteristics associated with the fetal fraction of cell-free DNA. Logistic regression was used to determine the relationship between the fetal fraction of cell-free DNA and pregnancy outcomes by adjusting for history of preterm birth. RESULTS: A total of 8129 singleton pregnancies met the recruitment criteria. Among them, 7790 (95.83%) were in the term group, 284 (3.49%) were in the late spontaneous preterm group, and 55 (0.68%) were in the early spontaneous preterm group. The fetal fraction of cell-free DNA was negatively correlated with body mass index, maternal age, nulliparity, and history of spontaneous preterm birth; positively correlated with gestational age; and not correlated with assisted reproduction or surface antigen of hepatitis B virus (HBsAg) positivity. After adjusting for history of preterm birth, a logistic regression analysis demonstrated no statistically significant associations between the fetal fraction of cell-free DNA and spontaneous preterm birth in any of the preterm groups (<34 weeks, 34+0 to 36+6  weeks, and <37 weeks). CONCLUSION: Our preliminary study found no relationship between the fetal fraction on NIPT at the second trimester and subsequent spontaneous preterm birth.

The significance of trisomy 7 mosaicism in noninvasive prenatal screening.

BACKGROUND: This study was an evaluation of the role of noninvasive prenatal testing (NIPT) in the detection of trisomy 7 in prenatal diagnosis. METHOD: A total of 35 consecutive cases underwent screening for trisomies by cell-free DNA testing between April 2015 and November 2017 due to suspicious NIPT results; these cases represented 0.11% of patients (35/31,250) with similar frequencies of abnormal results among the laboratories performing the tests. NIPT was offered to further screen for common fetal chromosomal abnormalities. Karyotype analysis, chromosomal microarray analysis (CMA), and next-generation sequencing (NGS) were used to detect 20, 14, and 25 patients, respectively, who accepted confirmatory diagnostic testing. RESULTS: High-risk results by NIPT were recorded for trisomy 7 alone in 29 women: dual aneuploidy in 4 patients and multiple aneuploidy in 2 patients. Karyotype analysis of amniotic fluid cells was normal in all 20 pregnancies, suggesting a probability of confined placental mosaicism. Further CMA data were obtained in 14 of the cases mentioned above, and 2 fetuses were detected with positive results with copy number variation. The NGS results suggested that all these samples were placental chimerisms of chromosome 7, except for one sample that was found to be an additional chimerism of chromosome 2, which was also consistent with the NIPT result. CONCLUSION: Our results may be useful for the counseling of pregnant women in the detection of trisomy 7 by NIPT.

Performance of non-invasive prenatal testing for trisomies 21 and 18 in twin pregnancies.

BACKGROUND: Cell-free fetal DNA in maternal plasma represents a source of fetal genetic material that can be sampled noninvasively. There are ample studies confirming the accuracy of NIPT in singleton pregnancies, but there is still relatively little studies demonstrate the feasibility and clinical application of a NIPT for fetal aneuploidy screening in twin pregnancies. RESULTS: In this study, we have finished 432 twin pregnancies screening by NIPT. There were 4 double chorionic dichorionic diamniotic (DCDA) cases of true positive NIPT results, including 1of T18 and 3 of T21, and 1 monochorionic diamniotic (MCDA) cases of true positive NIPT results, including 1of T21. The combined false-positive frequency for trisomies 21, 18 was 0%. Furthermore, there were 2 cases of false positive NIPT results, including 1 of T7 and 1 of sex chromosome aneuploidy. There was no false negative case, which gave a combined sensitivity and specificity of 100 and 99.53% respectively. CONCLUSION: Our study demonstrated NIPT performed well in the detection of trisomy 21 in twin pregnancy. It is feasible and clinical applicable of NIPT for fetal aneuploidy screening in twin pregnancies. But, it needs a large number of clinical samples to demonstrate the applicability of other chromosomal abnormalities besides trisomies 21 and 18 in both singleton pregnancies and twin pregnancies.

A case of placental trisomy 18 mosaicism causing a false negative NIPT result.

BACKGROUND: The non-invasive prenatal testing that evaluates circulating cell free DNA, and has been established as an additional pregnancy test for detecting the common fetal trisomies 21, 18 and 13 is rapidly revolutionizing prenatal screening as a result of its increased sensitivity and specificity. However, false positive and false negative results still exist. CASE PRESENTATION: We presented a case in which the non-invasive prenatal testing results were normal at 15 gestational age (GA), but an ultrasound examination at 30GA showed that the fetus had heart abnormalities, and the third trimester ultrasound at 33GA noted multiple anomalies including a 3.0 mm ventricular septal defect. Along with cordocentesis at 33GA, the cord blood sample cytogenetics analysis showed a mos 47,XN,+18[61]/46,XN[39] T18 karyotype. Six placental biopsies confirmed that the chromosome 18 placenta chimerism ratio had changed from 33% to 72%. Ultimately, the pregnancy was interrupted at 34GA. CONCLUSIONS: We presented this case to highlight the need to clearly explain false positive or false negative results to patients. We believe that this information will also influence the development of future diagnostic test methodologies.