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Impact of a new national screening policy for Down’s syndrome in Denmark: population based cohort study

BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a2547 (Published 28 November 2008) Cite this as: BMJ 2008;337:a2547
  1. Charlotte K Ekelund, research assistant1,
  2. Finn Stener Jørgensen, consultant2,
  3. Olav Bjørn Petersen, consultant3,
  4. Karin Sundberg, consultant1,
  5. Ann Tabor, professor14
  6. Danish Fetal Medicine Research Group
  1. 1Department of Fetal Medicine, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen, Denmark
  2. 2Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Hvidovre University Hospital, Denmark
  3. 3Department of Obstetrics and Gynaecology, Skejby University Hospital, Aarhus, Denmark
  4. 4Faculty of Health Sciences, University of Copenhagen
  1. Correspondence to: A Tabor ann.tabor{at}rh.regionh.dk
  • Accepted 30 September 2008

Abstract

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.

Footnotes

  • Members of the Danish Fetal Medicine Research Group are: Hans Jakob Andersen, Jeanette Christensen, Vibeke Ersbak, Richard Farlie, Carsten Henriques, Annette Wind Olesen, Anni Holmskov, Lisa Neerup Jensen, Anette Kristiansen, Torben Larsen, Hedvig Poulsen, Jan Ramb, Lillian Skibsted, Peter Skovbo, Steffen Sommer, Lene Sperling, Susanne Vemmelund Juul, Helle Zingenberg. We thank Jan Hansen for retrieval of data from the Danish Central Cytogenetic Registry, Kirsten Rasmussen for retrieval of data from the Genetic Database of Funen, Steen Rasmussen (Danish National Board of Health) for providing gestational age at delivery in cases where no screening was done,and the departments of clinical biochemistry for analysing the biochemical samples used in the screening programme.

  • Contributors: AT and CKE planned and did the study in cooperation with FSJ, OBP, and KS. CKE and AT wrote the manuscript and are guarantors. Hans Jakob Andersen, Jeanette Christensen, Vibeke Ersbak, Richard Farlie, Carsten Henriques, Annette Wind Olesen, Anni Holmskov, Lisa Neerup Jensen, FSJ, Anette Kristiansen, Torben Larsen, OBP, Hedvig Poulsen, Jan Ramb, Lillian Skibsted, Peter Skovbo, Steffen Sommer, Lene Sperling, KS, Susanne Vemmelund Juul and Helle Zingenberg retrieved data from the local Astraia servers and reviewed and accepted the final manuscript.

  • Funding: None.

  • Competing interests: None declared.

  • Ethical approval: This study was approved by the Danish Data Protection Agency and Danish National Board of Health.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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