Noninvasive Prenatal Screening for Common Fetal Aneuploidies Using Single-Molecule Sequencing

Amplification biases caused by next-generation sequencing (NGS) for noninvasive prenatal screening (NIPS) may be reduced using single-molecule sequencing (SMS), during which PCR is omitted. Therefore, the performance of SMS-based NIPS was evaluated. We used SMS-based NIPS to screen for common fetal aneuploidies in 477 pregnant women. The sensitivity, specificity, positive predictive value, and negative predictive value were estimated. The GC-induced bias was compared between the SMS- and NGS-based NIPS methods. Notably, a sensitivity of 100% was achieved for fetal trisomy 13 (T13), trisomy 18 (T18), and trisomy 21 (T21). The positive predictive value was 46.15% for T13, 96.77% for T18, and 99.07% for T21. The overall specificity was 100% (334/334). Compared with NGS, SMS (without PCR) had less GC bias, a better distinction between T21 or T18 and euploidies, and better diagnostic performance. Overall, our results suggest that SMS improves the performance of NIPS for common fetal aneuploidies by reducing the GC bias introduced during library preparation and sequencing.

Negotiating Awareness: Dutch Midwives' Experiences of Noninvasive Prenatal Screening Counseling

BACKGROUND

Discussion of the topic of noninvasive prenatal screening (NIPS) has become a standard part of Dutch maternity care practice. This means that pregnant women who are contemplating NIPS can receive counseling from their midwife or obstetrician. The aim of this study is to understand the communicative practices and decision-making principles regarding first-tier use of NIPS, as experienced by Dutch midwives.

METHODS

Qualitative analysis of in-depth interviews with Dutch midwives (n = 10) exploring their conversations about NIPS counseling and decision making.

RESULTS

Midwives value the autonomy of women in decisions on NIPS. They consider it a midwifery task to assess women's awareness of the risks and implications of using or not using this mode of screening. The optimal level of awareness may differ between women and midwives, creating novel challenges for informed decision making in midwifery communication.

KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Negotiating awareness about NIPS in individual women is a relatively new and complex midwifery task in need of counseling time and skill. NIPS practices call for a reflection on midwifery values in the context of integrated maternity care.

Diagnostic cytogenetic testing following positive noninvasive prenatal screening results of sex chromosome abnormalities: Report of five cases and systematic review of evidence

BACKGROUND

Follow-up cytogenetic analysis has been recommended for cases with positive noninvasive prenatal screening (NIPS) results. This study of five cases with numerical and structural sex chromosomal abnormalities (SCA) and a review of large case series of NIPS provided guidance to improve prenatal diagnosis for SCA.

METHODS

Following positive NIPS results for SCA, karyotype analysis, chromosomal microarray analysis (CMA), fluorescence in situ hybridization (FISH), and locus-specific quantitative PCR were performed on cultured amniocytes, chorionic villi cells, and stimulated lymphocytes. Review of large case series was performed to evaluate the NIPS positive rate, follow-up rate of cytogenetic analysis, positive predictive value (PPV) for major types of SCA, and relative frequencies of subtypes of major SCA.

RESULTS

Of the five cases with positive NIPS for SCA, case 1 showed a mosaic pattern of monosomy X and isodicentric Y; case 2 showed a mosaic pattern of monosomy X confined to the placenta; cases 3 and 4 had an isochromosome of Xq, and case 5 showed a derivative chromosome 14 from a Yq/14p translocation of maternal origin. Review of literature showed that mean positive rate of NIPS for SCA was 0.61%, follow-up rate of cytogenetics analysis was 76%, and mean PPV for SCA was 48%. Mosaic patterns and structural rearrangements involving sex chromosomes were estimated in 3%-20% and 3% of SCA cases, respectively.

CONCLUSION

These five cases further demonstrated the necessity to pursue follow-up cytogenetic analysis to characterize mosaic patterns and structural abnormalities involving sex chromosomes and their value for prenatal genetic counseling. A workflow showing the performance of current NIPS and cytogenetic analysis for SCA was summarized. These results could facilitate an evidence-based approach to guide prenatal diagnosis of SCA.

Evaluation of Noninvasive Prenatal Testing (NIPT) guidelines using the AGREE II instrument

Objective: The rapid increase of cell-free fetal DNA analysis for Down syndrome screening requires evidence-based clinical practice guidelines for noninvasive prenatal testing (NIPT). Several studies show that the quality of many guidelines is low and there are still many health areas where this quality is not systematically evaluated. Given the absence of research, in the NIPT field, we used an internationally validated tool to evaluate a set of three NIPT practice guidelines and to look at dimensions that can be improved.Methods: Four appraisers, experts in prenatal screening, evaluated three main NIPT guidelines published in the last 2 years using the AGREE II (Appraisal of Guidelines for Research and Evaluation II), a tool specifically designed for guideline quality appraisal.Results: Guidelines scored higher in domains related with scope, purpose, and clarity of presentation, and lower in stakeholder involvement and rigor of development. Intradomain items evaluation showed asymmetries between guidelines. The UK-NSC was the guideline with the best scores.Discussion: Several areas of NIPT guidelines, such as stakeholders involvement, selection of supporting evidence, external reviews, updating processes, and competing interests disclosure, can be improved. Appraisers recommend modifications to all NIPT guidelines that can lead to substantial improvements in their methodological quality and subsequently make a contribution to prenatal screening improvement.