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Impact of a new national screening policy for Down's syndrome in Denmark: population based cohort study
Charlotte K Ekelund1, Finn Stener Jørgensen, Olav Bjørn Petersen
1Department of Fetal Medicine, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen, Denmark.
Insights
A new first-trimester screening strategy in Denmark significantly reduced Down
Area of Science:
- Prenatal diagnostics and screening
- Fetal medicine and obstetrics
- Genetics and congenital disorders
Background:
- Down's syndrome screening has evolved with advancements in prenatal diagnostic techniques.
- First-trimester screening offers an early opportunity for risk assessment.
- Denmark implemented a national first-trimester screening strategy to improve outcomes.
Purpose of the Study:
- To assess the impact of Denmark's first-trimester screening strategy (2004-2006) on Down's syndrome births.
- To evaluate changes in chorionic villus sampling (CVS) and amniocentesis rates.
- To determine detection and false positive rates for the screening program.
Main Methods:
- Population-based cohort study involving 19 Danish departments.
- Analysis of data from 65,000 pregnancies annually between 2000-2007.
- Primary outcomes: Down's syndrome diagnoses (prenatal/postnatal), CVS, and amniocentesis numbers.
Main Results:
- Infants born with Down's syndrome decreased from 55-65 annually (2000-2004) to 31 (2005) and 32 (2006).
- Total CVS and amniocenteses dropped from 7524 (2000) to 3510 (2006).
- Detection rates were 86% (2005) and 93% (2006); false positive rates were 3.9% (2005) and 3.3% (2006).
Conclusions:
- National first-trimester screening in Denmark effectively halved the number of infants born with Down's syndrome.
- The strategy significantly reduced invasive procedures like CVS and amniocentesis.
- Early implementation of the policy demonstrated substantial positive impacts on public health.
Objectives:
To evaluate the impact of a screening strategy in the first trimester, introduced in Denmark during 2004-6, on the number of infants born with Down's syndrome and the number of chorionic villus samplings and amniocenteses, and to determine detection and false positive rates in the screened population in 2005 and 2006.
Design:
Population based cohort study.
Setting:
19 Danish departments of gynaecology and obstetrics and a central cytogenetic registry 2000-7.
Participants:
65 000 pregnancies per year.
Main Outcome Measures:
The primary outcomes measured were number of fetuses and newborn infants with Down's syndrome diagnosed prenatally and postnatally and number of chorionic villus samplings and amniocenteses carried out. Secondary outcomes measured were number of women screened in 2005 and 2006, screen positive rate, and information on screening in 2005 and 2006 for infants with a postnatal diagnosis of Down's syndrome.
Results:
The number of infants born with Down's syndrome decreased from 55-65 per year during 2000-4 to 31 in 2005 and 32 in 2006. The total number of chorionic villus samplings and amniocenteses carried out decreased from 7524 in 2000 to 3510 in 2006. The detection rate in the screened population in 2005 was 86% (95% confidence interval 79% to 92%) and in 2006 was 93% (87% to 97%). The corresponding false positive rates were 3.9% (3.7% to 4.1%) and 3.3% (3.1% to 3.4%).
Conclusion:
The introduction of a combined risk assessment during the first trimester at a national level in Denmark halved the number of infants born with Down's syndrome. The strategy also resulted in a sharp decline in the number of chorionic villus samplings and amniocenteses carried out, even before full implementation of the policy.
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