Contingent prenatal screening for frequent aneuploidies with cell-free fetal DNA analysis

The implementation and impact of non-invasive prenatal testing (NIPT) for Down's syndrome into antenatal screening programmes: A systematic review and meta-analysis

BACKGROUND

Non-invasive prenatal testing (NIPT) is a widely adopted maternal blood test that analyses foetal originating DNA to screen for foetal chromosomal conditions, including Down's syndrome (DS). The introduction of this test, which may have implications for important decisions made during pregnancy, requires continual monitoring and evaluation. This systematic review aims to assess the extent of NIPT introduction into national screening programmes for DS worldwide, its uptake, and impact on pregnancy outcomes.

METHODS AND FINDINGS

The study protocol was published in PROSPERO (CRD42022306167). We systematically searched MEDLINE, CINAHL, Scopus, and Embase for population-based studies, government guidelines, and Public Health documents from 2010 onwards. Results summarised the national policies for NIPT implementation into screening programmes geographically, along with population uptake. Meta-analyses estimated the pooled proportions of women choosing invasive prenatal diagnosis (IPD) following a high chance biochemical screening result, before and after NIPT was introduced. Additionally, we meta-analysed outcomes (termination of pregnancy and live births) amongst high chance pregnancies identified by NIPT. Results demonstrated NIPT implementation in at least 27 countries. Uptake of second line NIPT varied, from 20.4% to 93.2% (n = 6). Following NIPT implementation, the proportion of women choosing IPD after high chance biochemical screening decreased from 75% (95% CI 53%, 88%, n = 5) to 43% (95%CI 31%, 56%, n = 5), an absolute risk reduction of 38%. A pooled estimate of 69% (95% CI 52%, 82%, n = 7) of high chance pregnancies after NIPT resulted in termination, whilst 8% (95% CI 3%, 21%, n = 7) had live births of babies with DS.

CONCLUSIONS

NIPT has rapidly gained global acceptance, but population uptake is influenced by healthcare structures, historical screening practices, and cultural factors. Our findings indicate a reduction in IPD tests following NIPT implementation, but limited pre-NIPT data hinder comprehensive impact assessment. Transparent, comparable data reporting is vital for monitoring NIPT's potential consequences.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Identification of genetic alterations in couples and their products of conceptions from recurrent pregnancy loss in North Indian population

Background: Recurrent pregnancy loss (RPL) is one of the most common pregnancy-related complications, which can be stressful and emotionally draining for a couple. Genetic alterations, which are responsible for RPL, can be present in either of the three genomes: mother, father, or their fetuses. In addition, environmental factors interacting with these three genomes can affect germline cells. With this aim, the present study was conducted to understand the underlying etiology of RPL using Next-generation sequencing (NGS; couple exome and TRIO exomes) in combination with cytogenetic tests [karyotyping and chromosomal microarray (CMA)]. Material & Methods: In present study we recruited 61 couples with RPL (history of ≥ 2 abortions) and 31 products of conceptions (POCs). For all couples karyotyping was done at the time of recruitment, followed by collection of POC samples and parental blood samples. Before processing POC samples for CMA, they were checked for maternal cell contamination (MCC) by QF-PCR. In POC samples with no pathogenic variant, TRIO exome sequencing was done. Further, in case of unavailability of POC sample, couple exome sequencing was done for RPL couples. Results: In six individuals out of 61 couples (5%), abnormality in karyotypes was detected. Among 116 normal karyotypes, there were 11 heteromorphisms (9.5%), for which the couples had to be counselled and reassured. Out of the 31 POCs, 10 were excluded because of MCC (around 30%) and one had major aneuploidy. CMA in POCs identified pathogenic copy number variations (CNVs) in 25% of cases (5/20) and variant of unknown significance (VUS) in 20% of cases (4/20). Autosomal trisomy was the most frequent chromosomal abnormality diagnosed. NGS was performed to establish single-gene causes of RPL. Couple exome sequencing was performed in 20 couples, and 14 were found to be carriers for autosomal recessive conditions. A total of 50 potential disease-causing variants in 40 genes were identified in 33 of 40 individuals (82.5%). Putative causative variants were identified in 37.5% of the TRIO cases (3/8). Mutations in few important genes (SRP54, ERBB4, NEB, ALMS, ALAD, MTHFR, F5, and APOE), which are involved in vital pathways, early embryonic development, and fetal demise, were identified in the POCs. Conclusion: It enhances our understanding of prenatal phenotypes of many Mendelian disorders. These mutated genes may play an auxiliary role in the development of treatment strategies for RPL. There was no correlation of the number of abortions with etiological yield of any technique to detect the cause of RPL. This study shows the utilization of combination of techniques in improving our understanding of the cause of early embryonic lethality in humans.