National data on the early clinical use of non-invasive prenatal testing in public and private healthcare in Denmark 2013-2017.

INTRODUCTION: In Denmark, non-invasive prenatal testing (NIPT) has been used since 2013. We aimed to evaluate the early clinical use of NIPT in Danish public and private healthcare settings before NIPT became an integrated part of the national guidelines on prenatal screening and diagnosis in 2017. MATERIAL AND METHODS: NIPT data were collected between March 2013 and June 2017 from national public registries and private providers. Results from follow-up samples (chorionic villi, amniotic fluid, postnatal blood or fetal tissue) were included from The Danish Cytogenetics Central Registry and indications and outcome from The Danish Fetal Medicine Database. RESULTS: A total of 3936 NIPT results were included in the study from public hospitals (n = 3463, 88.0%) and private clinics (n = 473, 12.0%). The total number of prenatal tests was 19 713 during the study period: 20% were NIPT analyses (n = 3936) and 80% invasive procedures (n = 15 777). Twenty-five percent of NIPTs in the private clinics were performed before gestational week 11+0 , whereas NIPT in public settings was used only after combined first trimester screening (P < .001). Regardless of indication, the national public sensitivity was 96.9% (95% CI 82.0%-99.8%) for trisomy 21, 100% (95% CI 46.3%-100%) for trisomy 18, 100% (95% CI 5.5%-100%) for trisomy 13, and 87.0% (95% CI 74.5%-92.4%) for any fetal chromosomal aberration. Forty-seven true-positive NIPT results included cases of common aneuplodies (trisomy 21, n = 31; trisomy 18, n = 5; and trisomy 13, n = 1), sex chromosomal aberrations (n = 7) and atypical chromosomal aberrations (n = 3). One false-negative NIPT result occurred (trisomy 21). Of 47 cases, 21 (45%) cases with a true-positive NIPT result resulted in live births by choice; 11 of these children had Down and 4 had Edwards syndrome. CONCLUSIONS: The total number of NIPT analyses was low compared with the number of invasive procedures in the implementation period. In contrast to the generally high termination rate after a positive result following invasive testing in Denmark, a high proportion of true-positive NIPT results from the public setting resulted in live births. NIPT may be an important risk-free alternative to invasive testing for a minority of women in the public setting who wish to use prenatal genetic testing for information only and not for reproductive decision-making.

Prevalence of mosaicism in uncultured chorionic villus samples after chromosomal microarray and clinical outcome in pregnancies affected by confined placental mosaicism.

OBJECTIVE: To evaluate the prevalence of mosaicism in chorionic villus sampling (CVS) samples after chromosomal microarray (CMA) and clinical outcome of pregnancies affected by confined placental mosaicism. METHOD: We retrieved all results from CMA, array-based comparative genomic hybridization, on CVS samples from January 2011 to November 2017 from Central and North Denmark Regions. Mosaic results from uncultured chorionic villi, cytotrophoblasts and mesenchymal cells, after CVS and follow-up on amniocytes, fetal tissue, or postnatal blood were studied and matched with clinical data from The Danish Fetal Medicine Database. RESULTS: Prevalence of mosaicism was 93 out of 2,288 (4.1%) CVS samples of which 17 (18.3%) concerned submicroscopic copy number variations (CNVs) <10 Mb. Follow-up analyses were performed in 62 cases. True fetal mosaicism (TFM) was confirmed in 18.4% (7/38) when mosaicism involved whole chromosome aneuploidy and in 25.0% (6/24), when involving a CNV (P = .59). Median birth weight z-score was higher in cases of confined placental mosaicism for a CNV (0.21) than cases involving whole chromosomes (-0.74) (P = .02). CONCLUSION: Prevalence of mosaicism in CVS samples is higher after CMA on uncultured tissue than after conventional karyotyping on cultured tissue. The risk of TFM is equally high in cases of mosaicism for CNVs and whole chromosomes.

National screening guidelines and developments in prenatal diagnoses and live births of Down syndrome in 1973-2016 in Denmark.

INTRODUCTION: Denmark was the first country in the world to implement a national, free-for-all offer of prenatal screening for Down syndrome to all pregnant women. It has a high uptake (>90%) compared to other countries. Thus, Denmark offers an interesting case for investigating the consequences of implementing comprehensive, national prenatal screening guidelines. The aim of this study was to describe the historical developments in invasive procedures, pre-/postnatal diagnoses of Down syndrome and Down syndrome live births in the period 1973-2016 in Denmark. MATERIAL AND METHODS: Data on invasive procedures, pre- and postnatal Down syndrome diagnoses were retrieved from the Danish Cytogenetic Central Registry. RESULTS: From 1973 to 1993, screening based on maternal age and high-risk indications resulted in a constant increase in invasive procedures. After the introduction of the triple test in 1994, invasive procedures decreased for the first time in 20 years. Following the introduction of an offer of combined screening to all pregnant women in 2004, the number of invasive procedures decreased markedly, while there was a concurrent increase in prenatal diagnoses of Down syndrome. Additionally, the number of Down syndrome live births decreased suddenly and significantly, but subsequently stabilized at 23-35 annual live births. Of these, the majority were diagnosed postnatally. CONCLUSION: Though prenatal screening technologies constantly improve, it was the introduction of and adherence to national guidelines that resulted in marked shifts in screening procedures and outcome in Denmark.