Clinical utility of expanded non-invasive prenatal screening and chromosomal microarray analysis in high-risk pregnancy

Psychometric properties of the Chinese version of the Get Active Questionnaire for Pregnancy and its companion form to assess physical activity readiness

INTRODUCTION

Engaging in physical activity is essential for a healthy pregnancy. A reliable tool is necessary to enhance the assessment and counseling of safe physical activity. This study aimed to translate the original English Get Active Questionnaire for Pregnancy (GAQ-P) and its companion Health Care Provider Consultation Form for Prenatal Physical Activity (cHCP-CF-PPA) into simplified Chinese language and evaluate the psychometric properties in Chinese pregnant women.

METHODS

The Brislin's model of translation was employed to translate the GAQ-P/cHCP-CF-PPA tool. We conducted a cross-sectional study at a tertiary women's hospital in Shanghai, China, enrolling a convenience sample of 325 pregnant women across all trimesters to evaluate the psychometric properties of the GAQ-P/cHCP-CF-PPA. Reliability was assessed through test-retest reliability and inter-rater reliability, while validity was examined using content validity, known-groups validity, and criterion validity. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated using PARmed-X for Pregnancy as the gold standard.

RESULTS

Regarding content validity, the GAQ-P had an average S-CVI/UA of 0.81 (I-CVIs: 0.83-1.0), while the cHCP-CF-PPA exhibited an average S-CVI/UA of 0.87 (I-CVIs: 0.83-1.0). The GAQ-P/cHCP-CF-PPA scores effectively distinguished women recommended for physical activity from those with contraindications. The Spearman's correlations between the GAQ-P/cHCP-CF-PPA and the PARmed-X for Pregnancy were 0.851 for absolute contraindications and 0.847 for relative contraindications. The test-retest reliability score was 0.759 for physical activity contraindications, and 0.953 for inter-rater reliability. The sensitivity of the GAQ-P/cHCP-CF-PPA was determined to be 90.00%, with a specificity of 98.31%. The positive predictive value was 78.26%, while the negative predictive value reached 99.32%.

CONCLUSION

The Chinese version of the GAQ-P/cHCP-CF-PPA is a reliable and valid tool for assessing physical activity readiness in pregnant women.

Has the Era of Individualized Intrauterine Treatment for Congenital Adrenal Hyperplasia Arrived?

BACKGROUND

Congenital adrenal hyperplasia (CAH) is a common metabolic genetic disease. Early diagnosis and intervention are crucial to improve the prognosis. Noninvasive prenatal diagnosis (NIPD) is an early, safe, and accurate method. This study aimed to evaluate the NIPD of CAH while guiding individualized intrauterine treatment.

METHODS

Twenty families with a 25% risk of having a baby with 21-hydroxylase deficiency (21-OHD) were included. Haplotypes were constructed based on targeted sequencing and family linkage analysis. Relative haplotype dosage (RHDO) combined with Bayes factor was used to infer fetal genotypes. Invasive prenatal diagnosis was performed to verify the reliability of NIPD. For affected-female fetuses, intrauterine treatment was applied until delivery.

RESULTS

In 20 families, NIPD successfully identified one female-affected fetus, four male-affected fetuses, nine heterozygotes, and five normal fetuses. The first-pass success rate of NIPD was 90% (18/20), the reporting rate was 95% (19/20), and the accuracy was 100% (19/19). Individualized intrauterine treatment avoided 88.9% (8/9) of unnecessary treatment of unaffected female fetuses. Moreover, no significant virilization was observed in the newborn of CAH16, which underwent intrauterine treatment.

CONCLUSION

NIPD has far-reaching implications for the early treatment and clinical management of pregnancy in families with 21-OHD.

Clinical application of chromosome microarray analysis and karyotyping in prenatal diagnosis in Northwest China

Introduction

Karyotyping and chromosome microarray analysis (CMA) are the two main prenatal diagnostic techniques currently used for genetic testing. We aimed to evaluate the value of chromosomal karyotyping and CMA for different prenatal indications.

Methods

A total of 2084 amniocentesis samples from pregnant women who underwent prenatal diagnosis from 16 to 22 + 6 weeks of gestation between January 2021 and December 2022 were retrospectively collected. The pregnant women were classified according to different prenatal diagnostic indications and underwent CMA and karyotype analysis. Clinical data were collected, and the results of the CMA and karyotype analysis were statistically analyzed to compare the effects of the two diagnostic techniques.

Results

The total detection rate of abnormal chromosomes was significantly higher using CMA than karyotype analysis. The detection rate of abnormal chromosomes using CMA was significantly higher than that using karyotyping for ultrasound abnormalities, high-risk serologic screening, adverse pregnancy history, positive noninvasive prenatal test (NIPT) screening, and ultrasound abnormalities combined with adverse pregnancy history indications. Among the fetuses with inconsistent results between the two testing methods, 144 had an abnormal CMA but a normal karyotype, with the highest percentage of pregnant women with ultrasound abnormalities at 38.89% (56/144). CMA had the highest detection rate for structural abnormalities combined with soft-index abnormalities among all ultrasound abnormalities. The highest detection rate of copy number variants in the group of structural abnormalities in a single system was in the genitourinary system (3/29, 10.34%).

Conclusion

CMA can improve the detection rate of chromosomal abnormalities in patients with ultrasound abnormalities, high-risk serologic screening, adverse maternal history, positive NIPT screening, and ultrasound abnormalities combined with adverse maternal history and can increase the detection rate of chromosomal abnormalities in karyotypic normality by 6.91% (144/2,084), this result is higher than similar studies. However, karyotype analysis remains advantageous over CMA regarding balanced chromosomal rearrangement and detection of low-level chimeras, and the combination of the two methods is more helpful in improving the detection rate of prenatal chromosomal abnormalities.

Accuracy of expanded noninvasive prenatal testing for maternal copy number variations: A comparative study with CNV-seq of maternal lymphocyte DNA

OBJECTIVE

To evaluate the accuracy of expanded noninvasive prenatal testing (NIPT) for maternal copy number variations.

MATERIALS AND METHODS

Expanded NIPT was used to detect CNVs ≥2 Mb at a whole-genome scale. The threshold of maternal deletion was copy numbers (CN) ≤ 1.6, and the threshold of maternal duplication was CN ≥ 2.4.

RESULTS

Of the 5440 pregnant women with successful expanded NIPT results, 28 maternal CNVs ≥2 Mb were detected in 27 pregnant women. Except for five cases reported as test failure, 23 CNVs ≥2 Mb were confirmed among the remaining 22 pregnant women by CNV-seq of maternal lymphocyte DNA. The genomic location, copy numbers and fragment size of maternal CNVs reported by expanded NIPT were consistent with the results of CNV-seq of maternal lymphocyte DNA.

CONCLUSIONS

Maternal CNVs ≥2 Mb can be accurately evaluated according to the CN indicated by expanded NIPT results.

Discordant performances of non-invasive prenatal testing for foetal trisomy 21 screening in subgroups of pregnancies

BACKGROUND

Non-invasive prenatal testing (NIPT) has been widely adopted as an approach for foetal aneuploidy screening. This study was to evaluate the performance of NIPT for foetal T21 detection in subgroups of pregnancies and the correlation between Z-score and discordant positive predictive values (PPVs).

METHODS

We retrospectively reviewed the NIPT results among 22361 pregnancies undergoing combined second-trimester screening (cSTS) previously. Sixty-four cases with positive NIPT results for foetal T21 were validated by invasive prenatal diagnosis.

RESULTS

In pregnancies with cSTS-T21 low-, intermediate-, and high-risk, the PPVs at NIPT were 14.3%, 64.3%, and 86.4%, respectively. Mean Z-scores of positive NIPT cases with cSTS-T21 high- and intermediate-risk were comparable, while were higher than that of cases with pre-test low-risk. Furthermore, PPVs for positive NIPT cases at 3 < Z < 5, 5 ≤ Z < 9, and Z ≥ 9 were 16.7%, 63.2%, and 100.0%, respectively.

CONCLUSIONS

This study suggested that Z-score value of positive cases might be associated with discordant PPVs for T21 screening in subgroups of pregnancies.

A call for public funding of invasive and non-invasive prenatal testing

For decades, prenatal screening and genetic testing strategies were limited, requiring less complex decisions. Recently, however, several new advanced technologies were introduced, including chromosomal microarray analysis (CMA) and non-invasive prenatal screening (NIPS), bringing about the need to choose the most appropriate testing for each pregnancy. A worrisome issue is that opposed to the wide implementation and debates over public funding of NIPS, currently invasive testing is still recommended only in selected pregnancies with increased risk for chromosomal aberrations (according to screening tests or sonographic anomalies). This current decision-making regarding public funding for invasive and screening testing might compromise informed consent and patient's autonomy. In this manuscript, we compare several characteristics of CMA vs. NIPS, namely: the accuracy and the diagnostic scope, the risks for miscarriage and for clinically uncertain findings, the timing for testing, and pretest counselling. We argue that it must be recognized that one size might not fit all, and suggest that both options should be presented to all couples through early genetic counseling, with public funding for the specific selected test.

Prenatal Screening for Microdeletions and Rare Autosomal Aneuploidies

Noninvasive prenatal screening with cell-free DNA is now considered a first-line screening for common aneuploidies. Advancements in existing laboratory techniques now allow to interrogate the entirety of the fetal genome, and many commercial laboratories have expanded their screening panels to include screening for rare autosomal aneuploidies and copy number variants. Here, we review the currently available data on the performance of fetal cell-free DNA to detect rare autosomal aneuploidies and copy number variants that are associated with clinically significant microdeletion and microduplication syndromes and the current position of medical societies on routine screening for these syndromes.

The predictive value of noninvasive prenatal screening for copy number variations: a cohort study and a systematic meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of noninvasive prenatal screening (NIPS) in screening for copy number variations (CNVs).

METHODS

We conducted a systematic review and meta-analysis by combining our study results with those reported in other articles. We retrospectively collected the data of pregnant women with NIPS testing in the Hangzhou Women's Hospital from December 2019 to February 2022. Simultaneously, a systematic search of PubMed, EMBASE, and Web of Science was carried out to identify all relevant peer-reviewed publications. Statistical analysis was performed based on the random-effects model to determine a pooled estimate of the positive predictive value (PPV).

RESULTS

A total of 29 studies involving 2,667 women were included for analysis. The pooled PPV of NIPS in the detection of CNVs was 32.86% (95% confidence interval [24.61-41.64]). Statistical heterogeneity was high, while no significant publication bias was found in this meta-analysis. There were insufficient data to accurately determine sensitivity and specificity, as most studies only performed confirmatory tests on high-risk women.

CONCLUSIONS

The PPV of NIPS in screening for CNVs was approximately 33%. Cautions should be kept in mind for the pretest guidance and subsequent after-test counseling when offering such genome-wide NIPS tests.

A good screening test: not just high sensitivity

Linked article: This Correspondence comments on Maya et al. Click here to view the article.

The predictive value of prenatal cell-free DNA testing for rare autosomal trisomies: a systematic review and meta-analysis

OBJECTIVE

The diagnostic accuracy of cell-free fetal DNA in screening for rare autosomal trisomies is uncertain. We conducted a systematic review and meta-analysis aiming to determine the predictive value of cell-free DNA in screening for rare autosomal trisomies.

DATA SOURCES

PubMed, Embase, and Web of Science were searched from inception to January 2022.

STUDY ELIGIBILITY CRITERIA

All studies that reported on the diagnostic accuracy of cell-free DNA in the detection of rare autosomal trisomies were included. Case series were included if they contained at least 10 cases with diagnostic test results or postnatal genetic testing.

METHODS

Study appraisal was completed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Statistical analysis was performed using random-effects meta-analysis of double-arcsine transformed proportions of confirmed results in the fetus out of the positive tests to obtain a pooled estimate of the positive predictive value.

RESULTS

The search identified 7553 studies, of which 1852 were duplicates. After screening 5701 titles and abstracts, 380 studies proceeded to the full-text screen; 206 articles were retrieved for data extraction, of which another 175 articles were excluded. A total of 31 studies, with a total of 1703 women were included for analysis. The pooled positive predictive value of cell-free DNA for the diagnosis of rare autosomal trisomies was 11.46% (95% confidence interval, 7.80-15.65). Statistical heterogeneity was high (I²=82%). Sensitivity analysis restricted to 5 studies at low risk of bias demonstrated a pooled positive predictive value of 9.13% (95% confidence interval, 2.49-18.76). There were insufficient data to provide accurate ascertainment of sensitivity and specificity because most studies only offered confirmatory tests to women with high-risk results.

CONCLUSION

The positive predictive value of cell-free DNA in diagnosing rare autosomal trisomies is approximately 11%. Clinicians should provide this information when offering cell-free DNA for screening of conditions outside of common autosomal trisomies.

The accuracy of cell-free DNA screening for fetal segmental copy number variants: A systematic review and meta-analysis

BACKGROUND

The performance of cell-free DNA (cfDNA) screening for microscopic copy number variants (CNVs) is unclear.

OBJECTIVES

This was a systematic review and meta-analysis to investigate the sensitivity, specificity and positive predictive value (PPV) of cfDNA screening for CNVs.

SEARCH STRATEGY

Articles published in EMBASE, PubMed or Web of Science before November 2022 were screened for inclusion. This protocol was registered with PROSPERO (23 March 2021, CRD42021250849) prior to initiation.

SELECTION CRITERIA

Articles published in English, detailing diagnostic outcomes for at least 10 high-risk CNV results with cfDNA were considered for inclusion.

DATA COLLECTION AND ANALYSIS

The PPV was calculated and pooled with random-effects models for double-arcsine transformed proportions, using cases with diagnostic confirmation. Overall sensitivity, specificity and a summary receiver-operating characteristics (ROC) curve were calculated using bivariate models. The risk of bias was assessed using QUADAS-2.

MAIN RESULTS

In all, 63 articles were included in the final analysis, detailing 1 591 459 cfDNA results. The pooled PPV was 37.5% (95% confidence interval [CI] 30.6-44.8), with substantial statistical heterogeneity (I²  = 93.9%). Bivariate meta-analysis estimated sensitivity and specificity to be 77.4% (95% CI 65.7-86.0) and 99.4% (95% CI 98.0-99.8), respectively, with an area under the summary ROC curve of 0.947 (95% CI 0.776-0.984).

CONCLUSIONS

Approximately one-third of women who screen high-risk for CNVs with cfDNA will have an affected fetus. This value is of importance for screening counselling.

Genome-Wide Cell-Free DNA Test for Fetal Chromosomal Abnormalities and Variants: Unrestricted Versus Restricted Reporting

This study aimed to compare the screening performance of genome-wide cfDNA testing for chromosomal abnormalities between two periods where additional findings were reported and not reported. Data were obtained from consecutive pregnant women with a singleton pregnancy at ≥10 weeks who requested cfDNA testing during 2015–2019. The performance of screening of the cfDNA test was determined by calculating the concordance rate, detection rate, and false-positive rate. Data from 3981 women were included. The no-result rates were similar between the two reporting periods (2.04% vs. 2.08%). Concordance rates for trisomy 21 and 18 were 100% and 100%, respectively. There were two cases tested high risk for trisomy 13, with a concordance rate of 0%. In total, 12 cases were high risk for any sex chromosome aneuploidy with an overall concordance of 75%, and 15 cases tested high risk for any rare autosomal trisomy, with a 13.3% concordance rate. The detection rates for trisomy 21 and 18 were 100% and 100%, respectively. For any SCA, the detection rate was 90%. For the two reporting periods, the combined false-positive rates were 0.93% and 0.17%, which were significantly different (p = 0.002). Restricting the reporting of additional findings from genome-wide cfDNA analysis has reduced the false-positive rate but without a reduction in the no-result rate.

Clinical experience of noninvasive prenatal testing for rare chromosome abnormalities in singleton pregnancies

Objectives: The study aimed to investigate the clinical use of noninvasive prenatal testing (NIPT) for common fetal aneuploidies as a prenatal screening tool for the detection of rare chromosomal abnormalities (RCAs). Methods: Gravidas with positive NIPT results for RCAs who subsequently underwent amniocentesis for a single nucleotide polymorphism array (SNP array) were recruited. The degrees of concordance between the NIPT and SNP array were classified into full concordance, partial concordance, and discordance. The positive predictive value (PPV) was used to evaluate the performance of NIPT. Results: The screen-positivity rate of NIPT for RCAs was 0.5% (842/158,824). Of the 528 gravidas who underwent amniocentesis, 29.2% (154/528) were confirmed to have positive prenatal SNP array results. PPVs for rare autosomal trisomies (RATs) and segmental imbalances were 6.1% (7/115) and 21.1% (87/413), respectively. Regions of homozygosity/uniparental disomy (ROH/UPD) were identified in 9.5% (50/528) of gravidas. The PPV for clinically significant findings was 8.0% (42/528), including 7 cases with mosaic RATs, 30 with pathogenic/likely pathogenic copy number variants, and 5 with imprinting disorders. Conclusion: NIPT for common fetal aneuploidies yielded low PPVs for RATs, moderate PPVs for segmental imbalances, and incidental findings for ROH/UPD. Due to the low PPV for clinically significant findings, NIPT for common fetal aneuploidies need to be noticed for RCAs.

Positive predictive value estimates for noninvasive prenatal testing from data of a prenatal diagnosis laboratory and literature review

Objective

Since 2011, noninvasive prenatal testing (NIPT) has undergone rapid expansion, with both utilization and coverage. However, conclusive data regarding the clinical validity and utility of this testing tool are lacking. Thus, there is a continued need to educate clinicians and patients about the current benefits and limitations in order to inform pre- and post-test counseling, pre/perinatal decision making, and medical risk assessment/management.

Methods

This retrospective study included women referred for invasive prenatal diagnosis to confirm positive NIPT results between January 2017 and December 2020. Prenatal diagnosis testing, including karyotyping, chromosomal microarray analysis (CMA) were performed. Positive predictive values (PPVs) were calculated.

Results

In total, 468 women were recruited. The PPVs for trisomies 21, 18, and 13 were 86.1%, 57.8%, and 25.0%, respectively. The PPVs for rare chromosomal abnormalities (RCAs) and copy number variants (CNVs) were 17.0% and 40.4%, respectively. The detection of sex chromosomal aneuploidies (SCAs) had a PPV of 20% for monosomy X, 23.5% for 47,XXX, 68.8% for 47,XXY, and 62.5% for 47,XYY. The high-risk groups had a significant increase in the number of true positive cases compared to the low- and moderate-risk groups.

Conclusions

T13, monosomy X, and RCA were associated with lower PPVs. The improvement of cell-free fetal DNA screening technology and continued monitoring of its performance are important.

Prenatal Diagnosis Using Chromosomal Microarray Analysis in High-Risk Pregnancies

Background: To assess the value of chromosomal microarray analysis (CMA) during the prenatal diagnosis of high-risk pregnancies. Methods: Between January 2016 and November 2021, we included 178 chorionic villi and 859 amniocentesis samples from consecutive cases at a multiple tertiary hospital. Each of these high-risk singleton pregnancies had at least one of the following indications: (1) advanced maternal age (AMA; ≥35 years; 546, 52.7%); (2) fetal structural abnormality on ultrasound (197, 19.0%); (3) high-risk first- or second-trimester Down syndrome screen (189, 18.2%), including increased nuchal translucency (≥3.5 mm; 90, 8.7%); or (4) previous pregnancy, child, or family history (105, 10.1%) affected by chromosomal abnormality or genetic disorder. Both G-banding karyotype analysis and CMA were performed. DNA was extracted directly and examined with oligonucleotide array-based comparative genomic hybridization. Results: Aneuploidies were detected by both G-banding karyotyping and CMA in 42/1037 (4.05%) cases. Among the 979 cases with normal karyotypes, 110 (10.6%) cases had copy number variants (CNVs) in CMA, including 30 (2.9%) cases with reported pathogenic and likely pathogenic CNVs ≥ 400 kb, 37 (3.6%) with nonreported VOUS, benign, or likely benign CNVs ≥ 400 kb, and 43 (4.1%) with nonreported CNVs < 400 kb. Of the 58 (5.6%) cases with aneuploidy rearrangements, 42 (4.1%) were diagnosed by both G-banding karyotyping and CMA; four inversions, six balanced translocations, and six low mosaic rates were not detected with CMA. Conclusions: CMA is an effective first step for the prenatal diagnosis of high-risk pregnancies with fetal structural anomalies found in ultrasonography or upon positive findings.

Is Cell-free fetal DNA testing a safe option for women in a high-risk population after combined first-trimester testing?

OBJECTIVES

Our study aimed to examine the relevance of cell-free fetal DNA (cfDNA) testing on the screening of chromosomal defects and the issue of pregnancies in patients with a risk over 1:50 after the first-trimester combined test.

METHODS

This is a retrospective monocentric study. We included all consecutive patients with a singleton pregnancy between January 2015 and December 2020 attending our fetal medicine centre because the estimated risk for trisomy 21 after the first-trimester combined screening was over 1:50. The patients could either choose to have invasive testing or cell-free DNA testing. We collected data about the patient, the tests results (cfDNA, karyotype) and the pregnancy outcome (born alive, medical termination, miscarriage or intrauterine fetal death).

RESULTS

We included 98 patients with an estimated risk for trisomy 21 over 1:50. We found a total of 14 major chromosomal abnormalities (14/98; 14.3%), of which: thirteen trisomies 21 and one triploidy 69, XXY. A cfDNA testing was chosen by 34 (34/98; 34.7%) patients. Among the pathological results of invasive testing, 5 (5/64; 7.8%) couldn't be targeted by cfDNA testing. Two of them were placental mosaicism, one a triploidy 69, XXY, and two defects inherited from a parent and considered benign. There was no miscarriage linked to an invasive test in the population study.

CONCLUSION

In our monocentric cohort, a third of the patients choose cfDNA in a case of a risk over 1:50 after combined testing. Even if this cohort is too small to draw definitive conclusions, cfDNA could be safe in a high-risk population after combined testing. None of the chromosomal abnormalities found at the karyotype and non-detectable by cfDNA was a loss of information that impacted pregnancy follow-up. Further study could explore the input of Genome-Wide cfDNA and chromosomal micro-array in this population.

Mosaicism for copy number variations in the placenta is even more difficult to interpret than mosaicism for whole chromosome aneuploidy

OBJECTIVE

To compare mosaicisms in prenatal chorionic villus samples (CVSs) with corresponding postpartum placental samples.

METHOD

We collected placentas from 15 consecutive cases of mosaicism detected in CVSs and obtained five standardized samples on each placenta after delivery. All pre- and postnatal placental samples were uncultured and analyzed by high-resolution chromosomal microarray.

RESULTS

Ten cases of mosaicism for whole chromosome aneuploidy (mWC) and five cases with mosaicism for (sub)chromosomal copy number variations (mCNVs) were included. In 5/10 mWC cases and in 4/5 mCNV cases the prenatally detected aberration was confirmed in the postpartum placenta. Three postpartum placentas revealed various complex aberrations differing from the prenatal results: (1) mosaicisms for different deletions/duplications on 9p and 9q in all samples (prenatal: mosaic 5.3 Mb duplication on 9p24), (2) different regions with deletions/duplications/loss of heterozygosity on 1p in all samples (prenatal: mosaic 2.3 Mb 1p36 duplication), and (3) mosaicism for a duplication on 5q and a deletion on 6p in one out of five samples (prenatal: mosaic trisomy 7).

CONCLUSION

CNVs constitute a complex subgroup in placental mosaicism. Counseling of these couples after chorionic villus sampling should not focus on the specific CNV involved, but on the nature of mosaicism and the option of amniocentesis and ultrasound.

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

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.

Clinical Significance of Non-Invasive Prenatal Screening for Trisomy 7: Cohort Study and Literature Review

Trisomy 7 is the most frequently observed type of rare autosomal trisomies in genome-wide non-invasive prenatal screening (NIPS). Currently, the clinical significance of trisomy 7 NIPS-positive results is still unknown. We reviewed two independent cohorts from two laboratories where similar NIPS metrics were applied. A total of 70,441 singleton cases who underwent genome-wide NIPS were analyzed, among which 39 pregnancies were positive for trisomy 7, yielding a screen-positive rate of 0.055% (39/70,441). There were 28 cases with invasive testing results available; the positive predictive value (PPV) was 3.6% (1/28). We then searched the published NIPS studies to generate a large cohort of 437,873 pregnancies and identified 247 cases (0.056%) that were screened positive for trisomy 7. The overall PPV was 3.4% (4/118) in the combined data. The presence of uniparental disomy 7 was not detected in the NIPS trisomy 7-positive pregnancies with normal fetal karyotype. Among the 85 cases with pregnancy outcome available in combined data, 88.2% were normal live births, 14.1% had intrauterine growth restriction, preterm birth or low birth weight, 3.5% presented with ultrasound abnormality, and no fetal loss was observed. Our data provide valuable information for counseling and management of trisomy 7-positive NIPS pregnancies.

Next-generation sequencing: a follow-up of 36,913 singleton pregnancies with noninvasive prenatal testing in central China

PURPOSE

To evaluate the noninvasive prenatal testing (NIPT) results of 36,913 cases in Jiangxi province of central China and explore its application value in prenatal screening and diagnosis.

METHODS

This retrospective analysis included 36,913 singleton pregnant women who underwent NIPT because of moderate-/high-risk pregnancy or voluntary requirements between January 2017 and December 2019 in our hospital. Chromosomal abnormalities such as trisomies 21, 18, and 13 (T21, T18, T13) and sex chromosome aneuploidies (SCAs) were judged by standard Z-score analysis. Positive NIPT results were confirmed by amniocentesis and karyotyping. Pregnancy outcomes were followed up via telephone interview.

RESULTS

A total of 1.01% (371/36,913) positive cases were detected by NIPT, comprising 137, 46, 31, and 157 cases of T21, T18, T13, and SCAs, respectively. A total of 116 of T21, 27 of T18, 13 of T13, and 51 of SCAs were confirmed to be true positive; all normal cases that had been followed up were verified to be true negative. The NIPT sensitivity in T21, T18, T13, and SCAs was 100.00% individually, whereas the specificity was 99.94% (36,488/36,509), 99.95% (36,579/36,598), 99.95% (36,594/36,612), and 99.72% (36,472/36,574), respectively. Furthermore, the negative predictive values of T21, T18, T13, and SCAs were all 100%, while the positive predictive values were 84.67%, 58.70%, 41.94%, and 33.33%, respectively.

CONCLUSION

NIPT is highly sensitive and has a low false positive rate in testing clinically significant fetal aneuploidies of general reproductive women. However, this technique cannot substitute for amniocentesis and karyotyping, and detailed genetic counseling is also essential for the high-risk group of NIPT.