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Objectives: The primary aim of this study was to compare the screening performance for trisomy 21 (T21) between combined first-trimester screening (cFTS) with referral for invasive testing at a T21 risk ≥ 1 in 300, and contingent screening consisting of referral for invasive testing at a cFTS-T21 risk ≥ 1 in 100 and referral for cell-free DNA (cfDNA) testing at a cFTS-T21 risk between 1 in 100 and 1 in 1000. Secondary aims were to compare the incidence of fetuses diagnosed with trisomy 18 (T18), trisomy 13 (T13) or sex chromosome aneuploidy, and examine the association between fetal fraction of cfDNA in maternal blood and maternal/fetal characteristics., Methods: Women with a singleton pregnancy and a cFTS-T21 risk of ≥ 1 in 1000 were recruited consecutively from two Danish hospitals between August 2014 and May 2015. First-trimester combined screening was based on maternal age, nuchal translucency thickness and levels of pregnancy-associated plasma protein A (PAPP-A) and β-human chorionic gonadotropin (β-hCG). Blood samples for cfDNA testing were analyzed for risks of T21, T18, T13 and sex chromosomal aneuploidies. cfDNA analysis was conducted blinded to the cFTS assessment and karyotype results. Pregnancy outcomes and pre- and postnatal karyotypes were obtained from the Danish Fetal Medicine Database., Results: Among 6449 women who underwent cFTS risk assessment, 869 (13.5%) had a T21 risk of ≥ 1 in 1000 and 597 were included for cfDNA testing. Among these, there were 15 cases of T21, one case of T18 and two cases of T13. The sensitivity for detection of T21 was 100% using both screening strategies, while specificity increased significantly (P < 0.0001) from 97.0% using the cFTS strategy to 98.8% using the contingent approach. The sensitivity for detection of T21, T18 and T13 increased from 94.4% using the cFTS strategy to 100% using the contingent approach, with overlapping CIs, while specificity increased significantly (P < 0.0001) from 97.1% for cFTS to 98.9% for the contingent strategy. Seven pregnancies were categorized as being at increased risk of a sex chromosomal aneuploidy by cfDNA testing but chromosome analysis was discordant, corresponding to a false-positive rate of 1.2%. The fetal fraction decreased significantly with increasing maternal weight and increased significantly with the level of β-hCG and PAPP-A and among female fetuses, in both univariate and multivariate analyses., Conclusions: In a clinical setting with efficient cFTS, contingent screening offering women with a cFTS risk of ≥ 1 in 100 an invasive test and women with a risk from 1 in 100 to 1 in 1000 a cfDNA test had the same sensitivity for T21, T18 and T13, but significantly increased specificity, when compared with offering an invasive test to all women with a risk of ≥ 1 in 300. Implementing contingent screening would therefore reduce significantly the number of invasive tests performed at no loss of sensitivity. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd., (Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.)

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., (© 2017 Nordic Federation of Societies of Obstetrics and Gynecology.)

Introduction: The aim was to investigate the parental decisions about prenatal screening and diagnosis among infants with trisomy 21 (T21) in a national cohort with high uptake of combined first-trimester screening (cFTS)., Material and Methods: This was a nationwide population-based study including infants born in 2009-2012. Information from the cFTS, fetal karyotype results and pregnancy outcome was obtained from the Danish Fetal Medicine Database on all women with a cFTS risk assessment. Cut-off for referral for invasive testing was ≥1:300. Karyotype results from pregnancies with no cFTS were obtained from the Danish Cytogenetic Central Registry., Results: The uptake rate of cFTS was 91.6%, and 82.8% (8,032/9,704) of the screen-positive women opted for invasive testing. Overall, 82.2% (454/552) chose to terminate an affected pregnancy. In the 4-year period, 102 of 232,962 singletons were born alive with T21. The cFTS risk was true-positive, false-negative or not obtained in 21.6, 48.0 and 30.4%, respectively, of these pregnancies., Discussion: In this large national cohort, 4.4 per 10,000 live-born infants had T21. Of 102 infants with T21 from 2009 to 2012, 52.0% were born after the women had not opted for cFTS or were true-positive but declined invasive testing or termination, and 48.0% were born after a false-negative risk assessment., (© 2016 S. Karger AG, Basel.)

Objective: The objective of this study was to introduce non-invasive prenatal testing (NIPT) for fetal autosomal trisomies and gender in a Danish public health setting, using semi-conductor sequencing and published open source scripts for analysis., Methods: Plasma-derived DNA from a total of 375 pregnant women (divided into three datasets) was whole-genome sequenced on the Ion Proton™ platform and analyzed using a pipeline based on WISECONDOR for fetal autosomal aneuploidy detection and SeqFF for fetal DNA fraction estimation. We furthermore validated a fetal sex determination analysis., Results: The pipeline correctly detected 27/27 trisomy 21, 4/4 trisomy 18, and 3/3 trisomy 13 fetuses. Neither false negatives nor false positives (chromosomes 13, 18, and 21) were observed in our validation dataset. Fetal sex was identified correctly in all but one triploid fetus (172/173). SeqFF showed a strong correlation (R(2)  = 0.72) to Y-chromosomal content of the male fetus samples., Discussion: We have implemented NIPT into Danish health care using published open source scripts for autosomal aneuploidy detection and fetal DNA fraction estimation showing excellent false negative and false positive rates. SeqFF provides a good estimation of fetal DNA fraction. This coupled with an analysis of fetal sex that provides a complete NIPT workflow, which may easily be adapted for implementation in other public health laboratories. © 2016 John Wiley & Sons, Ltd., (© 2016 John Wiley & Sons, Ltd.)

Objective: To describe the establishment and organization of the Danish Fetal Medicine Database and to report national results of first-trimester combined screening for trisomy 21 in the 5-year period 2008-2012., Design: National register study using prospectively collected first-trimester screening data from the Danish Fetal Medicine Database., Population: Pregnant women in Denmark undergoing first-trimester screening for trisomy 21., Methods: Data on maternal characteristics, biochemical and ultrasonic markers are continuously sent electronically from local fetal medicine databases (Astraia Gmbh software) to a central national database. Data are linked to outcome data from the National Birth Register, the National Patient Register and the National Cytogenetic Register via the mother's unique personal registration number. First-trimester screening data from 2008 to 2012 were retrieved., Main Outcome Measures: Screening performance was assessed for the years 2008-2012 by calculating detection rates and screen-positive rates., Results: A total of 268 342 first-trimester risk assessments for trisomy 21 were performed in singleton pregnancies. Participation rate in first-trimester screening was >90%. The national screen-positive rate increased from 3.6% in 2008 to 4.7% in 2012. The national detection rate of trisomy 21 was reported to be between 82 and 90% in the 5-year period., Conclusion: A national fetal medicine database has been successfully established in Denmark. Results from the database have shown that at a national level first-trimester screening performance for trisomy 21 is high with a low screen-positive rate and a high detection rate., (© 2015 Nordic Federation of Societies of Obstetrics and Gynecology.)

Objectives: In Denmark a new national guideline for prenatal screening and diagnosis was issued in 2004 according to which all pregnant women should be offered a first-trimester combined risk assessment for trisomy 21 (T21). The aim of this study was to investigate whether the new screening strategy for T21 has changed the gestational age at which trisomy 18 (T18) and trisomy 13 (T13) are diagnosed prenatally, and the number of infants born with T18 or T13., Methods: We collected from the Danish Cytogenetic Central Register information on all prenatal and postnatal chromosome analyses for T18 or T13, registered from 1997 to 2007. Information on first-trimester screening results was collected from each department of obstetrics and gynecology performing the nuchal translucency scans. The cut-off used for referral to invasive diagnostic testing for T21 and for T18/T13 was 1 : 300 and 1 : 150 at screening, respectively., Results: In total, there were 435 cases with T18 and 168 cases with T13 between 1997 and 2007 in Denmark. The estimated incidence of T18 and T13 at the time of delivery was calculated as 2.5 and 1.6 per 10 000 deliveries, respectively. The number (proportion) of cases diagnosed before week 18 increased significantly, from 63 (59.4%) in 1997 and 1998 to 90 (80.4%) in 2006 and 2007 (P < 0.001). In addition, the number of T18 and T13 cases diagnosed prenatally after week 22 or postnatally decreased significantly, from 34 (32.1%) in 1997 and 1998 to seven (6.3%) in 2006 and 2007 (P < 0.0001). For women participating in first-trimester risk assessment in 2006 and 2007, the detection rate of T18 and T13 was 78.8% (95% CI, 71.0-86.7%)., Conclusion: The number of T18 and T13 fetuses diagnosed before week 18 increased significantly after the introduction of a combined first-trimester screening strategy for T21 in Denmark. In addition, the total number of fetuses diagnosed late in pregnancy and infants born with T18 or T13 decreased significantly. The national detection rate for T18 and T13 in the first trimester is comparable with detection rates found in modeled datasets and other prospective studies., (Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.)

Introduction: First trimester screening for Down's syndrome was evaluated by the National Board of Health in 2004, and recommended to all pregnant women in the form of an informed choice. We have reviewed prenatal and postnatal chromosome aberrations in 3 counties in Denmark during the years of implementation in 2004, 2005 and 2006., Materials and Methods: Risk evaluation based on combined screening (fetal nuchal translucency measurement and serum screening of the pregnant woman) was introduced in the counties of Copenhagen, Roskilde and Storstrom, covering approximately 1.1 million inhabitants. We registered the number of chorionic villus biopsies (CVS) and amniocenteses (AC), as well as the number of cases with trisomy, triploidy and sex chromosome aberrations found prenatally. We also registered the number of children born with Down's syndrome during the period., Results: The number of CVS/AC decreased from 1382 to 790, or 40%. There was an increase in the number of foetuses diagnosed with trisomy 21: in 2004 trisomy 21 was diagnosed in 12 foetuses, in 2006 the number was 30. The number of children born with Down's syndrome was 10 and 5 in 2004 and 2006, respectively. National figures from the Danish central cytogenetic registry confirm a decrease in children born with Down's syndrome., Conclusion: The implementation of combined screening in 3 counties resulted in a reduction in invasive procedures (chorionic villus samples and amniocenteses) by 40%, which is in accordance with the aims of the National Board of Health. As expected, a significant increase in the number of prenatally diagnosed foetuses with trisomy 21 was observed. The number of children born with Down's syndrome decreased, but the numbers are small. The investigation does not review aspects of organisation or counselling and psychosocial issues.

An abstract of the article "Newborn with Down's syndrome: first trimester screening or not?" by C.B. Miltoft and colleagues is presented.