scholarly journals Expanding the application of non-invasive prenatal testing in the detection of foetal chromosomal copy number variations

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Chaohong Wang ◽  
Junxiang Tang ◽  
Keting Tong ◽  
Daoqi Huang ◽  
Huayu Tu ◽  
...  
Keyword(s):  
Copy Number ◽  
Prenatal Testing ◽  
Trisomy 13 ◽  
Clinical Samples ◽  
Chromosomal Microarray Analysis ◽  
True Positive ◽  
Predictive Values ◽  
Non Invasive ◽  
Chromosome Aneuploidy

Abstract Purpose The aim of this study was to assess the detection efficiency and clinical application value of non-invasive prenatal testing (NIPT) for foetal copy number variants (CNVs) in clinical samples from 39,002 prospective cases. Methods A total of 39,002 pregnant women who received NIPT by next-generation sequencing (NGS) with a sequencing depth of 6 M reads in our centre from January 2018 to April 2020 were enrolled. Chromosomal microarray analysis (CMA) was further used to diagnose suspected chromosomal aneuploidies and chromosomal microdeletion/microduplication for consistency assessment. Results A total of 473 pregnancies (1.213%) were positive for clinically significant foetal chromosome abnormalities by NIPT. This group comprised 99 trisomy 21 (T21, 0.254%), 30 trisomy 18 (T18, 0.077%), 25 trisomy 13 (T13, 0.064%), 155 sex chromosome aneuploidy (SCA, 0.398%), 69 rare trisomy (0.177%), and 95 microdeletion/microduplication syndrome (MMS, 0.244%) cases. Based on follow-up tests, the positive predictive values (PPVs) for the T21, T18, T13, SCA, rare trisomy, and MMS cases were calculated to be 88.89%, 53.33%, 20.00%, 40.22%, 4.88%, and 49.02%, respectively. In addition, the PPVs of CNVs of < 5 Mb, 5–10 Mb, and > 10 Mb were 54.55%, 38.46%, and 40.00%, respectively. Among the 95 cases with suspected CNVs, 25 were diagnosed as true positive and 26 cases as false positive; follow-up prenatal diagnosis by CMA was not performed for 44 cases. Moreover, among the 25 true positive cases, 10 were pathogenic, 3 were likely pathogenic, and 12 were of uncertain significance. Conclusion NIPT is not only suitable for screening T21, T18, T13, and SCA but also has potential significance for CNV detection. As combined with ultrasound, extended NIPT is effective for screening MMS. However, NIPT should not be recommended for whole-chromosome aneuploidy screening.

scholarly journals A retrospective study of noninvasive prenatal testing for chromosome aneuploidies and subchromosomal copy number variations in 24359 single pregnancies

2020 ◽  
Author(s):  
yuefang Liu ◽  
Longfei Cheng ◽  
Yuan Peng ◽  
Zhe Liang ◽  
Xin Jin ◽  
...  
Keyword(s):  
Prenatal Diagnosis ◽  
Copy Number ◽  
False Negative ◽  
Prenatal Testing ◽  
Clinical Information ◽  
Copy Number Variations ◽  
Trisomy 13 ◽  
Chromosomal Microarray ◽  
Chromosomal Microarray Analysis

Abstract Background: With the development of whole-genome sequencing, small subchromosomal deletions and duplications could be found by non-invasive prenatal testing(NIPT). Our study is aimed to review the efficacy of NIPT as a screening test for aneuploidies and subchromosomal copy number variations (CNVs) in 24359 single pregnancies.Methods: A total of 24359 single pregnancies with different clinical features were retrospectively analyzed. Pathogenicity of abnormal NIPT results were assessed according to American College of Medical Genetics and Genomics(ACMG). Chromosome aneuploidies and subchromosomal CNVs were confirmed by karyotyping and chromosomal microarray analysis(CMA). Results: A total of 442 pregnancies (442/24359,1.9%) were with abnormal NIPT results. The positive predictive value (PPV) for trisomy 21(T21), trisomy 18 (T18), trisomy 13 (T13), and sex chromosome aneuploidies (SCAs) was 84.8%, 54.2%, 11.1% an 40.5% respectively. The PPV for subchromosomal CNVs was 59.0% (46/78). The clinical information, prenatal diagnosis results and follow-up results of 46 true positive cases, 6 cases with subchromosomal CNVs inconsistent with NIPT and 1 case of false negative were also demonstrated in detail.Conclusion: Our data have potential significance in demonstrating the significance of NIPT not only for common whole chromosome aneuploidies but also for subchromosomal CNV. Besides, the clinical information, prenatal diagnosis results and follow-up results of 52 cases with subchromosomal CNV and 1 case of false negative would provide important guidance for genetic counseling.

scholarly journals Expanded noninvasive prenatal testing for fetal aneuploidy and copy number variations and parental willingness for invasive diagnosis in a cohort of 18,516 cases

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yunsheng Ge ◽  
Jia Li ◽  
Jianlong Zhuang ◽  
Jian Zhang ◽  
Yanru Huang ◽  
...  
Keyword(s):  
Prenatal Diagnosis ◽  
High Risk ◽  
Pregnant Women ◽  
Copy Number ◽  
Prenatal Testing ◽  
Copy Number Variations ◽  
Trisomy 13 ◽  
Noninvasive Prenatal Testing ◽  
Predictive Values ◽  
Parental Willingness

Abstract Background Noninvasive prenatal testing (NIPT) has been wildly used to screen for common aneuplodies. In recent years, the test has been expanded to detect rare autosomal aneuploidies (RATs) and copy number variations (CNVs). This study was performed to investigate the performance of expanded noninvasive prenatal testing (expanded NIPT) in screening for common trisomies, sex chromosomal aneuploidies (SCAs), rare autosomal aneuploidies (RATs), and copy number variations (CNVs) and parental willingness for invasive prenatal diagnosis in a Chinese prenatal diagnosis center. Methods A total of 24,702 pregnant women were retrospectively analyzed at the Women and Children’s Hospital from January 2013 to April 2019, among which expanded NIPT had been successfully conducted in 24,702 pregnant women. The high-risk expanded NIPT results were validated by karyotype analysis and chromosomal microarray analysis. All the tested pregnant women were followed up for pregnancy outcomes. Results Of the 24,702 cases, successful follow-up was conducted in 98.77% (401/446) of cases with common trisomies and SCAs, 91.95% (80/87) of RAT and CNV cases, and 76.25% (18,429/24,169) of cases with low-risk screening results. The sensitivity of expanded NIPT was 100% (95% confidence interval[CI], 97.38–100%), 96.67%(95%CI, 82.78–99.92%), and 100%(95%CI, 66.37–100.00%), and the specificity was 99.92%(95%CI, 99.87–99.96%), 99.96%(95%CI, 99.91–99.98%), and 99.88% (95%CI, 99.82–99.93%) for the detection of trisomies 21, 18, and 13, respectively. Expanded NIPT detected 45,X, 47,XXX, 47,XXY, XYY syndrome, RATs, and CNVs with positive predictive values of 25.49%, 75%, 94.12%, 76.19%, 6.45%, and 50%, respectively. The women carrying fetuses with Trisomy 21/Trisomy 18/Trisomy 13 underwent invasive prenatal diagnosis and terminated their pregnancies at higher rates than those at high risk for SCAs, RATs, and CNVs. Conclusions Our study demonstrates that the expanded NIPT detects fetal trisomies 21, 18, and 13 with high sensitivity and specificity. The accuracy of detecting SCAs, RATs, and CNVs is still relatively poor and needs to be improved. With a high-risk expanded NIPT result, the women at high risk for common trisomies are more likely to undergo invasive prenatal diagnosis procedures and terminate their pregnancies than those with unusual chromosome abnormalities.

scholarly journals The Clinical Application of Non-invasive Prenatal Genetic Testing in the Screening of Fetal Chromosomal Diseases

2021 ◽  
Author(s):  
Yu Pang ◽  
chaohong wang ◽  
Junxiang Tang ◽  
Jiansheng Zhu
Keyword(s):  
High Risk ◽  
Clinical Application ◽  
Trisomy 21 ◽  
Sex Chromosome ◽  
Chromosomal Abnormalities ◽  
Reference Value ◽  
Prenatal Testing ◽  
Trisomy 13 ◽  
Non Invasive ◽  
Chromosome Aneuploidy

Abstract Objective：To explore the efficacy and clinical application value of non-invasive prenatal testing (non-invasive prenatal testing, NIPT) for screening fetal chromosomal abnormalities. Methods: NIPT was performed on 25,517 pregnant women. The high-risk samples were compared with amniotic fluid and cord blood chromosome karyotype analysis. Some samples were further verified by microarray (CMA), and pregnancy outcomes were followed up. Results: Of all the cases examined, 25502 cases were detected successfully, and a total of 294 high-risk samples (1.15%) were detected, of which further diagnosis was made in 208 cases, true positive samples were detected in 96 cases, and further tests were refused in 86 cases.71 cases (0.28%) of autosomal aneuploid high-risk samples were detected and 51 cases were diagnosed, including 44 cases of trisomy 21 (T21), 5 cases of trisomy 18 (T18), and 2 cases of trisomy 13 (T13). The PPV was 90.90%, 45.45% and 33.33%, respectively. Thirteen high-risk samples of trisomy 21, 18, and 13 were detected, and 1 case was confirmed as T21 mosaic PPV was 8.33% NPV was 100%. High-risk samples of sex chromosome aneuploidy (SCA) were detected in 72 cases (0.28%), 23 cases were diagnosed, and the PPV was 40.07%. The PPV was 12.00%, 50.00%, 72.73% and 75.00%, respectively, and the PPV was 12.00%, 50.00%, 72.73% and 75.00%, respectively. High-risk samples of copy number variation (CNV) were detected in 104 cases (0.41%), and 18 cases were diagnosed, with a PPV of 32.14%. Other high-risk samples of chromosome aneuploidy were detected in 34 cases (0.13%), and 3 cases were diagnosed as T2, T9, and T16, respectively. PPV is 8.70%.Conclusion: NIPT is suitable for trisomy 21, 18, and 13 screening, especially for T21. It also has a certain reference value for SCA and microdeletion and microduplication syndromes（MMS）, and it is not recommended for screening for other chromosomal aneuploidies.

scholarly journals Analysis of Prenatal Diagnosis Results and Pregnancy Outcome of Non-invasive Prenatal Screening High-risk Fetuses

2020 ◽  
Author(s):  
Yan Luo ◽  
Yanmei Sun ◽  
Haishen Tian ◽  
Hezhen Lu ◽  
Lishuang Ma ◽  
...  
Keyword(s):  
Prenatal Diagnosis ◽  
High Risk ◽  
Pregnant Women ◽  
Clinical Significance ◽  
Prenatal Screening ◽  
Trisomy 13 ◽  
Chromosomal Microarray Analysis ◽  
Non Invasive ◽  
Chromosomal Karyotype

Abstract BackgroundWith the development of whole-genome sequencing, small chromosomal deletions and duplications could be found by NIPT. This study is to evaluate the clinical significance of fetal chromosomal karyotype analysis and chromosomal microarray analysis (CMA) to clarify the clinical significance of 528 cases of high-throughput sequencing noninvasive prenatal screening suggesting high-risk cases. MethodsNon-invasive prenatal screening showed that the fetus 21, 18, 13, sex chromosomes, and other chromosomes are at high risk of aneuploidy and fetal chromosome copy number variations (CNVs) are at high risk, requiring prenatal diagnosis Pregnant women are the research objects. After obtaining informed consent, fetal cells were obtained by amniocentesis or umbilical vein puncture for chromosomal karyotype and CMA analysis. All cases of childbirth were followed up by telephone over a period of 1 year.Results Among 528 fetuses, 447 were at high risk of aneuploidy. The positive predictive value (PPV) for trisomy 21(T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosome aneuploidies (SCAs), and other chromosome aneuploidy was 85.24%, 51.52%, 12.5%, 50.82%, and 5.88% respectively. Another 81 cases of non-invasive prenatal screening suggest CNVs High risk. The PPV for CNVs was 34.57% .Among them, CNVs has a clear pathogenic significance can reach 24.69% . Follow-up of childbirth cases: Of the 62 pregnant women diagnosed with fetal SCA, 13 chose to continue their pregnancy, and the overall continued pregnancy rate was 20.97% (13/62); CNVs has no clear significance/no disease reported in 8 cases, 1 case After being lost to follow-up, all 7 cases chose to continue their pregnancy. One of the children was not informed about the specific situation; one girl had six fingers on both hands, and the rest had no abnormal growth; the remaining five children developed normally. ConclusionThis study has obtained relatively reliable PPV data for NIPT screening for chromosomal aneuploidy, which provides a reliable basis for clinical genetic counseling and treatment; it is recommended to perform prenatal diagnosis and perform chromosomal nucleus when non-invasive and high-risk prompts suspicious chromosomal abnormalities (over/under/microdeletion/microduplication). Type and CMA inspection, so that the inspection is more comprehensive and not easy to miss the diagnosis.

scholarly journals Expanding the Scope of Non-invasive Prenatal Testing to Detect Fetal Chromosomal Copy Number Variations

2021 ◽  
Vol 8 ◽  
Author(s):  
Songchang Chen ◽  
Lanlan Zhang ◽  
Jiong Gao ◽  
Shuyuan Li ◽  
Chunxin Chang ◽  
...  
Keyword(s):  
Copy Number ◽  
Detection Rate ◽  
Prenatal Testing ◽  
Read Depth ◽  
Copy Number Variations ◽  
Chromosomal Microarray ◽  
Chromosomal Microarray Analysis ◽  
Non Invasive ◽  
Positive Detection Rate ◽  
Cnv Detection

Non-invasive prenatal testing (NIPT) for common fetal trisomies is effective. However, the usefulness of cell-free DNA testing to detect other chromosomal abnormalities is poorly understood. We analyzed the positive rate at different read depths in next-generation sequencing (NGS) and identified a strategy for fetal copy number variant (CNV) detection in NIPT. Pregnant women who underwent NIPT by NGS at read depths of 4–6 M and fetuses with suspected CNVs were analyzed by amniocentesis and chromosomal microarray analysis (CMA). These fetus samples were re-sequenced at a read depth of 25 M and the positive detection rate was determined. With the increase in read depth, the positive CNV detection rate increased. The positive CNV detection rates at 25 M with small fragments were higher by NGS than by karyotype analysis. Increasing read depth in NGS improves the positive CNV detection rate while lowering the false positive detection rate. NIPT by NGS may be an accurate method of fetal chromosome analysis and reduce the rate of birth defects.

scholarly journals Performance of Cell-Free DNA Screening for Fetal Common Aneuploidies and Sex Chromosomal Abnormalities: A Prospective Study from a Less Developed Autonomous Region in Mainland China

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 478
Author(s):  
Yunli Lai ◽  
Xiaofan Zhu ◽  
Sheng He ◽  
Zirui Dong ◽  
Yanqing Tang ◽  
...  
Keyword(s):  
Sex Chromosome ◽  
Chromosomal Abnormalities ◽  
False Negative ◽  
Prenatal Testing ◽  
Read Depth ◽  
Trisomy 13 ◽  
Prognostic Information ◽  
Aneuploidy Screening ◽  
Predictive Values ◽  
Risk Result

To evaluate the performance of noninvasive prenatal screening (NIPS) in the detection of common aneuploidies in a population-based study, a total of 86,262 single pregnancies referred for NIPS were prospectively recruited. Among 86,193 pregnancies with reportable results, follow-up was successfully conducted in 1160 fetuses reported with a high-risk result by NIPS and 82,511 cases (95.7%) with a low-risk result. The screen-positive rate (SPR) of common aneuploidies and sex chromosome abnormalities (SCAs) provided by NIPS were 0.7% (586/83,671) and 0.6% (505/83,671), respectively. The positive predictive values (PPVs) for Trisomy 21, Trisomy 18, Trisomy 13 and SCAs were calculated as 89.7%, 84.0%, 52.6% and 38.0%, respectively. In addition, less rare chromosomal abnormalities, including copy number variants (CNVs), were detected, compared with those reported by NIPS with higher read-depth. Among these rare abnormalities, only 23.2% (13/56) were confirmed by prenatal diagnosis. In total, four common trisomy cases were found to be false negative, resulting in a rate of 0.48/10,000 (4/83,671). In summary, this study conducted in an underdeveloped region with limited support for the new technology development and lack of cost-effective prenatal testing demonstrates the importance of implementing routine aneuploidy screening in the public sector for providing early detection and precise prognostic information.

scholarly journals Clinical characterization of chromosome 5q21.1–21.3 microduplication: A case report

Open Medicine ◽  
2020 ◽  
Vol 15 (1) ◽  
pp. 1123-1127
Author(s):  
Shuang Chen ◽  
Yang Yu ◽  
Han Zhang ◽  
Leilei Li ◽  
Yuting Jiang ◽  
...  
Keyword(s):  
Case Report ◽  
Microarray Analysis ◽  
Prenatal Testing ◽  
Chromosomal Microarray ◽  
Chromosomal Microarray Analysis ◽  
Chromosome 5 ◽  
Left Lateral Ventricle ◽  
Pulsed Doppler Ultrasound

AbstractChromosomal microdeletions and microduplications likely represent the main genetic etiologies for children with developmental delay or intellectual disability. Through prenatal chromosomal microarray analysis, some microdeletions or microduplications can be detected before birth to avoid unnecessary abortions or birth defects. Although some microdeletions or microduplications of chromosome 5 have been reported, numerous microduplications remain undescribed. We describe herein a case of a 30-year-old woman carrying a fetus with a chromosome 5q21.1–q21.3 microduplication. Because noninvasive prenatal testing indicated a fetal chromosome 5 abnormality, the patient underwent amniocentesis at 22 weeks 4 days of gestation. Karyotyping and chromosomal microarray analysis were performed on amniotic fluid cells. Fetal behavioral and structural abnormalities were assessed by color and pulsed Doppler ultrasound. Clinical characteristics of the newborn were assessed during the follow-up. The left lateral ventricle appeared widened on ultrasound, but the infant appeared normal at birth. The 5q21.1–q21.3 microduplication in the fetus was inherited from his mother. There are seven genes in this duplication region, but their main functions are unclear. According to this case report, microduplication in this region could represent a benign mutation. Clinicians should pay attention to the breakpoints and the genes involved when counseling patients with microdeletions and microduplications.

scholarly journals Follow-up in Patients With Non-invasive Prenatal Screening Failures: A Reflection on the Choice of Further Prenatal Diagnosis

2021 ◽  
Vol 12 ◽  
Author(s):  
Sha Liu ◽  
Hongqian Liu ◽  
Jianlong Liu ◽  
Ting Bai ◽  
Xiaosha Jing ◽  
...  
Keyword(s):  
Genetic Counseling ◽  
Prenatal Diagnosis ◽  
Pregnant Women ◽  
Prenatal Screening ◽  
Chromosomal Abnormalities ◽  
Detection Methods ◽  
Chromosomal Microarray ◽  
Chromosomal Microarray Analysis ◽  
Non Invasive

BackgroundOur aim was to provide a theoretical basis for clinicians to conduct genetic counseling and choose further prenatal diagnosis methods for pregnant women who failed non-invasive prenatal screening (NIPS).MethodsA retrospective analysis was performed on pregnant women who had failed NIPS tests.ResultsAmong the 123,291 samples, 394 pregnant women did not obtain valid results due to test failures. A total of 378 pregnant women were available for follow-up, while 16 patients were lost to follow-up. Of these 378, 135 pregnant women chose further prenatal diagnosis through amniocentesis, and one case of dysplasia was recalled for postpartum chromosome testing. The incidence rate of congenital chromosomal abnormalities in those who failed the NIPS was 3.97% (15/378), which was higher than that of the chromosomal abnormalities in the common population (1.8%). Among the pregnant women who received prenatal diagnosis, the positive rates of chromosomal abnormalities in the chromosomal microarray analysis/copy number variation sequencing (CMA/CNV-seq) group and in the karyotyping group were 15.28 and 4.76%, respectively.ConclusionPrenatal diagnosis should be strongly recommended in posttest genetic counseling for pregnant women with NIPS failures. Further, high-resolution detection methods should be recommended for additional prenatal diagnoses.

scholarly journals The Value of Non-Invasive Prenatal Testing in the Diagnosis of Birth Defects: Insights from a Large Multicentre Study in Southern China

2021 ◽  
Author(s):  
Meiying Cai ◽  
Na Lin ◽  
Xuemei Chen ◽  
Ying Li ◽  
Min Lin ◽  
...  
Keyword(s):  
Multicentre Study ◽  
Pregnant Women ◽  
Chromosomal Abnormalities ◽  
Southern China ◽  
Prenatal Testing ◽  
Copy Number Variations ◽  
Trisomy 13 ◽  
Detection Rates ◽  
Non Invasive ◽  
Large Multicentre Study

Abstract Non-invasive prenatal testing (NIPT) is a fast, safe, and non-disruptive diagnostic method. At present, few studies have evaluated the screening efficiency of NIPT positive predictive value (PPV) in study subjects. Here, the results of NIPT in pregnant women were retrospectively analysed, and the detection rate, PPV and follow-up data were evaluated to determine its clinical value. A large multicentre study was conducted involving 52,855 pregnant women who received NIPT. Based on gestational age, amniotic fluid or umbilical cord blood were extracted for simultaneous karyotype and chromosome microarray analysis (CMA) in NIPT-positive patients. Among the 52,855 cases, 754 were NIPT-positive, with a positivity rate of 1.4%. Karyotype analysis and/or CMA confirmed 323 cases of chromosomal abnormalities, with a PPV of 45.1%. PPV of Trisomy 21 (T21), Trisomy 18 (T18), Trisomy 13 (T13), sex chromosomal aneuploidies (SCA) and copy number variations (CNV) were 78.9%, 35.3%, 22.2%, 36.9% and 32.9%, respectively. The PPV of T21, T18, and T13 increased with age whereas, the PPV of SCA and CNVs had little correlation with age. The PPV was significantly high in patients with advanced age along with an abnormal ultrasound.NIPT had a high PPV for T21, and a low PPV for T13 and T18, while screening for SCA and CNVs showed clinical significance. However, in case of NIPT screening for SCA and CNVs, simultaneous karyotype and CMA should be performed to increase the detection rates. Interventional prenatal diagnosis is still required in NIPT-positive cases to avoid false positives or unnecessary termination of pregnancy.

scholarly journals Implementation of cell-free DNA-based non-invasive prenatal testing in a National Health Service Regional Genetics Laboratory

2019 ◽  
Vol 101 ◽  
Author(s):  
Fiona S. Togneri ◽  
Mark D. Kilby ◽  
Elizabeth Young ◽  
Samantha Court ◽  
Denise Williams ◽  
...  
Keyword(s):  
National Health Service ◽  
High Risk ◽  
Health Service ◽  
National Health ◽  
Prenatal Testing ◽  
Low Risk ◽  
Trisomy 13 ◽  
Cell Free Dna ◽  
Non Invasive ◽  
Free Dna

Abstract Background Non-invasive prenatal testing (NIPT) for the detection of foetal aneuploidy through analysis of cell-free DNA (cfDNA) in maternal blood is offered routinely by many healthcare providers across the developed world. This testing has recently been recommended for evaluative implementation in the UK National Health Service (NHS) foetal anomaly screening pathway as a contingent screen following an increased risk of trisomy 21, 18 or 13. In preparation for delivering a national service, we have implemented cfDNA-based NIPT in our Regional Genetics Laboratory. Here, we describe our validation and verification processes and initial experiences of the technology prior to rollout of a national screening service. Methods Data are presented from more than 1000 patients (215 retrospective and 840 prospective) from ‘high- and low-risk pregnancies’ with outcome data following birth or confirmatory invasive prenatal sampling. NIPT was by the Illumina Verifi® test. Results Our data confirm a high-fidelity service with a failure rate of ~0.24% and a high sensitivity and specificity for the detection of foetal trisomy 13, 18 and 21. Secondly, the data show that a significant proportion of patients continue their pregnancies without prenatal invasive testing or intervention after receiving a high-risk cfDNA-based result. A total of 46.5% of patients referred to date were referred for reasons other than high screen risk. Ten percent (76/840 clinical service referrals) of patients were referred with ultrasonographic finding of a foetal structural anomaly, and data analysis indicates high- and low-risk scan indications for NIPT. Conclusions NIPT can be successfully implemented into NHS regional genetics laboratories to provide high-quality services. NHS provision of NIPT in patients with high-risk screen results will allow for a reduction of invasive testing and partially improve equality of access to cfDNA-based NIPT in the pregnant population. Patients at low risk for a classic trisomy or with other clinical indications are likely to continue to access cfDNA-based NIPT as a private test.

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