Noninvasive prenatal screening or advanced diagnostic testing: caveat emptor

Correlation between maternal serum biomarkers and the risk of fetal chromosome copy number variants: a single-center retrospective study

OBJECTIVE

To explore the association between the concentration of maternal serum biomarkers and the risk of fetal carrying chromosome copy number variants (CNVs).

METHODS

Pregnant women identified as high risk in the second-trimester serological triple screening and underwent traditional amniotic fluid karyotype analysis, along with comparative genomic hybridization array (aCGH)/copy number variation sequencing (CNV-seq), were included in the study. We divided the concentration of serum biomarkers, free beta-human chorionic gonadotropin (fβ-hCG), alpha fetoprotein (AFP) and unconjugated estriol (uE3), into three levels: abnormally low, normal and abnormally high. The prevalence of abnormally low, normal and abnormally high serum fβ-hCG, AFP and uE3 levels in pregnant women with aberrant aCGH/CNV-seq results and normal controls was calculated.

RESULTS

Among the 2877 cases with high risk in the second-trimester serological triple screening, there were 98 chromosome abnormalities revealed by karyotype analysis, while 209 abnormalities were detected by aCGH/CNVseq (P＜0.001) . The carrying rate of aberrant CNVs increased significantly when the maternal serum uE3 level was less than 0.4 multiple of median (MoM) of corresponding gestational weeks compared to normal controls, while the carrying rate of aberrant CNVs decreased significantly when the maternal serum fβ-hCG level was greater than 2.5 MoM compared to normal controls. No significant difference was found in the AFP group.

CONCLUSION

Low serum uE3 level (<0.4 MoM) was associated with an increased risk of aberrant CNVs.

Etiology and Ontogeny of Cerebral Palsy: Implications for Practice and Research

Cerebral palsy (CP) has been recognized as a group of neurologic disorders with varying etiologies and ontogenies. While a percentage of CP cases arises during labor, the expanded use of electronic fetal monitoring (EFM) to include prevention of CP has resulted in decades of vastly increased interventions that have not significantly reduced the incidence of CP for infants born at term in the USA. Litigation alleging that poor obstetrical practice caused CP in most of these affected children has led to contentious arguments regarding the actual etiologies of this condition and often resulted in substantial monetary awards for plaintiffs. Recent advances in genetic testing using whole exome sequencing have revealed that at least one-third of CP cases in term infants are genetic in origin and therefore not labor-related. Here, we will present and discuss previous attempts to sort out contributing etiologies and ontogenies of CP, and how these newer diagnostic techniques are rapidly improving our ability to better detect and understand such cases. In light of these developments, we present our vision for an overarching spectrum for proper categorization of CP cases into that the following groups: (1) those begun at conception from genetic causes (nonpreventable); (2) those stemming from adverse antenatal/pre-labor events (possibly preventable with heightened antepartum assessment); (3) Those arising from intrapartum events (potentially preventable by earlier interventions); (4) Those occurring shortly after birth (possibly preventable with closer neonatal monitoring); (5) Those that appear later in the postnatal period from non-labor-related causes such as untreated infections or postnatal intracranial hemorrhages.

Current controversies in prenatal diagnosis: Noninvasive prenatal testing should replace other screening strategies for fetal trisomies 13, 18, 21

This is a written summary of the oral debate presented at the International Society for Prenatal Diagnosis annual conference in Edinburgh in 2023. The topic under debate is whether noninvasive prenatal testing (NIPT) using cell-free fetal DNA should replace other screening strategies for the detection of fetal trisomies 13, 18, 21. There is no disagreement that NIPT is far more sensitive and has better positive predictive values for identifying trisomies 13, 18, and 21 than traditional screening approaches using biochemical markers and measurement of nuchal translucency. The major issue lies in the potential adverse consequences associated with abandoning traditional screening methods. The source of disagreement stems primarily from whether you consider the role of ultrasound in the context of screening to be strictly for nuchal translucency measurement or whether it should be combined with a fetal anatomy scan. The debate featured two experts who presented evidence in favor of each argument.

A rapid PCR-free next-generation sequencing method for comprehensive diagnosis of chromosome disease syndromes in prenatal samples

The aim of this study is to investigate the application performance of rapid copy number variation sequencing (rCNV-seq) technology for the detection of chromosomal abnormalities during prenatal diagnosis. Samples were collected from 424 pregnant women who were at high-risk for noninvasive prenatal screening in Kunming Maternal and Child Care Hospital from January 2018 to May 2022. rCNV-seq technique was used to detect fetal chromosome abnormalities and compare the results with that of chromosomal karyotype analysis. The Result showed that 330 (77.83%, 330/424) cases indicated chromosomal abnormalities among 424 high-risk pregnant women who underwent rCNV-seq. Moreover, 94 (22.17%, 94/424) cases were discovered to have copy number variations. Among the 330 fetuses with chromosomal abnormalities, common autosomal aneuploidy was observed in 203 cases (47.87%, 203/424) and sex chromosome aneuploidy was observed in 91 cases (21.46%, 91/424). Moreover, the abnormalities in multiple chromosomes were discovered in 33 cases (7.78%, 33/424), and the rare autosomal aneuploidy was observed in 3 cases (0.71%, 3/424). There were 63 fetuses (14.86%, 63/424) with pathogenic CNVs among the 94 fetuses with variable copy numbers. Of the 245 pregnant women who voluntarily selected G-band karyotyping, 1 fetus with copy number variation had normal karyotype results, and the remaining women were consistent with rCNV-seq. Our study revealed that rCNV-seq has higher accuracy in detecting common trisomy and can also detect chromosomal microdeletions or microduplications that cannot be detected by G-banding karyotype analysis. There is no effective treatment for chromosomal diseases, so it is particularly important to prevent chromosomal diseases through genetic counseling and prenatal diagnosis of chromosomal diseases.

Clinical value of positive CNVs results by NIPT without fetal ultrasonography-identified structural anomalies

OBJECTIVE

To evaluate the clinical value of positive copy number variations (CNVs) results by non-invasive prenatal testing (NIPT) without fetal ultrasonography-identified structural anomalies, especially with several known CNVs results.

METHODS

A total of 135,981 results of NIPT performed between April 1, 2017, and March 31, 2020, enrolled in the free NIPT service program implemented by the local government were retrospectively analyzed. Of these, 87 cases with positive NIPT screens for CNVs and no fetal ultrasonography-identified anomalies were recalled and provided genetic counseling. After obtaining full informed consent, these cases were provided invasive prenatal diagnosis by karyotyping and chromosomal microarray analysis (CMA)/copy number variation sequencing (CNV-seq) with follow-up. One case was lost, while 86 cases were successfully followed up.

RESULTS

A total of 44 (50.6%) cases underwent invasive prenatal diagnosis, of which six cases were detected with abnormal karyotype. CMA/CNV-Seq revealed 11 fetuses with positive results for CNVs, among whom eight were consistent with NIPT results, two were partially consistent, one was inconsistent, and positive predictive value (PPV) was 22.7% (10/44). For known CNVs, PPVs were 20% (15q11.2-q13 microdeletion) and 33.3% (5p end deletions). Among 11 pregnant women with positive prenatal diagnosis, seven were confirmed to have pathogenic CNVs in their fetuses; four had CNVs of unknown clinical significance.

CONCLUSIONS

Even in pregnancies without ultrasonography-identified anomalies, a positive NIPT screen for CNVs must be interpreted with caution and validated by additional diagnostic study.

Noninvasive prenatal screening with conventional sequencing depth to screen fetal copy number variants: A retrospective study of 19 144 pregnant women

AIM

To investigate the detectability of noninvasive prenatal screening (NIPS) with conventional sequencing depth to detect fetal copy number variants.

METHODS

We performed a retrospective study in a total of 19 144 pregnant women. Their cell-free plasma DNA were assessed for trisomy 21, trisomy 18, trisomy 13, sex chromosome aneuploidies, and genome-wide copy number variants by NIPS at conventional sequencing depth.

RESULTS

Three hundred seventy-four cases (2.0%, 374/19 144) with abnormal results were detected, which including 84 cases (0.4%, 84/19 144) with high risk of trisomy 21, 18, and 13, 90 cases (0.5%, 90/19 144) with high risk of sex chromosome abnormalities (SCA), and 44 cases (0.2%, 44/19 144) with high risk of other chromosome aneuploidies. One hundred fifty-six cases (0.8%, 156/19 144) with high risk of copy number variations (CNVs) were also detected. In following prenatal diagnosis, composite positive predictive value (PPV) of trisomy 21, 18, and 13 was 69.6% (48/69). The PPV of SCAs was 37.3% (19/51). And the PPVs for CNVs was detected as 51.0% (<5 Mb), 71.4% (5 Mb ≤ CNV ≤10 Mb), 56.5% (>10 Mb). Finally, a follow-up about the pregnancy outcomes were conducted for all available cases.

CONCLUSIONS

NIPS yielded high PPVs for trisomy 21, 18, and 13 aneuploidies and moderate PPVs for SCAs and CNVs. The screening effectiveness was closely related to the size of CNV fragments. Larger CNVs, especially larger than 5 Mb, could be detected more accurately by NIPS in our analytic technique. Meanwhile, diagnostic confirmation by microarray analysis was highly recommended.

Evaluation of the clinical effects of non-invasive prenatal screening for diseases associated with aneuploidy and copy number variation

BACKGROUND

To explore and compare the clinical effects of high-resolution non-invasive prenatal screening (NIPS-Plus) for common/uncommon chromosomal aneuploidy and microdeletion/microduplication syndromes (MMS).

METHODS

The current prospective study included a total of 25,380 pregnant women who performed NIPS-Plus, and amniocentesis was performed on women with MMS with the screening results to diagnose patients with suspected MMS.

RESULTS

There were 415 samples with positive results for NIPS-Plus, included 275 with aneuploidy and 140 with MMS. After diagnosis by amniocentesis, 188 cases were confirmed as true positive, included46 cases of T21, 9 cases of T18, 1 case of T13, 34 cases of SCA, 41 cases of other chromosomal euploidy and 57 cases of MMS. In addition, no false negative cases were found, MMS was classified with 5 Mb with the cutoff value, and the PPV of different fragment size was counted, respectively.

CONCLUSION

We found that the corresponding PPV was 44.66% with the fragment of copy number variation (CNV) being less than or equal to 5 Mb, and when it was greater than 5 Mb, the PPV was 29.73%, which suggested that NIPS-Plus was more suitable for screening the PPV of small fragment abnormalities. NIPS-Plus has a good application effect in routine aneuploidy screening and had the best detection effect for T21; moreover, it performed well in screening of MMS and had better detection effect on MMS with CNV fragment length less than 5 Mb. Based on the current results, we suggested that NIPS-Plus should be used as a comprehensive elementary prenatal screening method for all pregnant women, but for MMS caused by abnormal large fragment CNV, the detection method and efficiency still need to be improved.

Defining the scope of extended NIPS in Western China: evidence from a large cohort of fetuses with normal ultrasound scans

BACKGROUND

Standard noninvasive prenatal screening(NIPS) is an accurate and reliable method to screen for common chromosome aneuploidies, such as trisomy 21, 18 and 13. Extended NIPS has been used in clinic for not only aneuploidies but also copy number variants(CNVs). Here we aim to define the range of chromosomal abnormalities that should be able to identify by NIPS in order to be an efficient extended screening test for chromosomal abnormalities.

METHODS

A prospective study was conducted, involving pregnant women without fetal sonographic structural abnormalities who underwent amniocentesis. Prenatal samples were analyzed using copy number variation sequencing(CNV-seq) to identify fetal chromosomal abnormalities.

RESULTS

Of 28,469 pregnancies included 1,022 (3.59%) were identified with clinically significant fetal chromosome abnormalities, including 587 aneuploidies (2.06%) and 435 (1.53%) pathogenic (P) / likely pathogenic (LP) CNVs. P/LP CNVs were found in all chromosomes, but the distribution was not uniform. Among them, P/LP CNVs in chromosomes 16, 22, and X exhibited the highest frequencies. In addition, P/LP CNVs were most common on distal ends of the chromosomes and in low copy repeat regions. Recurrent microdeletion/microduplication syndromes (MMS) accounted for 40.69% of total P/LP CNVs. The size of most P/LP CNVs (77.47%) was < 3 Mb.

CONCLUSIONS

In addition to aneuploidies, the scope of extended NIPS should include the currently known P/LP CNVs, especially the regions with recurrent MMS loci, distal ends of the chromosomes, and low copy repeat regions. To be effective detection should include CNVs of < 3 Mb. Meanwhile, sufficient preclinical validation is still needed to ensure the clinical effect of extended NIPS.

Fetal hyperechoic kidney cohort study and a meta-analysis

Objective: To investigate the positive rate of chromosomal and monogenic etiologies and pregnancy outcomes in fetuses with hyperechoic kidney, and to provide more information for genetic counseling and prognosis evaluation. Methods: We performed a retrospective analysis of 25 cases of hyperechoic kidney diagnosed prenatal in the Second Affiliated Hospital of Harbin Medical University and Harbin Red Cross Central Hospital (January 2017-December 2022). Furthermore, we conducted a meta-analysis of a series of hyperechoic kidneys (HEK) in the literature to assess the incidence of chromosomal and monogenic etiologies, mortality, and pooled odds ratio (OR) estimates of the association between the incidence of these outcomes and other associated ultrasound abnormalities. Results: 25 fetuses of HEK were enrolled in the cohort study, including 14 with isolated hyperechoic kidney (IHK) and 11 with non-isolated hyperechoic kidney (NIHK). Chromosomal aneuploidies were detected in 4 of 20 patients (20%). The detection rate of pathogenic or suspected pathogenic copy number variations (CNVs) was 29% (4/14) for IHK and 37% (4/11) for NIHK. Whole exome sequencing (WES) was performed in 5 fetuses, and pathogenic genes were detected in all of them. The rate of termination of pregnancy was 56% in HEK. 21 studies including 1,178 fetuses were included in the meta-analysis. No case of abnormal chromosome karyotype or (intrauterine death)IUD was reported in fetuses with IHK. In contrast, the positive rate of karyotype in NIHK was 22% and that in HEK was 20%, with the ORs of 0.28 (95% CI 0.16-0.51) and 0.25, (95% CI 0.14-0.44), respectively. The positive rate of (chromosome microarray analysis) CMA in IHK was 59% and that in NIHK was 32%, with the ORs of 1.46 (95% CI 1.33-1.62) and 0.48 (95% CI, 0.28-0.85), respectively. The positive rate of monogenic etiologies in IHK was 31%, with the OR of 0.80 (95% CI 0.25-2.63). In IHK, the termination rate was 21% and neonatal mortality was 13%, with the ORs of 0.26 (95% CI, 0.17-0.40), 1.72 (95% CI, 1.59-1.86), and that in NIHK was 63%, 0.15 (95% CI, 0.10-0.24); 11%, 0.12 (95% CI, 0.06-0.26), respectively. The intrauterine mortality in NIHK group was 2%, with the OR of 0.02 (95% CI, 0.01-0.05). HNF1B variant has the highest incidence (26%) in IHK. Conclusion: The positive rate of karyotype was 20% in HEK and 22% in NIHK. The positive rate of CMA was 32% in NIHK and 59% in IHK. The positive rate of IHK monogenic etiologies was 31%. HNF1B gene variation is the most common cause of IHK. The overall fetal mortality rate of NIHK is significantly higher than that of IHK. The amount of amniotic fluid, kidney size and the degree of corticomedullary differentiation have a great impact on the prognosis, these indicators should be taken into consideration to guide clinical consultation and decision-making.

The Effect of Resolution Level and Targeted Design in the Diagnostic Performance of Prenatal Chromosomal Microarray Analysis

INTRODUCTION

This study was performed to assess the optimal resolution for prenatal testing by array comparative genomic hybridization (aCGH), aiming to balance between maximum diagnostic yield and minimal detection of variants of uncertain significance (VOUS).

METHODS

This was a prospective study using data of 2,336 fetuses that underwent invasive prenatal diagnosis, and the samples were analyzed by aCGH. In total, six different aCGH platforms were studied; four different resolutions (0.18 Mb, 0.5 Mb, 1 Mb, and 2 Mb) and two platform designs (whole-genome [WG] and targeted). The results of these designs were compared based on their diagnostic yield and VOUS rate. The performance of the different designs was further analyzed according to indication for invasive testing.

RESULTS

The diagnostic yield of copy number variants increased with increasing level of analysis. The detection rates of clinically significant chromosomal abnormalities were almost the same across our targeted array designs; 7.2% with 0.18 Mb backbone/0.05 Mb versus 7.1% with 0.5 Mb backbone/0.05 Mb (p >0.05). However, a significant difference in the rate of VOUS was observed; 9.4% with 0.18 Mb backbone/0.05 Mb versus 6% with 0.5 Mb backbone/0.05 Mb (p <0.001). After analyzing the results across different indications for testing, we found that the application of non-targeted platform designs and lower levels of resolution analysis (such as 1 Mb WG or 0.5 MbL/1 MbG WG) would offer similar diagnostic yield in most cases with major congenital anomalies, with lower VOUS rates. However, the sample size for many indication groups was too small to extract robust associations.

CONCLUSION

It appears that the targeted array platform with 0.5 Mb backbone resolution and 0.05 Mb on targeted gene-rich regions is optimal for routine chromosomal microarray analysis use in prenatal diagnosis. It may be beneficial to individualize the minimum resolution in specific referral indications as the indications for invasive prenatal testing may be quite heterogeneous.

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.

Resistance to Change

Advances in medical technology do not follow a smooth process and are highly variable. Implementation can occasionally be rapid, but often faces varying degrees of resistance resulting at the very least in delayed implementation. Using qualitative comparative analysis, we have evaluated numerous technological advances from the perspective of how they were introduced, implemented, and opposed. Resistance varies from benign - often happening because of inertia or lack of resources to more active forms, including outright opposition using both appropriate and inappropriate methods to resist/delay changes in care. Today, even public health has become politicized, having nothing to do with the underlying science, but having catastrophic results. Two other corroding influences are marketing pressure from the private sector and vested interests in favor of one outcome or another. This also applies to governmental agencies. There are a number of ways in which papers have been buried including putting the thumb on the scale where reviewers can sabotage new ideas. Unless we learn to harness new technologies earlier in their life course and understand how to maneuver around the pillars of obstruction to their implementation, we will not be able to provide medical care at the forefront of technological capabilities.

Improving the interpretation of electronic fetal monitoring: the fetal reserve index

Electronic fetal monitoring, particularly in the form of cardiotocography, forms the centerpiece of labor management. Initially successfully designed for stillbirth prevention, there was hope to also include prediction and prevention of fetal acidosis and its sequelae. With the routine use of electronic fetal monitoring, the cesarean delivery rate increased from <5% in the 1970s to >30% at present. Most at-risk cases produced healthy babies, resulting in part from considerable confusion as to the differences between diagnostic and screening tests. Electronic fetal monitoring is clearly a screening test. Multiple attempts have aimed at enhancing its ability to accurately distinguish babies at risk of in utero injury from those who are not and to do this in a timely manner so that appropriate intervention can be performed. Even key electronic fetal monitoring opinion leaders admit that this goal has yet to be achieved. Our group has developed a modified approach called the "Fetal Reserve Index" that contextualizes the findings of electronic fetal monitoring by formally including the presence of maternal, fetal, and obstetrical risk factors and increased uterine contraction frequencies and breaking up the tracing into 4 quantifiable components (heart rate, variability, decelerations, and accelerations). The result is a quantitative 8-point metric, with each variable being weighted equally in version 1.0. In multiple previously published refereed papers, we have shown that in head-to-head studies comparing the fetal reserve index with the American College of Obstetricians and Gynecologists' fetal heart rate categories, the fetal reserve index more accurately identifies babies born with cerebral palsy and could also reduce the rates of emergency cesarean delivery and vaginal operative deliveries. We found that the fetal reserve index scores and fetal pH and base excess actually begin to fall earlier in the first stage of labor than was commonly appreciated, and the fetal reserve index provides a good surrogate for pH and base excess values. Finally, the last fetal reserve index score before delivery combined with early analysis of neonatal heart rate and acid/base balance shows that the period of risk for neonatal neurologic impairment can continue for the first 30 minutes of life and requires much closer neonatal observation than is currently being done.

Prenatal Diagnosis of Uniparental Disomy in Cases of Rare Autosomal Trisomies Detected Using Noninvasive Prenatal Test: A Case of Prader-Willi Syndrome

Rare autosomal trisomies (RATs) other than common aneuploidies can be detected using noninvasive prenatal testing (NIPT). However, conventional karyotyping is insufficient for evaluating diploid fetuses with uniparental disomy (UPD) due to trisomy rescue. Using the diagnostic process for Prader-Willi syndrome (PWS), we aim to describe the need for additional prenatal diagnostic testing for confirming UPD in fetuses diagnosed with RATs via NIPT and its clinical implications. NIPT was performed using the massively parallel sequencing (MPS) method, and all pregnant women with RATs underwent amniocentesis. After confirming the normal karyotype, short tandem repeat (STR) analysis, methylation-specific PCR (MS-PCR), and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) were performed to detect UPD. Overall, six cases were diagnosed with RATs. There was a suspicion of trisomies of chromosomes 7, 8, and 15 in two cases each. However, these cases were confirmed to have a normal karyotype using amniocentesis. In one of six cases, PWS caused by maternal UPD 15 was diagnosed using MS-PCR and MS-MLPA. We propose that in cases where RAT is detected by NIPT, UPD should be considered following trisomy rescue. Even if amniocentesis confirms a normal karyotype, UPD testing (such as MS-PCR and MS-MLPA) should be recommended for accurate assessment, as an accurate diagnosis can lead to appropriate genetic counseling and improved overall pregnancy management.

Comparison of the combined use of CNV-seq and karyotyping or QF-PCR in prenatal diagnosis: a retrospective study

To elevate the accuracy of diagnostic results, CNV-seq is usually performed simultaneously with karyotyping or QF-PCR. Although several studies have investigated the performance of the combined use of CNV-seq with karyotyping or QF-PCR, there have been no reports focusing on the comparison of these 2 diagnostic strategies. In our study, 2507 pregnant women were included to investigate these 2 strategies. The detection rates of foetal genetic abnormalities and turnaround time were compared between these 2 groups. Moreover, the detection rates of foetal genetic abnormalities in different indications were analyzed. Our results unveiled that the detection rates of numerical chromosomal abnormalities were nearly the same in these 2 groups. In addition to numerical chromosomal abnormalities, 39 balanced karyotypic changes and chromosome polymorphisms were detected via the combined use of karyotyping and CNV-seq. Further investigation revealed that the vast majority of these karyotypic changes were inherited from parents. Compared with the karyotyping group, the combination of QF-PCR and CNV-seq reduced the reporting time from 31.593 ± 4.944 days to 11.460 ± 4.894 days. Meanwhile, NIPT, maternal serum screening and ultrasound scan significantly improved the detection of foetal genetic abnormalities. In conclusion, our results revealed that parental karyotyping is a useful supplementary method for CNV-seq and systematic prenatal examinations improved the detection of foetal genetic defects.

Performance of expanded non-invasive prenatal testing for fetal aneuploidies and copy number variations: A prospective study from a single center in Jiangxi province, China

To evaluate the performance of expanded non-invasive prenatal testing (expanded noninvasive prenatal testing, NIPT-Plus) in screening for fetal chromosomal abnormalities includes aneuploidies and copy number variations, a total of 23,116 pregnant women with a singleton pregnancy were recruited for NIPT-Plus. Screening positive results were verified by karyotype analysis and chromosomal microarray analysis after amniocentesis. A total of 264 pregnancies (1.14%) were positive results as predicted by NIPT-Plus, including 233 aneuploidies and 31 copy number variations. Following genetic counseling, 233 (88.26%) pregnant women underwent invasive prenatal diagnosis and 136 were verified as true positives, comprising 72 common trisomies (T21, T18, T13), 47 sex chromosomal abnormalities two rare autosomal aneuploidies (RATs) and 15 copy number variations The positive predictive value for common trisomies, SCAs, RATs and CNVs were 68.57%, 68.12%, 6.67% and 51.72%, respectively. Pregnant women with screen-positive results for common trisomies have higher rates of invasive prenatal diagnosis and pregnancy termination than those with positive results for SCAs, RATs, and CNVs. NIPT-Plus showed a good performance in detecting common trisomies, SCAs and also contributed to detecting pathogenic CNVs, but higher accuracy was required in the detection of RATs. In summary, this study provides a reference for the clinical application of NIPT-Plus for screening fetal chromosomal abnormalities in this region. Therefore, we suggest that NIPT-Plus could be widely used in clinical screening for fetal chromosomal abnormalities in combination with prenatal diagnosis and genetic counseling.

Combined use of karyotyping and copy number variation sequencing technology in prenatal diagnosis

Background

Karyotyping and genome copy number variation sequencing (CNV-seq) are two techniques frequently used in prenatal diagnosis. This study aimed to explore the diagnostic potential of using a combination of these two methods in order to provide a more accurate clinical basis for prenatal diagnosis.

Methods

We selected 822 pregnant women undergoing amniocentesis and separated them into six groups according to different risk indicators. Karyotyping and CNV-seq were performed simultaneously to compare the diagnostic performance of the two methods.

Results

Among the different amniocentesis indicators, abnormal fetal ultrasounds accounted for 39.29% of the total number of examinees and made up the largest group. The abnormal detection rate of non-invasive prenatal testing (NIPT) high risk was 37.93% and significantly higher than the other five groups (P < 0.05). The abnormal detection rate of mixed indicators was significantly higher than the history of the adverse reproductive outcomes group (P = 0.0151). The two methods combined found a total of 119 abnormal cases (14.48%). Karyotyping detected 57 cases (6.93%) of abnormal karyotypes, 30 numerical aberrations, and 27 structural aberrations. CNV-seq identified 99 cases (12.04%) with altered CNVs, 30 cases of chromosome aneuploidies, and 69 structural aberrations (28 pathogenic, eight that were likely pathogenic, and 33 microdeletion/duplication variants of uncertain significance (VUS)). Thirty-seven cases were found abnormal by both methods, 20 cases were detected abnormally by karyotyping (mainly mutual translocation and mostly balanced), and 62 cases of microdeletion/duplication were detected by CNV-seq. Steroid sulfatase gene (STS) deletion was identified at chromosome Xp22.31 in three cases. Postnatal follow-up confirmed that babies manifested skin abnormalities one week after birth. Six fetuses had Xp22.31 duplications ranging from 1.5 Kb to 1.7 Mb that were detected by CNV-seq. Follow-up showed that five babies presented no abnormalities during follow-up, except for one terminated pregnancy due to a history of adverse reproductive outcomes.

Conclusion

The combination of using CNV-seq and karyotyping significantly improved the detection rate of fetal pathogenic chromosomal abnormalities. CNV-seq is an effective complement to karyotyping and improves the accuracy of prenatal diagnosis.

Efficiency of expanded noninvasive prenatal testing in the detection of fetal subchromosomal microdeletion and microduplication in a cohort of 31,256 single pregnancies

Noninvasive prenatal testing (NIPT) is widely used to screen for common fetal chromosomal aneuploidies. However, the ability of NIPT-Plus to detect copy number variation (CNV) is debatable. Accordingly, we assessed the efficiency of NIPT-Plus to detect clinically significant fetal CNV. We performed a prospective analysis of 31,260 singleton pregnancies, included from June 2017 to December 2020. Cell-free fetal DNA was directly sequenced using the semiconductor sequencing platform for women with high-risk CNV with clinically significant results. Fetal karyotyping and chromosomal microarray analysis (or next-generation sequencing) are recommended for invasive diagnostic procedures. Women at low risk with no other abnormal results continued their pregnancies. We analyzed the expanded NIPT results, diagnostic test results, and follow-up information to evaluate its performance in detecting fetal CNV. Of the 31,260 pregnant women who received NIPT-Plus, 31,256 cases were tested successfully, a high risk of clinically significant CNV was detected in 221 cases (0.71%); 18 women refused further diagnosis; 203 women underwent invasive prenatal diagnosis; and 78 true positive cases and 125 false positive cases, with an overall positive predictive value (PPV) of 38.42% and a false positive rate of 0.40%. For known microdeletion/microduplication syndromes (n = 27), the PPVs were 75% DiGeorge syndrome (DGS), 80% 22q11.22 microduplication, 50% Prader-Willi syndrome, and 50% cri-du-chat. For the remaining clinically significant fetal CNVs (n = 175), the combined PPVs were 46.5% (CNVs > 10 Mb) and 28.57% (CNVs ≤ 10 Mb). NIPT-Plus screening for CNV has certain clinical value. NIPT-Plus yielded relatively high PPVs for 22q11.2 microduplication syndrome and DGS, and low to moderate PPVs for other CNVs.

Application of chromosome microarray analysis and karyotyping in diagnostic assessment of abnormal Down syndrome screening results

Background

Down syndrome (DS) is the most common congenital cause of intellectual disability and also leads to numerous metabolic and structural problems. This study aims to explore the application value of chromosomal microarray analysis (CMA) and karyotyping in prenatal diagnosis for pregnant women with abnormal DS screening results.

Methods

The study recruited 1452 pregnant women with abnormal DS screening results including 493 with an enlarged nuchal translucency thickness (NT ≥ 2.5 mm) and 959 with an abnormal second-trimester maternal serum biomarker screening results. They underwent amniocentesis to obtain amniotic fluid for CMA and karyotyping.

Results

CMA identified 74/1452 abnormal results, which was more efficient than karyotyping (51/1452, P < 0.05.) CMA is equivalent to traditional karyotyping for identifying aneuploidies. Compared to karyotyping CMA identified 1.90% more copy number variants (CNVs) ranging from 159Kb to 6496Kb. However, 34.4% of them were recurrent pathogenic CNVs associated with risk of neurodevelopmental disorders. CMA identified 13 variants of uncertain significance (VUS) results and 1 maternal uniparental disomy (UPD) of chromosome 7. Karyotyping identified 3 mosaic sex chromosome aneuploidy and 4 balanced translocation which could not be identified by CMA. In enlarged NT group, karyotyping identified 80.9% abnormal results while in serum screening group karyotyping identified 35.7%. However, the incidence of pathogenic/likely pathogenic (P/LP) CNVs was nearly the same in both groups. That was because aneuploidies and gross duplication/deletion were previously screened out by NT scan.

Conclusions

CMA and karyotyping have both advantages and disadvantages in prenatal diagnosis of pregnant women with abnormal DS screening results. However, there was not enough evidence to support routine CMA in pregnant women with abnormal DS screening results.

Invasive Prenatal Diagnostic Testing for Aneuploidies in Singleton Pregnancies: A Comparative Review of Major Guidelines

Sophisticated screening protocols for genetic abnormalities constitute an important component of current prenatal care, aiming to identify high-risk pregnancies and offer appropriate counseling to parents regarding their options. Definite prenatal diagnosis is only possible by invasive prenatal diagnostic testing (IPDT), mainly including amniocentesis and chorionic villous sampling (CVS). The aim of this comparative review was to summarize and compare the existing recommendations on IPDT from the most influential guidelines. All the reviewed guidelines highlight that IPDT is indicated based on a positive screening test rather than maternal age alone. Other indications arise from medical history and sonography, with significant variations identified between the guidelines. The earlier time for amniocentesis is unequivocally set at ≥15 gestational weeks, whereas for CVS, the earlier limit varies from ≥10 to ≥11 weeks. Certain technical aspects and the overall approach demonstrate significant differences. Periprocedural management regarding Rhesus alloimmunization, virologic status and use of anesthesia or antibiotics are either inconsistent or insufficiently addressed. The synthesis of an evidence-based algorithm for IPDT is of crucial importance to healthcare professionals implicated in prenatal care to avoid unnecessary interventions without compromising optimal prenatal care.

The accuracy and feasibility of noninvasive prenatal testing in a consecutive series of 20,626 pregnancies with different clinical characteristics

Background

To evaluate the accuracy and feasibility of noninvasive prenatal testing (NIPT) according to the results of NIPT and pregnancy outcomes with different indications.

Methods

Between October 2014 and December 2020, 20,626 pregnant women who received NIPT were included in this study. The positive predictive value (PPV) of trisomy 21, 18, and 13 (T21, T18, T13), sex chromosome abnormalities (SCAs), other chromosomal aneuploidies, and chromosomal microdeletion/microduplication were calculated. The positive results of NIPT were confirmed by amniocentesis, Karyotype analysis, and chromosome microarray analysis (CMA).

Results

In total, 263 positive cases (263/20,626, 1.28%) were detected by NIPT, of which T21, T18, and T13 were 69, 26, and 9 cases, respectively. Sex chromosome abnormalities (SCAs), other chromosomal aneuploidies, and copy number variants (CNVs) were 69, 12, and 38 cases, respectively. There were true positive in 49 of T21, 13 of T18, 1 of T13, 32 of SCAs, 1 of other chromosomal aneuploidies, and 15 of CNVs. The NIPT sensitivity of T21, T18, T13, SCAs, other chromosomal aneuploidies, and CNVs was all 100%, the specialty was 99.90%, 99.94%, 99.96%, 99.82%, 99.95%, 99.89%, and the PPV was 71.01%, 50.00%, 11.11%, 46.38%, 8.33%, 39.47%, respectively. The PPV was high in T21, moderate in T18 and SCAs, and low in T13 and other chromosomal abnormalities.

Conclusion

NIPT has high accuracy, specificity and and can effectively avoid the occurrence of birth defects, but it cannot replace prenatal diagnosis. The accuracy, specificity, and sensitivity of NIPT in detecting sex chromosomes, chromosome microdeletion/microduplication, and other chromosomal abnormalities should be improved.

Validity and Utility of Non-Invasive Prenatal Testing for Copy Number Variations and Microdeletions: A Systematic Review

Valid data on prenatal cell-free DNA-based screening tests for copy number variations and microdeletions are still insufficient. We aimed to compare different methodological approaches concerning the achieved diagnostic accuracy measurements and positive predictive values. For this systematic review, we searched the Scopus and PubMed databases and backward citations for studies published between 2013 and 4 February 2022 and included articles reporting the analytical and clinical performance of cfDNA screening tests for CNVs and microdeletions. Of the 1810 articles identified, 32 met the criteria. The reported sensitivity of the applied tests ranged from 20% to 100%, the specificity from 81.62% to 100%, and the PPV from 3% to 100% for cases with diagnostic or clinical follow-up information. No confirmatory analysis was available in the majority of cases with negative screening results, and, therefore, the NPVs could not be determined. NIPT for CNVs and microdeletions should be used with caution and any developments regarding new technologies should undergo strict evaluation before their implementation into clinical practice. Indications for testing should be in correlation with the application guidelines issued by international organizations in the field of prenatal diagnostics.

The Fetal Sequencing Consortium (FSC): The value of multidisciplinary dialogue and collaboration

Prenatal diagnosis of fetal structural anomalies is entering a new phase due to advances in diagnostic sequencing. The creation of an international, multi-disciplinary Fetal Sequencing Consortium (FSC) has provided a forum for regular dialogue and collaboration between diverse clinicians and scientists focused on the interpretation and understanding of sequencing results. The creation of an international fetal sequencing repository utilizing the Global Alliance for Genomics and Health (GA4GH) standards will further expand our ability to clinically interpret the fetal genome, advancing both clinical care and scientific discovery. This article is protected by copyright. All rights reserved.

Fetal reduction and twins

Infertility treatments have allowed millions of couples to have their own children, but resultant multiple pregnancies with their increased morbidity and mortality have been a significant complication. Fetal reduction was developed to ameliorate this issue. Over 30 years of publications show that fetal reduction has been highly successful in substantially reducing both mortality and morbidity related to multiple pregnancies. As with most radically new techniques, initial cases were in the "nothing to lose" category. With experience, indications liberalize, and quality of life issues gain relevance. The overall risks of twin pregnancy are not twice that of singleton pregnancy; they are about 4 to 5 times higher. In experienced hands, the combination of genetic testing by chorionic villus sampling followed by fetal reduction has made the outcomes of most multiple pregnancies statistically equivalent to those of pregnancies with lower fetal numbers. Use of microarray analysis to better determine fetal genetic health before deciding on which fetus(es) to keep or reduce further improves pediatric outcomes. With increasing experience and lower average starting numbers, the proportion of fetal reductions to a singleton has increased considerably. Twins to a singleton fetal reductions now constitute an increasing proportion of cases performed. Data on such cases show improved outcomes, and we believe fetal reduction should be at least discussed and offered to all patients with a dichorionic twin pregnancy or higher. With the increasing reliance on elective single-embryo transfers, monochorionic twins, which have much higher complication rates than dichorionic twins, have increased substantially. Furthermore, monochorionic twins cannot be readily and safely reduced, so the adverse perinatal statistics of elective single-embryo transfer are a major setback for good outcomes. Although elective single-embryo transfer is appropriate for some, we believe that for many couples, the transfer of 2 embryos is generally a more rational approach.

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

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.

Knowledge, attitudes, and practices of healthcare professionals working in prenatal diagnosis toward expanded non-invasive prenatal testing in China

OBJECTIVES

To investigate the knowledge, attitudes, and practices of healthcare professionals (HCPs) working in prenatal diagnosis toward expanded non-invasive prenatal testing (NIPT) in China.

METHODS

We conducted a national online survey among HCPs working in prenatal diagnosis, including specialists in prenatal diagnosis and foetal medicine, obstetricians and gynaecologists, nurses in obstetrics and gynaecology, obstetric ultrasound doctors, and technicians in prenatal diagnosis laboratories. A total of 1882 questionnaires were collected, among which 1822 questionnaires met the research criteria and were included in the analysis.

RESULTS

More than 99% of all participants opted for NIPT for trisomies 21, 18, and 13. The rates of support for expanded NIPT for sex chromosome aneuploidies, rare autosomal trisomies, microdeletions and microduplications, and single-gene disorders were 93.9%, 88.6%, 89.4%, and 86.8%, respectively. Specialists in prenatal diagnosis and foetal medicine had greater knowledge but were less likely to support expanded NIPT compared to other participants. Knowledge increased with educational level, whereas support for expanded NIPT decreased with educational level.

CONCLUSIONS

More than 80% of HCPs working in prenatal diagnosis in China expressed support for expanding NIPT to conditions other than common trisomies. The degree of knowledge was negatively associated with the rate of support.

Fetomaternal microchimerism and genetic diagnosis: On the origins of fetal cells and cell-free fetal DNA in the pregnant woman

During pregnancy several types of fetal cells and fetal stem cells, including pregnancy-associated progenitor cells (PAPCs), traffic into the maternal circulation. Whereas they also migrate to various maternal organs and adopt the phenotype of the target tissues to contribute to regenerative processes, fetal cells also play a role in the pathogenesis of maternal diseases. In addition, cell-free fetal DNA (cffDNA) is detectable in the plasma of pregnant women. Together they constitute the well-known phenomenon of fetomaternal microchimerism, which inspired the concept of non-invasive prenatal testing (NIPT) using maternal blood. An in-depth knowledge concerning the origins of these fetal cells and cffDNA allows a more comprehensive understanding of the biological relevance of fetomaternal microchimerism and has implications for the ongoing expansion of resultant clinical applications.

The potential of expanded noninvasive prenatal screening for detection of microdeletion and microduplication syndromes

OBJECTIVES

To evaluate the clinical potential of a higher resolution noninvasive prenatal screening (NIPS-Plus) test for detection of microdeletion/microduplication syndromes (MMS) in addition to common aneuploidies.

METHODS

In a multicenter prospective study, 37,002 pregnant women with unremarkable first-trimester ultrasound scans had a NIPS-Plus test. Ultrasound screen positive women were not included in this study.

RESULTS

Of 36,970 ultrasound negative women there were 291 NIPS-Plus screen positive results indicating 237 aneuploidies and 54 MMS. Following amniocentesis, 171 (72%) were confirmed as genuine, comprising 3 T13s, 10 T18s, 61 T21s, 70 SCAs and 27 MMS. The PPV for MMS with unremarkable ultrasound findings was 50%. Routine clinical examination of children born from NIPS-Plus negative pregnancies revealed no obvious signs of chromosome disease syndromes at one year of age.

CONCLUSIONS

NIPS-Plus has the potential for clinical utility not only for routine aneuploid screening but also for MMS that do not show overt signs during early pregnancy ultrasound screening. We suggest that ultrasound with NIPS-Plus in combination with appropriate counselling could be considered as a comprehensive first-tier prenatal screening approach for all pregnant women.

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

Background

Our 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).

Methods

A retrospective analysis was performed on pregnant women who had failed NIPS tests.

Results

Among 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.

Conclusion

Prenatal 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.

Understanding False Negative in Prenatal Testing

A false negative can happen in many kinds of medical tests, regardless of whether they are screening or diagnostic in nature. However, it inevitably poses serious concerns especially in a prenatal setting because its sequelae can mark the birth of an affected child beyond expectation. False negatives are not a new thing because of emerging new tests in the field of reproductive, especially prenatal, genetics but has occurred throughout the evolution of prenatal screening and diagnosis programs. In this paper we aim to discuss the basic differences between screening and diagnosis, the trade-offs and the choices, and also shed light on the crucial points clinicians need to know and be aware of so that a quality service can be provided in a coherent and sensible way to patients so that vital issues related to a false negative result can be appropriately comprehended by all parties.

Current controversies in prenatal diagnosis: Expanded NIPT that includes conditions other than trisomies 13, 18, and 21 should be offered

Non-invasive prenatal testing (NIPT) based on analysis of cell free DNA circulating in the maternal plasma has been available clinically to screen for chromosomal abnormalities since 2011. There is significant evidence to suggest that NIPT has revolutionised prenatal screening for the common trisomies 13, 18, and 21. However, the evidence in favour of its extended use to screen for conditions other than these trisomies remains a topic of debate with no national or international organisation supporting clinical implementation for these indications. In the debate presented here - "Expanded NIPT that includes conditions other than trisomies 13, 18, and 21 should be offered" - we will see the pros and cons of screening for a wider range of chromosomal problems. The discussion presented swung the vote from 65% in favour and 35% against before the arguments were voiced to 41% in favour and 59% against. This significant swing in the vote indicates that the majority of our community feel more evidence is required before clinical implementation of extended NIPT.

Prenatal diagnosis of 913 fetuses samples using copy number variation sequencing

Background

The present study aimed to explore the etiological relationship between fetal abnormalities and copy number variations (CNVs) with the aim of intervening and preventing the birth of children with birth defects in time.

Methods

Samples of 913 fetuses with puncture indications were collected from January 2017 to December 2019. Karyotype analysis and CNV sequencing (CNV‐seq) testing was performed for fetuses with ultrasonic abnormalities, a high risk of Down’s syndrome and an adverse birth history. All cases were followed up.

Results

In total, 123 cases (13.47%) had abnormal karyotypes, including 109 cases with chromosome number abnormalities and 14 cases of chromosomal structural abnormalities. Thirty‐seven (4.05%) cases with pathogenic CNVs were detected. The detection rate of pathogenicity CNVs was 12.82% for mixed indications, followed by 7.5% for an adverse birth history, 5.88% at high risk of non‐invasive prenatal testing, 5.00% with an abnormal ultrasonic marker, 1.89% at high risk of screening for Down's syndrome and 1.45% with advanced maternal age. There were 12 (1.31%) cases with microduplications and 25 (2.74%) cases with microdeletions. Trisomy 21 (39.02%), trisomy 18 (13.82%) and Turner syndrome (9.76%) were the top three chromosome abnormalities. There were 104, 746 and 63 cases in the 11–13 weeks, 14–27 weeks 28–38 weeks gestational ages, respectively. The abnormal rates of fetal chromosome aneuploidy and the rate of pathogenic CNVs were decreased and increased with the increase of gestational age (p < 0.05), respectively.

Conclusions

Compared with karyotype analysis, CNV‐seq can improve the detection rate of chromosomal abnormalities. CNV‐seq combined karyotype analysis should be performed simultaneously in fetuses with puncture indications.

Patient attitudes toward prenatal diagnostic testing during antenatal care in an urban population

OBJECTIVE

Investigate factors that influence the decision to accept or decline diagnostic testing for pregnant women referred for genetic counseling.

METHODS

Cross sectional anonymous survey of pregnant women undergoing genetic counseling at a tertiary care referral center. Subjects' perceived risk of procedure related loss and fetal chromosomal problem were obtained via survey where patients rated risk from 0 (no risk) to 10 (highest risk).

RESULTS

There were no differences in sociodemographic factors between women undergoing a diagnostic procedure compared to those not undergoing a procedure. As the perceived risk for having a baby with genetic problem increased by one point, the estimated odds of having the diagnostic procedure increased by 43% controlling for the perceived risk of procedure related loss (p < .0001). Similarly, as the perceived risk of miscarriage increased by one point, the odds of having the diagnostic procedure decreased by 40%, controlling for the perceived risk of having a baby with a genetic problem (p < .0001). The main reason women cited for not undergoing a procedure was fear of procedure related loss.

CONCLUSIONS

Pregnant women that decline diagnostic testing have a higher perceived risk of procedure related loss and lower perceived risk of fetal chromosomal abnormality than those who accept.

Usefulness of copy number variant detection following monogenic disease exclusion in prenatal diagnosis

Aim

Families with an adverse history of monogenic disease focus on single‐gene diagnosis instead of low‐depth whole‐genome sequence, during subsequent pregnancies. The aim of this study was to assess the potential usefulness of low‐depth whole‐genome sequencing (copy number variant sequencing [CNV‐seq]) detection following monogenic disease exclusion in prenatal diagnosis.

Methods

A total of 285 families with a history of monogenic disease (of 41 different types; eliminated during the current pregnancy) were recruited and retrospectively analyzed. Low‐depth whole‐genome sequencing (CNV‐Seq, Next‐Seq CN500 platform) was performed for all fetuses.

Results

The CNV detection results of the 285 samples were as follows: one case of 18‐trisomy chimera (0.35%), one case of pathogenic 3q29 microdeletion syndrome CNV (0.35%), four cases of variant of uncertain significance (VUS) CNVs (1.40%), and four cases of Duchenne muscular dystrophy (DMD) carriers (1.40%); and the remaining samples were normal (96.15%). Of note, 2/285 (0.70%) samples still exhibited pathogenic abnormalities. All positive samples were followed up where the two cases of pathogenic abnormalities elected the pregnancy termination, while the four VUS cases and four DMD‐carrier cases were born healthy.

Conclusion

In cases where prenatal fetal monogenic disease has been ruled out, CNV detection is still beneficial and should be performed to prevent missed pathogenic CNVs. However, the costs need to be balanced against benefits, and the research will need to assess other types of testing.

New cut-off values for screening of trisomy 21, 18 and open neural tube defects (ONTD) during the second trimester in pregnant women with advanced maternal age

Background

To determine whether advanced maternal age (AMA) causes changes in the maternal serum markers of Trisomy 21, 18 and open neural tube defects (ONTD) during the second trimester of pregnancy. Our research aims to develop new cut-off values for AMA in order to reduce the need for further invasive testing.

Methods

This retrospective cohort study involved 12,739 pregnant women with AMA and 197,101 pregnant women with non-AMA. We then compared the two groups with respect to the positive rate and positive predictive value (PPV) of Trisomy 21, 18 and ONTD. Pregnant women with Trisomy 21, 18 and ONTD were diagnosed by karyotyping the amniotic fluid and by ultrasound diagnosis.

Results

Compared to the non-AMA group, the multiple of the median (MOM) of free beta- human chorionic gonadotropin (free β-hCG), alpha-fetoprotein (AFP), and the risk value forTrisomy 21, were significantly higher in the AMA group (all P < 0.001). The positive rates of Trisomy 21, 18, and ONTD in the AMA group were significantly higher than those in the control group (all P < 0.001). In the AMA group, the PPVs for Trisomy 21 and other deformities were significantly higher (all P < 0.001), although the PPVs for Trisomy 18 and ONTD were similar to those of the non-AMA group. The area under the curve (AUC) values for the AMA group were higher than the non-AMA group, based on free β-hCG MoM, AFP MoM, and the risk value of Trisomy 21. The cut-off value for the risk value of Trisomy 21 was 1/172 for the AMA, group and 1/780 for the non-AMA group.

Conclusions

The positive rates for Trisomy 21, 18 and ONTD, and the PPV for Trisomy 21 and other deformities were significantly higher in the AMA group. It is essential for pregnant women with AMA to be tested using appropriate cut-off values of serum markers screening for Trisomy 21 during the second trimester of pregnancy to improve the efficacy of prenatal screening and reduce the need for further invasive testing.

How often do we incidentally find a fetal abnormality at the routine third-trimester growth scan? A population-based study

BACKGROUND

Third-trimester scans are increasingly used to try to prevent adverse outcomes associated with abnormalities of fetal growth. Unexpected fetal malformations detected at third-trimester growth scans are rarely reported.

OBJECTIVE

To determine the incidence and type of fetal malformations detected in women attending a routine third-trimester growth scan.

STUDY DESIGN

This was a population-based study of all women with singleton pregnancy attending antenatal care over a 2-year period in Oxfordshire, UK. Women who had a viable singleton pregnancy at dating scan were included. Women had standard obstetrical care including the offer of a routine dating scan and combined screening for trisomies; a routine anomaly scan at 18 to 22 weeks; and a routine third-trimester growth scan at 36 weeks. The third-trimester scan comprises assessment of fetal presentation, amniotic fluid, biometry, umbilical and middle cerebral artery Dopplers, but no formal anatomic assessment is undertaken. Scans are performed by certified sonographers or clinical fellows (n=54), and any suspected abnormalities are evaluated by a team of fetal medicine specialists. We assessed the frequency and type of incidental congenital malformations identified for the first time at this third-trimester scan. All babies were followed-up after birth for a minimum of 6 months.

RESULTS

There were 15,244 women attending routine antenatal care. Anomalies were detected in 474 (3.1%) fetuses as follows: 103 (21.7%) were detected before the anomaly scan, 174 (36.7%) at the anomaly scan, 11 (2.3%) after the anomaly scan and before the third-trimester scan, 43 (9.1%) at the third-trimester scan and 143 (30.2%) after birth. The 43 abnormalities were found in a total of 13,023 women who had a 36 weeks scan, suggesting that in 1 out of 303 (95% confidence interval, 233-432) women attending such a scan, a new malformation was detected. Anomalies detected at the routine third-trimester scan were of the urinary tract (n=30), central nervous system (5), simple ovarian cysts (4), chromosomal (1), splenic cyst (1), skeletal dysplasia (1), and cutaneous lymphangioma (1). Most urinary tract anomalies were renal pelvic dilatation, which showed spontaneous resolution in 57% of the cases.

CONCLUSION

When undertaking a program of routine third-trimester growth scans in women who have had previous screening scans, an unexpected congenital malformation is detected in approximately 1 in 300 women.

A cross-sectional survey of pregnant women's knowledge of chromosomal aneuploidy and microdeletion and microduplication syndromes

OBJECTIVE

The purpose of this survey is to evaluate the knowledge of Chinese pregnant women about fetal chromosomal aneuploidy and microdeletion and microduplication syndromes, and Non-invasive prenatal testing (NIPT).

STUDY DESIGN

Written questionnaires were distributed to pregnant women who visited the fetal medicine clinic of the third affiliated hospital of Guangzhou medical university. A total of 330 questionnaires were given. Twenty-two questionnaires with incomplete information were excluded from further analysis. The remaining 308 cases were incorporated into the final analysis. Data were analyzed using IBM SPSS Statistics 26. Comparisons between categorical variables were tested by the use of crosstabs and χ 2 test.

RESULTS

Among pregnant women, the recognition of Down syndrome was the highest (93.5 %), followed by maternal serum screening (74.0 %) and NIPT (69.2 %) for chromosomal aneuploidy. The awareness rates of chromosomal microdeletions and microduplications (18.2 %) and monogenic disorders (13.3 %) were the lowest. There were no significant differences in age, education, and conception way between pregnant women (P > 0.05). When asked the opinion on increasing the testing range of NIPT, more than 50 % of pregnant women chose to follow the provider's advice.

CONCLUSION

More than half of pregnant women lacked knowledge of screening methods for fetal chromosomal abnormalities. Less than 20 % of pregnant women knew microdeletion microduplication syndromes. To enhance the understanding of chromosomal abnormalities can ensure that women can actively choose tests rather than passively agreeing to their provider's recommendations so as to avoid missing the optimal prenatal screening time.

Influence of the detection of parent-of-origin on the pregnancy outcomes of fetuses with copy number variation of unknown significance

The widespread application of high-resolution chromosome detection technology in clinical practice has identified many variants of unknown significance (VOUS) in prenatal diagnosis. The purpose of this study was to prospectively analyze the chromosomal results of parents and the follow-up information of pregnancy outcomes of prenatal samples with VOUS, so as to determine the influence of the detection of parent-of-origin on the pregnancy outcomes of fetuses with VOUS. The present study analyzed amniotic fluid samples obtained from women with different risk indications between February 2017 and December 2018. The samples were subjected to copy number variation sequencing, and detection of parent-of-origin was suggested in cases of samples with VOUS. The pregnancy outcome was followed up. In a total of 14073 amniotic fluid samples, 729 cases of VOUS were detected (5.2%, 729/14073) and 721 cases were followed up successfully. Among the 721 cases, 525 patients agreed to detect the parent-of-origin (72.8%, 525/721). It was revealed that the VOUS in 460 of the fetuses were hereditary (87.6%, 460/525). The percentages of abnormal pregnancy outcomes (included pregnancy loss, fetal pathological abnormality, preterm delivery, neonatal death, birth defects) in the inherited, de novo, and refusal to detect the parent-of-origin (i.e. unknown origin) groups were 4.3% (20/460), 6.2% (4/65), and 6.6% (13/196), respectively. There was no significant difference among the three groups (P > 0.05). The rate of voluntary termination of pregnancy (TOP) in the unknown origin group was significantly higher than that in the group that had determined the parent-of-origin (14.3% vs 7.4%, P = 0.005). There is currently no evidence that suggests that the proportion of abnormal pregnancy outcomes is higher in fetuses with VOUS than in other fetuses. However, the present study revealed that determining the parent-of-origin affects the decision to undergo voluntary TOP, as the rate of voluntary TOP in the group that refused detection was higher than that in the group that consented.

Understanding attitudes and behaviors towards cell-free DNA-based noninvasive prenatal testing (NIPT): A survey of European health-care providers

Cell-free DNA-based noninvasive prenatal testing (cfDNA) is a relatively new screening tool that analyzes cfDNA circulating in maternal plasma to screen for aneuploidies. Since its introduction, cfDNA has been rapidly adopted by health care providers (HCPs). This rapid adoption, as well as progressive developments in the technology, requires professional societies to continuously update their guidelines to indicate the broadening scope both in terms of test indications and patient populations for whom it has become the appropriate primary test. CfDNA testing, initially applied to high-risk patients, is now largely considered an option for all patients. For HCPs, the rapid introduction of cfDNA into clinical practice has come with the requirement to stay up-to-date and accurately informed. We performed a survey to understand the current practices and views of European HCPs on the use of cfDNA. European HCPs were surveyed on several topics such as familiarity with cfDNA-based noninvasive prenatal testing (NIPT), current usage, patient counseling, test menu expansion, and future perspectives. The results of this survey demonstrate increasing usage and awareness of cfDNA-based NIPT in five European countries (UK, France, Germany, Spain and Italy). Major barriers to implementation include cost and a lack of physician education on NIPT.

Noninvasive prenatal testing for chromosome aneuploidies and subchromosomal microdeletions/microduplications in a cohort of 42,910 single pregnancies with different clinical features

Background

Since the discovery of cell-free DNA (cfDNA) in maternal plasma, it has opened up new approaches for non-invasive prenatal testing. With the development of whole-genome sequencing, small subchromosomal deletions and duplications could be found by NIPT. This study is to review the efficacy of NIPT as a screening test for aneuploidies and CNVs in 42,910 single pregnancies.

Methods

A total of 42,910 single pregnancies with different clinical features were recruited. The cell-free fetal DNA was directly sequenced. Each of the chromosome aneuploidies and the subchromosomal microdeletions/microduplications of PPV were analyzed.

Results

A total of 534 pregnancies (1.24%) were abnormal results detected by NIPT, and 403 pregnancies had underwent prenatal diagnosis. The positive predictive value (PPV) for trisomy 21(T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosome aneuploidies (SCAs), and other chromosome aneuploidy was 79.23%, 54.84%, 13.79%, 33.04%, and 9.38% respectively. The PPV for CNVs was 28.99%. The PPV for CNVs ≤ 5 Mb is 20.83%, for within 5–10 Mb 50.00%, for > 10 Mb 27.27% respectively. PPVs of NIPT according to pregnancies characteristics are also different.

Conclusion

Our data have potential significance in demonstrating the usefulness of NIPT profiling not only for common whole chromosome aneuploidies but also for CNVs. However, this newest method is still in its infancy for CNVs. There is still a need for clinical validation studies with accurate detection rates and false positive rates in clinical practice.

The current and future impact of genome-wide sequencing on fetal precision medicine

Next-generation sequencing and other genomic technologies are transforming prenatal and reproductive screening and testing for fetal genetic disorders at an unprecedented pace. Original approaches of screening and testing for fetal genetic and genomic disorders were focused on a few more prevalent conditions that were easily diagnosable with pre-genomic era diagnostic tools. First, chromosomal microarray analysis and then next-generation sequencing brought technology capable of more detailed genomic evaluation to prenatal genetic screening and diagnosis. This has facilitated parallel introduction of a variety of new tests on maternal blood samples, including expanded carrier screening and cell-free DNA-based non-invasive screening for fetal aneuploidy, selected copy number variants, and single-gene disorders. Genomic tests on fetal DNA samples, obtained primarily through amniocentesis or chorionic villus sampling, include chromosomal microarray analysis and gene panel and exome sequencing. All these form the diagnostic pillar of the emerging field of fetal precision medicine, but their implementation is associated with ethical, counseling and healthcare resource utilization challenges. We discuss where in the reproductive and prenatal care continuum these exciting new technologies are integrated, along with associated challenges. We propose areas of priority for research to gain the data in support of their responsible implementation into clinical reproductive and prenatal care.

Characteristics and mode of inheritance of pathogenic copy number variants in prenatal diagnosis

BACKGROUND

Microdeletions and microduplications can occur in any pregnancy independent of maternal age. The spectrum and features of pathogenic copy number variants including the size, genomic distribution, and mode of inheritance are not well studied. These characteristics have important clinical implications regarding expanding noninvasive prenatal screening for microdeletions and microduplications.

OBJECTIVES

The aim was to investigate the spectrum and characteristics of pathogenic copy number variants in prenatal genetic diagnosis and to provide recommendations for expanding the scope of noninvasive prenatal screening for microdeletions and microduplications.

STUDY DESIGN

This was a retrospective study of 1510 pregnant women who underwent invasive prenatal diagnostic testing by chromosomal microarray analysis. Prenatal samples were retrieved by amniocentesis or chorionic villus sampling and sent to our prenatal genetic diagnosis laboratory for chromosomal microarray analysis. The risk of carrying a fetus with pathogenic copy number variants is stratified by the patients' primary indication for invasive testing. We searched the literature for published prenatal chromosomal microarray data to generate a large cohort of 23,865 fetuses. The characteristics and spectrum of pathogenic copy number variants including the type of aberrations (gains or losses), genomic loci, sizes, and the mode of inheritance were studied.

RESULTS

Overall, 375 of 23,865 fetuses (1.6%) carried pathogenic copy number variants for any indication for invasive testing, and 44 of them (11.7%) involve 2 or more pathogenic copy number variants. A total of 428 pathogenic copy number variants were detected in these fetuses, of which 280 were deletions and 148 were duplications. Three hundred sixty (84.1%) were less than 5 Mb in size and 68 (15.9%) were between 5 and 10 Mb. The incidence of carrying a pathogenic copy number variant in the high-risk group is 1 in 36 and the low-risk group is 1 in 125. Parental inheritance study results were available for 311 pathogenic copy number variants, 71 (22.8%) were maternally inherited, 36 (11.6%) were paternally inherited, and 204 (65.6%) occurred de novo.

CONCLUSION

Collectively, pathogenic copy number variants are common in pregnancies. High-risk pregnancies should be offered invasive testing with chromosomal microarray analysis for the most comprehensive investigation. Detection limits on size, parental inheritance, and genomic distribution should be carefully considered before implementing copy number variant screening in expanded noninvasive prenatal screening.

The contingent use of cell-free fetal DNA for prenatal screening of trisomies 21, 18, 13 in pregnant women within a national health service: A budget impact analysis

OBJECTIVE

Non-invasive prenatal testing (NIPT) based on cell-free fetal DNA (cffDNA) is highly accurate in the detection of common fetal autosomal trisomies. Aim of this project was to investigate short-term costs and clinical outcomes of the contingent use of cffDNA for prenatal screening of trisomies 21, 18, 13 within a national health service (NHS).

METHODS

An economic analysis was developed from the perspective of the Italian NHS to compare two possible scenarios for managing pregnant women: women managed according to the Standard of Care screening (SoC) vs a cffDNA scenario, where Harmony Prenatal Test was introduced as a second line screening choice for women with an "at risk" result from SoC screening.

RESULTS

The introduction of cffDNA as a second line screening test, conditional to a risk ≥ 1:1,000 from SoC screening, showed a 3% increase in the detection of trisomies, with a 71% decrease in the number of invasive tests performed. Total short-term costs (pregnancy management until childbirth) decreased by € 19 million (from € 84.5 to 65.5 million).

CONCLUSION

The adoption of the Harmony Prenatal Test in women resulting at risk from SoC screening, implied a greater number of trisomies detection, together with a reduction of the healthcare costs.

The epidemic of abnormal copy number variant cases missed because of reliance upon noninvasive prenatal screening

OBJECTIVE

To assess the implications of increasing utilization of noninvasive prenatal screening (NIPS), which may reach 50% with the concomitant decrease in diagnostic procedures (DPs) for its impact on detection of chromosomal abnormalities.

METHODS

We studied our program's statistics over 5 years for DPs and utilization of array comparative genomic hybridization (aCGH). We then modeled the implications in our program if DP had not fallen and nationally of a 50% DP and aCGH testing rate using well-vetted expectations for the diagnosis of abnormal copy number variants (CNVs).

RESULTS

Our DP fell 40% from 2013-2017. Utilization of aCGH for DP nearly tripled. We detected 28 abnormal CNVs. If DP had not fallen, we likely would have detected 60. With 4 million US births per year, 2 million DPs would detect 30 000 abnormal CNVs and 4000 standard aneuploidies. At a 1/500 complication-pregnancy loss rate, the detection/complication ratio is 8.5/1.

CONCLUSIONS

Noninvasive prenatal screening has significantly changed the practice of prenatal screening. However, while increasing the detection of Down syndrome, the concomitant decrease in DP and lack of aCGH results in missing many more abnormalities than the increase in Down syndrome and complications of DP combined. From a public health perspective, such represents a missed opportunity for overall health care delivery.

Impact of introduction of noninvasive prenatal testing on uptake of genetic testing in fetuses with central nervous system anomalies

OBJECTIVE

To evaluate the impact of introduction of noninvasive prenatal testing (NIPT) on the uptake of invasive testing in pregnancies complicated by fetal central nervous system (CNS) anomalies.

METHODS

Retrospective review of all singleton pregnancies complicated by fetal CNS anomalies seen at a single tertiary center between 2010 and 2017. Cases who had undergone invasive testing or NIPT prior to the diagnosis of the CNS anomaly were excluded. Cases were segregated according to whether they were seen prior to introduction of NIPT (group A, 2010-2013) or thereafter (group B, 2014-2017). We examined the rate of invasive and noninvasive genetic testing in each group.

RESULTS

We retrieved 500 cases: 308 (62%) were isolated CNS anomalies, and 192 (38%) had additional structural anomalies. In the total cohort, 165 women (33%) underwent expectant management with no further prenatal genetic testing, 166 (33%) had invasive testing, 52 (10%) had NIPT, and 117 pregnancies (23%) were terminated without further prenatal investigations. The introduction of NIPT significantly decreased the number of pregnancies having no testing (44% group A vs 22% in group B, p < .0001), particularly in the group presenting with isolated ventriculomegaly, but did not affect the uptake of invasive testing (34% vs 32%, respectively; p = .61). NIPT would have missed 4% of pathogenic copy number variants (CNVs) in the group of cases with isolated brain anomalies and 11% of CNVs in cases with complex anomalies.

CONCLUSIONS

Uptake of invasive prenatal testing in fetuses with brain anomalies was not affected by NIPT. However, the incidence of no genetic testing was significantly reduced. NIPT was a suboptimal testing strategy in this population as it missed a significant number of subchromosomal genetic anomalies.

Population-based trends in invasive prenatal diagnosis for ultrasound-based indications: two decades of change from 1994 to 2016

OBJECTIVE

To assess trends in ultrasound-indicated prenatal diagnostic testing performed over the past two decades in the Australian state of Victoria, in the context of rapidly changing practices in aneuploidy screening and chromosome analysis.

METHODS

This was a retrospective analysis of all ultrasound-indicated prenatal diagnostic testing (amniocentesis and chorionic villus sampling) performed in the state of Victoria between 1994 and 2016. Ultrasound indications for testing included: fetal structural abnormality, fetal death, fetal growth restriction, abnormal amniotic fluid volume, genetic 'soft marker' and unspecified ultrasound abnormality. Maternal age, indication for testing, type of diagnostic procedure, gestational age, type of chromosome analysis (G-banded karyotyping or chromosomal microarray (CMA)) and test results were obtained. Diagnostic yield (i.e. percentage of tests yielding a major abnormality) was analyzed by year, maternal age and gestational age. Statistical analysis was performed using the χ² tests for trend or difference in proportions, as appropriate.

RESULTS

During the 23-year study period, 1 533 317 births were recorded and 16 152 diagnostic procedures were performed for the primary indication of ultrasound abnormality. In recent years, ultrasound abnormality became the most common indication for prenatal invasive testing (29.4% of diagnostic tests between 2013 and 2016) due to a steep decline in testing for other indications such as positive result on combined first-trimester screening or advanced maternal age alone. In 2016, over 95% of ultrasound-indicated procedures were performed with CMA; among these, pathogenic copy number variant (CNV) was the most common (3.5%) abnormality detected, followed by trisomy 21 (2.8%). The diagnostic yield of ultrasound-indicated tests performed < 16 weeks was significantly higher than that of tests performed after 20 weeks (31.5% vs 9.0%).

CONCLUSIONS

Ultrasound-indicated invasive testing is contributing to prenatal diagnosis in new ways in the genomic era. A pathogenic CNV is now the most likely diagnosis after ultrasound-indicated testing, rather than trisomy 21 or other whole-chromosome aneuploidy. Despite steady improvements in first-trimester screening for aneuploidy, the diagnostic yield of ultrasound-indicated tests > 20 weeks has remained stable due to increased utilization of CMA. Procedures performed for structural abnormalities < 16 weeks continue to have the highest diagnostic yield, supporting the benefits of early fetal structural assessment at 11-13 weeks. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Clinical utility of noninvasive prenatal screening for expanded chromosome disease syndromes

PURPOSE

To assess the clinical performance of an expanded noninvasive prenatal screening (NIPS) test ("NIPS-Plus") for detection of both aneuploidy and genome-wide microdeletion/microduplication syndromes (MMS).

METHODS

A total of 94,085 women with a singleton pregnancy were prospectively enrolled in the study. The cell-free plasma DNA was directly sequenced without intermediate amplification and fetal abnormalities identified using an improved copy-number variation (CNV) calling algorithm.

RESULTS

A total of 1128 pregnancies (1.2%) were scored positive for clinically significant fetal chromosome abnormalities. This comprised 965 aneuploidies (1.026%) and 163 (0.174%) MMS. From follow-up tests, the positive predictive values (PPVs) for T21, T18, T13, rare trisomies, and sex chromosome aneuploidies were calculated as 95%, 82%, 46%, 29%, and 47%, respectively. For known MMS (n = 32), PPVs were 93% (DiGeorge), 68% (22q11.22 microduplication), 75% (Prader-Willi/Angleman), and 50% (Cri du Chat). For the remaining genome-wide MMS (n = 88), combined PPVs were 32% (CNVs ≥10 Mb) and 19% (CNVs <10 Mb).

CONCLUSION

NIPS-Plus yielded high PPVs for common aneuploidies and DiGeorge syndrome, and moderate PPVs for other MMS. Our results present compelling evidence that NIPS-Plus can be used as a first-tier pregnancy screening method to improve detection rates of clinically significant fetal chromosome abnormalities.

Factors associated with common and atypical chromosome abnormalities after positive combined first-trimester screening in Chinese women: a retrospective cohort study

BACKGROUND

When cell-free DNA (cfDNA) testing is used as a secondary screening tool following combined first-trimester screening (cFTS), cFTS is used to estimate the prior risk for chromosome abnormalities. This study aimed to assess the factors that are associated with common and atypical abnormalities following cFTS, including cFTS risk, advanced maternal age, increased nuchal translucency (NT) ≥3.5 mm, and abnormal levels of serum markers.

METHODS

We reviewed a historical cohort of 1855 Chinese women carrying singleton pregnancies with a positive cFTS [at a threshold of 1:250 for trisomy (T) 21 or 1:180 for T18] in one public hospital over a five-year period. All chromosome abnormalities were confirmed by invasive prenatal diagnosis (IPD) with karyotyping, with or without array comparative genomic hybridization. Using multivariable binary logistic regression analysis, we determined the parameters that were associated with common and atypical abnormalities.

RESULTS

Overall, the prevalence of common and atypical abnormalities was 6.2 and 1.2%, respectively, and the prevalence increased with the risk of T21 by cFTS. In pregnancies with a risk of T21 > 1 in 100, a high risk of both T21 and T18, an increased NT, or a pregnancy-associated plasma A (PAPP-A) level <  0.2 multiple of medians (MoM), the prevalence of common abnormalities was 12.2, 64.7, 25.5 and 33.8%, respectively, while that of atypical abnormalities was 1.6, 3.9, 4.2, and 7.4%, respectively. In the multivariable binary logistic regression analysis, out of these four factors, only two (increased NT and PAPP_A <  0.2 MoM) were significant predictors of common and atypical abnormalities, respectively. Of all positive cFTS pregnancies, 50.4% did not have any of these four factors, and the prevalence of common and atypical abnormalities was 1.1 and 0.6%, respectively. There were three atypical abnormalities, all of which were mosaicism, and they were detected among women with IPD alone. The ages of these women were ≥ 35 years. All three pregnancies were continued after proper counseling. After giving birth, only one child had mild abnormalities, while the other two were phenotypically normal.

CONCLUSIONS

Our study identified factors associated with common and atypical abnormalities after cFTS. These factors can be used to estimate the prior risk for these abnormalities to help with post-cFTS counseling in terms of choosing between cfDNA testing and IPD.