Noninvasive prenatal testing: need for informed enthusiasm

A Decade of Non-Invasive Prenatal Testing (NIPT) for Chromosomal Abnormalities in Croatia: First National Monocentric Study to Inform Country's Future Prenatal Care Strategy

BACKGROUND

Chromosomal numerical and structural alterations are significant causes of various developmental disorders in foetuses. Non-invasive prenatal testing (NIPT) has emerged as an effective screening tool for detecting common aneuploidies, aiding in the identification of individuals who may require further diagnostic work-up.

METHODS

This retrospective, monocentric observational study evaluates the usage patterns, test choices, turnaround times (TAT), and outcomes of NIPT between 2013 and 2023 on a sample of 2431 pregnant women at a special hospital offering outpatient services and comprehensive gynaecological/obstetric inpatient care. We analysed the trends in NIPT usage, high-risk results, prior screening procedures, as well as factors such as age, gestational age and in vitro fertilisation (IVF) status. NIPT was performed using cell-free foetal DNA (cffDNA) extracted from maternal plasma, followed by library construction, sequencing and result analysis. The sequencing results were aligned with reference genomes, and z-scores were calculated to assess the likelihood of aneuploidy. Statistical significance was set at p < 0.05.

RESULTS

The average age of women undergoing NIPT decreased from 36.1 years in 2013 to 33.01 years in 2023 (p = 0.0287), and mean TAT dropped from 12.44 days in 2013 to 7.08 days in 2023 (p = 0.0121), with the most substantial reduction occurring between 2013 and 2019. The study identified a stable rate of women who underwent IVF seeking prenatal testing, with no statistically significant difference between the first half and the second half of the analysed period (p = 0.2659). Among high-risk results, there were 39 chromosomal abnormalities detected, most of them belonging to trisomy 21 (59%).

CONCLUSIONS

Our findings demonstrate the increasing efficiency and accessibility of NIPT in prenatal care in Croatia, while the significant reduction in TAT and the decreasing age of women undergoing NIPT reflect enhanced operational practices and broader acceptance. Introducing NIPT into the public healthcare system in the Republic of Croatia could improve equitable access to advanced prenatal care and enhance pregnancy outcomes. Future advancements in technology and genetic counselling will further enhance its role, requiring careful attention to ethical and regulatory considerations.

Increased nuchal translucency can be ascertained using transverse planes

BACKGROUND

The detection of increased nuchal translucency is crucial for the assessment risk of aneuploidies and other fetal anomalies.

OBJECTIVE

This study aimed to investigate the ability of a transverse view of the fetal head to detect increased fetal nuchal translucency at 11 to 13 weeks of gestation.

STUDY DESIGN

This was a prospective study enrolling a nonconsecutive series of women who attended our outpatient clinic from January 2020 to April 2021 for combined screening and were examined by operators certified by the Fetal Medicine Foundation. In each patient, nuchal translucency measurements were obtained both from a median sagittal view and from a transverse view. A second sonologist blinded to the results of the first examination obtained another measurement to assess intermethod and interobsever reproducibility.

RESULTS

A total of 1023 women were enrolled. An excellent correlation was found between sagittal and transverse nuchal translucency measurements, with a mean difference of 0.01 mm (95% confidence interval, -0.01 to 0.02). No systematic difference was found between the 2 techniques. The inter-rater reliability (intraclass correlation coefficient, 0.957; 95% confidence interval, 0.892-0.983) and intrarater reliability (intraclass correlation coefficient, 0.976; 95% confidence interval, 0.941-0.990) of axial measurements were almost perfect. Transverse measurements of 3.0 mm identified all cases with sagittal measurements of ≥3.0 with a specificity of 99.7%; transverse measurements of >3.2 mm identified all cases with sagittal measurements of 3.5 mm with a specificity of 99.7%. The time required to obtain transverse nuchal translucency measurements was considerably shorter than for sagittal measurements, particularly when the fetus had an unfavorable position.

CONCLUSION

When the sonogram is performed by an expert sonologist, the difference in nuchal translucency measurement obtained with a transverse or sagittal plane is minimal. Increased nuchal translucency can be reliably identified by using transverse views, and in some cases, this may technically be advantageous.

Noninvasive prenatal testing: from aneuploidy to single genes

Noninvasive prenatal testing has undergone rapid advances in the last few years. Although researchers have long known about circulating pregnancy-based cell-free fragments of DNA in maternal plasma, it was the introduction of massively parallel sequencing that allowed noninvasive prenatal testing to become a widely used clinical test. This review will begin with an in-depth analysis of the use of noninvasive prenatal testing for aneuploidy, including common causes for inaccurate and/or discordant results. It will also review the ongoing expansion of noninvasive prenatal testing to include copy number variants and select single-gene disorders. Finally, integrated throughout the review is a comparison of noninvasive prenatal testing to more traditional screening methods along with some medical and ethical implications of the widespread use of this new technology.

The maternal plasma proteome changes as a function of gestational age in normal pregnancy: a longitudinal study

OBJECTIVE

Pregnancy is accompanied by dramatic physiological changes in maternal plasma proteins. Characterization of the maternal plasma proteome in normal pregnancy is an essential step for understanding changes to predict pregnancy outcome. The objective of this study was to describe maternal plasma proteins that change in abundance with advancing gestational age and determine biological processes that are perturbed in normal pregnancy.

STUDY DESIGN

A longitudinal study included 43 normal pregnancies that had a term delivery of an infant who was appropriate for gestational age without maternal or neonatal complications. For each pregnancy, 3 to 6 maternal plasma samples (median, 5) were profiled to measure the abundance of 1125 proteins using multiplex assays. Linear mixed-effects models with polynomial splines were used to model protein abundance as a function of gestational age, and the significance of the association was inferred via likelihood ratio tests. Proteins considered to be significantly changed were defined as having the following: (1) >1.5-fold change between 8 and 40 weeks of gestation; and (2) a false discovery rate-adjusted value of P < .1. Gene ontology enrichment analysis was used to identify biological processes overrepresented among the proteins that changed with advancing gestation.

RESULTS

The following results were found: (1) Ten percent (112 of 1125) of the profiled proteins changed in abundance as a function of gestational age; (2) of the 1125 proteins analyzed, glypican-3, sialic acid-binding immunoglobulin-type lectin-6, placental growth factor, C-C motif-28, carbonic anhydrase 6, prolactin, interleukin-1 receptor 4, dual-specificity mitogen-activated protein kinase 4, and pregnancy-associated plasma protein-A had more than a 5-fold change in abundance across gestation (these 9 proteins are known to be involved in a wide range of both physiological and pathological processes, such as growth regulation, embryogenesis, angiogenesis immunoregulation, inflammation etc); and (3) biological processes associated with protein changes in normal pregnancy included defense response, defense response to bacteria, proteolysis, and leukocyte migration (false discovery rate, 10%).

CONCLUSION

The plasma proteome of normal pregnancy demonstrates dramatic changes in both the magnitude of changes and the fraction of the proteins involved. Such information is important to understand the physiology of pregnancy and the development of biomarkers to differentiate normal vs abnormal pregnancy and determine the response to interventions.

Cell-free DNA screening in clinical practice: abnormal autosomal aneuploidy and microdeletion results

BACKGROUND

Since its commercial release in 2011 cell-free DNA screening has been rapidly adopted as a routine prenatal genetic test. However, little is known about its performance in actual clinical practice.

OBJECTIVE

We sought to investigate factors associated with the accuracy of abnormal autosomal cell-free DNA results.

STUDY DESIGN

We conducted a retrospective cohort study of 121 patients with abnormal cell-free DNA results from a referral maternal-fetal medicine practice from March 2013 through July 2015. Patients were included if cell-free DNA results for trisomy 21, trisomy 18, trisomy 13, or microdeletions (if reported by the laboratory) were positive or nonreportable. The primary outcome was confirmed aneuploidy or microarray abnormality on either prenatal or postnatal karyotype or microarray. Secondary outcomes were identifiable associations with in vitro fertilization, twins, ultrasound findings, testing platform, and testing laboratory. Kruskal-Wallis or Fisher exact tests were used as appropriate.

RESULTS

A total of 121 patients had abnormal cell-free DNA results for trisomy 21, trisomy 18, trisomy 13, and/or microdeletions. In all, 105 patients had abnormal cell-free DNA results for trisomy 21, trisomy 18, and trisomy 13. Of these, 92 (87.6%) were positive and 13 (12.4%) were nonreportable. The results of the 92 positive cell-free DNA were for trisomy 21 (48, 52.2%), trisomy 18 (22, 23.9%), trisomy 13 (17, 18.5%), triploidy (2, 2.2%), and positive for >1 parameter (3, 3.3%). Overall, the positive predictive value of cell-free DNA was 73.5% (61/83; 95% confidence interval, 63-82%) for all trisomies (by chromosome: trisomy 21, 83.0% [39/47; 95% confidence interval, 69-92%], trisomy 18, 65.0% [13/20; 95% confidence interval, 41-84%], and trisomy 13, 43.8% [7/16; 95% confidence interval, 21-70%]). Abnormal cell-free DNA results were associated with positive serum screening (by group: trisomy 21 [17/48, 70.8%]; trisomy 18 [7/22, 77.8%]; trisomy 13 [3/17, 37.5%]; nonreportable [2/13, 16.7%]; P = .004), and abnormal first-trimester ultrasound (trisomy 21 [25/45, 55.6%]; trisomy 18 [13/20, 65%]; trisomy 13 [6/14, 42.9%]; nonreportable [1/13, 7.7%]; P = .003). There was no association between false-positive rates and testing platform, but there was a difference between the 4 laboratories (P = .018). In all, 26 patients had positive (n = 9) or nonreportable (n = 17) microdeletion results. Seven of 9 screens positive for microdeletions underwent confirmatory testing; all were false positives.

CONCLUSION

The positive predictive value of 73.5% for cell-free DNA screening for autosomal aneuploidy is lower than reported. The positive predictive value for microdeletion testing was 0%. Diagnostic testing is needed to confirm abnormal cell-free DNA results for aneuploidy and microdeletions.

Pre- and post-test genetic counseling for chromosomal and Mendelian disorders

Genetic carrier screening, prenatal screening for aneuploidy, and prenatal diagnostic testing have expanded dramatically over the past 2 decades. Driven in part by powerful market forces, new complex testing modalities have become available after limited clinical research. The responsibility for offering these tests lies primarily on the obstetrical care provider and has become more burdensome as the number of testing options expands. Genetic testing in pregnancy is optional, and decisions about undergoing tests, as well as follow-up testing, should be informed and based on individual patients' values and needs. Careful pre- and post-test counseling is central to supporting informed decision-making. This article explores three areas of technical expansion in genetic testing: expanded carrier screening, non-invasive prenatal screening for fetal aneuploidies using cell-free DNA, and diagnostic testing using fetal chromosomal microarray testing, and provides insights aimed at enabling the obstetrical practitioner to better support patients considering these tests.

Non-invasive prenatal screening for trisomy 21: Consumers' perspectives

Non-invasive prenatal screening (NIPS) has the potential to dramatically increase the prenatal detection rate of Down syndrome because of improvements in safety and accuracy over existing tests. There is concern that NIPS could lead to more negative attitudes towards Down syndrome and less support for individuals with Down syndrome. To assess the impact of NIPS on support for prenatal testing, decision-making about testing, and beliefs or attitudes about Down syndrome, we performed an Internet-based experiment using adults (N = 1,789) recruited through Amazon Mechanical Turk. Participants were randomly assigned to read a mock news article about NIPS, a mock news article about amniocentesis, or no article. The content in the two articles varied only in their descriptions of the test characteristics. Participants then answered questions about their support for testing, hypothetical testing decision, and beliefs and attitudes about Down syndrome. Reading the mock NIPS news article predicted increased hypothetical test uptake. In addition, the NIPS article group also agreed more strongly that pregnant women, in general, should utilize prenatal testing. We also found that the more strongly participants supported prenatal testing for pregnant women, the less favorable their attitudes towards individuals with Down syndrome; providing some evidence that NIPS may indirectly result in more negative perceptions of individuals with this diagnosis.

Comparing genetic counselor's and patient's perceptions of needs in prenatal chromosomal microarray testing

OBJECTIVE

Chromosome microarray analysis is poised to take a significant place in the prenatal setting given its increased yield over standard karyotyping, but concerns regarding ethical and counseling challenges remain, especially associated with the risk of uncertain and incidental findings. Guidelines recommend patients receiving prenatal screening to undergo genetic counseling prior to testing, but little is known about women's specific pre-testing and post-testing informational needs, as well as their preference for return of various types of results.

METHODS

The present study surveys 199 prenatal genetic counselors who have counseled patients undergoing chromosome microarray analysis testing and 152 women who have undergone testing on the importance of understanding pre-test information, return of various types of results, and resources made available following an abnormal finding.

RESULTS

Counselors and patients agree on many aspects, although findings indicate patients consider all available information very important, while genetic counselors give more varying ratings.

CONCLUSION

Counseling sessions would benefit from information personalized to a patient's particular needs and a shared decision-making model, to reduce informational overload and avoid unnecessary anxiety. Additionally, policies regarding the return of various types of results are needed. © 2015 John Wiley & Sons, Ltd.

#36: Prenatal aneuploidy screening using cell-free DNA

Recent advances in technology have created exciting opportunities to expand and improve genetic testing options that are available to women during pregnancy. However, the novelty and complexity of these technologies, combined with the commercial interest to implement these tests rapidly into routine clinical care, have created challenges for physicians and patients and potentially will lead to misunderstanding, misuse, and unintended consequences. The purpose of this document was to aid clinicians in their day-to-day practice of counseling patients regarding prenatal aneuploidy testing options with cell-free DNA screening, which includes how it compares to current testing methods, potential benefits and harms, and its limitations and caveats.