Difference in Procedure-Related Risk of Miscarriage between Early and Mid-Trimester Amniocentesis: A Retrospective Cohort Study

Chapter 2: Non-invasive prenatal diagnosis

Non-invasive prenatal diagnosis of monogenic disorders is becoming integrated into routine clinical care for many indications. This is carried out by testing cell-free DNA extracted from the plasma portion of a maternal blood sample. The cell-free DNA is low in concentration, and consists of a mixture of maternal and fetally-derived DNA which are not easy to separate. Methods used therefore need to be rapid, sensitive and specific, including real-time PCR, digital PCR and next generation sequencing with complex algorithms. Testing may be required for pregnancies with an increased chance of a monogenic disorder due to family history or carrier status, or where there are specific abnormalities identified by ultrasound scan. In these situations, testing is considered to be diagnostic and therefore does not require confirmation by invasive testing. With increased access to genomic technologies, and more diagnoses for rare disease patients, future demand for NIPD and possibilities during pregnancy will continue.

Prenatal Diagnosis of Cleft Lip and Palate: A Retrospective Study

Cleft lip and/or palate are prevalent congenital anomalies. Early and accurate diagnosis allows proper case management. The Objective: This retrospective cohort study aimed to investigate the association between cleft lip and palate and other congenital anomalies. Methods: This study analyzed 17 pregnancies prenatally diagnosed with cleft lip and palate. The investigations consisted of ultrasound examination, fetal karyotyping through amniocentesis, and family tree analysis. In the presence of an abnormal fetal karyotype, the parental karyotype was also indicated. Results: Of the 17 cases identified, 9 (52.94%) were syndromic and 8 (47.06%) were non-syndromic. The genetic syndromes identified in association with cleft lip and palate in this study included translocation syndrome (one case), Patau syndrome, trisomy 13 (seven cases), and Edwards syndrome, mosaic trisomy 18 (one case). Conclusions: A comprehensive approach ensures a thorough assessment and accurate diagnosis. Early detection and a multidisciplinary approach allow appropriate case management.

Noninvasive prenatal testing for the detection of fetal chromosome 17 microduplication: clinical implications and findings

BACKGROUND

 Noninvasive prenatal testing (NIPT) is widely used to screen for fetal aneuploidies. However, there are few reports of using NIPT for screening chromosomal microduplications and microdeletions. This study aimed to investigate the application efficiency of NIPT for detecting chromosomal microduplications.

METHODS

Four cases of copy number gains on the long arm of chromosome 17 (17q12) were detected using NIPT and further confirmed using copy number variation (CNV) analysis based on chromosome microarray analysis (CMA).

RESULTS

The prenatal diagnosis CMA results of the three cases showed that the microduplications in 17q12 (ranging from 1.5 to 1.9 Mb) were consistent with the NIPT results. The karyotypic analysis excluded other possible unbalanced rearrangements. The positive predictive value of NIPT for detecting chromosomal 17q12 microduplication was 75.0%.

CONCLUSIONS

 NIPT has a good screening effect on 17q12 syndrome through prenatal diagnosis, therefore it could be considered for screening fetal CNV during the second trimester. With the clinical application of NIPT, invasive prenatal diagnoses could be effectively reduced while also improving the detection rate of fetal CNV.

"Overestimated technology - underestimated consequences" - reflections on risks, ethical conflicts, and social disparities in the handling of non-invasive prenatal tests (NIPTs)

New technologies create new complexities. Since non-invasive prenatal tests (NIPTs) were first introduced, keeping pace with complexity constitutes an ongoing task for medical societies, politics, and practice. NIPTs analyse the chromosomes of the fetus from a small blood sample. Initially, NIPTs were targeted at detecting trisomy 21 (Down syndrome): meanwhile there are sequencing techniques capable of analysing the entire genome of the unborn child. These yield findings of unclear relevance for the child's future life, resulting in new responsibility structures and dilemmas for the parents-to-be.The industry's marketing strategies overemphasize the benefits of the tests while disregarding their consequences. This paper chooses the opposite path: starting with the underestimated consequences, it focuses on adverse developments and downsides. Disparities, paradoxes, and risks associated with NIPTs are illustrated, ethical conflicts described. Indications that new technologies developed to solve problems create new ones are examined. In the sense of critical thinking, seemingly robust knowledge is scrutinized for uncertainties and ambiguities. It analyses how the interplay between genetic knowledge and social discourse results in new dimensions of responsibility not only for parents-to-be, but also for decision-makers, authorities, and professional societies, illustrated by a review of different national policies and implementation programmes. As shown by the new NIPT policy in Norway, the consequences can be startling. Finally, a lawsuit in the United States illustrates how an agency can risk forfeiting its legitimation in connection with the inaccuracy of NIPTs.

Drug exposure during pregnancy: Current understanding and approaches to measure maternal-fetal drug exposure

Prescription drug use is prevalent during pregnancy, yet there is limited knowledge about maternal-fetal safety and efficacy of this drug use because pregnant individuals have historically been excluded from clinical trials. Underrepresentation has resulted in a lack of data available to estimate or predict fetal drug exposure. Approaches to study fetal drug pharmacology are limited and must be evaluated for feasibility and accuracy. Anatomic and physiological changes throughout pregnancy fluctuate based on gestational age and can affect drug pharmacokinetics (PK) for both mother and fetus. Drug concentrations have been studied throughout different stages of gestation and at or following delivery in tissue and fluid biospecimens. Sampling amniotic fluid, umbilical cord blood, placental tissue, meconium, umbilical cord tissue, and neonatal hair present surrogate options to quantify and characterize fetal drug exposure. These sampling methods can be applied to all therapeutics including small molecule drugs, large molecule drugs, conjugated nanoparticles, and chemical exposures. Alternative approaches to determine PK have been explored, including physiologically based PK modeling, in vitro methods, and traditional animal models. These alternative approaches along with convenience sampling of tissue or fluid biospecimens can address challenges in studying maternal-fetal pharmacology. In this narrative review, we 1) present an overview of the current understanding of maternal-fetal drug exposure; 2) discuss biospecimen-guided sampling design and methods for measuring fetal drug concentrations throughout gestation; and 3) propose methods for advancing pharmacology research in the maternal-fetal population.

A dPCR-NIPT assay for detections of trisomies 21, 18 and 13 in a single-tube reaction-could it replace serum biochemical tests as a primary maternal plasma screening tool?

Background

The next generation sequencing (NGS) based non-invasive prenatal test (NIPT) has outplayed the traditional serum biochemical tests (SBT) in screen of fetal aneuploidies with a high sensitivity and specificity. However, it has not been widely used as a primary screen tool due to its high cost and the cheaper SBT is still the choice for primary screen even with well-known shortages in sensitivity and specificity. Here, we report a multiplex droplet digital PCR NIPT (dPCR-NIPT) assay that can detect trisomies 21, 18 and 13 (T21, T18 and T13) in a single tube reaction with a better sensitivity and specificity than the SBT and a much cheaper price than the NGS-NIPT.

Methods

In this study, the dPCR-NIPT assay’s non-clinical characteristics were evaluated to verify the cell free fetal DNA (cffDNA) fraction enrichment efficiencies, the target cell free DNA (cfDNA) concentration enrichment, the analytical sensitivity, and the sample quality control on the minimum concentration of cfDNA required for the assay. We validated the clinical performance for this assay by blindly testing 283 clinical maternal plasma samples, including 36 trisomic positive samples, from high risk pregnancies to access its sensitivity and specificity. The cost effectiveness of using the dPCR-NIPT assay as the primary screen tool was also analyzed and compared to that of the existing contingent strategy (CS) using the SBT as the primary screen tool and the strategy of NGS-NIPT as the first-tier screen tool in a simulating situation.

Results

For the non-clinical characteristics, the sample processing reagents could enrich the cffDNA fraction by around 2 folds, and the analytical sensitivity showed that the assay was able to detect trisomies at a cffDNA fraction as low as 5% and the extracted cfDNA concentration as low as 0.2 ng/μL. By testing the 283 clinical samples, the dPCR-NIPT assay demonstrated a detection sensitivity of 100% and a specificity of 95.12%. Compared to the existing CS and the NGS-NIPT as the first-tier screen strategy, dPCR-NIPT assay used as a primary screen tool followed by the NGS-NIPT rescreen is the most economical approach to screen pregnant women for fetal aneuploidies without sacrificing the positive detection rate.

Conclusion

This is the first report on a dPCR-NIPT assay, consisting of all the necessary reagents from sample processing to multiplex dPCR amplification, can detect T21, T18 and T13 in a single tube reaction. The study results reveal that this assay has a sensitivity and specificity superior to the SBT and a cost much lower than the NGS-NIPT. Thus, from both the test performance and the economic benefit points of views, using the dPCR-NIPT assay to replace the SBT as a primary screen tool followed by the NGS-NIPT rescreen would be a better approach than the existing CS for detection of fetal aneuploidies in maternal plasma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03455-y.