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Trends in Down’s syndrome live births and antenatal diagnoses in England and Wales from 1989 to 2008: analysis of data from the National Down Syndrome Cytogenetic Register

BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b3794 (Published 27 October 2009) Cite this as: BMJ 2009;339:b3794
  1. Joan K Morris, professor of medical statistics,
  2. Eva Alberman, emeritus professor
  1. 1Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ
  1. Correspondence to: J K Morris j.k.morris{at}qmul.ac.uk
  • Accepted 13 July 2009

Abstract

Objectives To describe trends in the numbers of Down’s syndrome live births and antenatal diagnoses in England and Wales from 1989 to 2008.

Design and setting The National Down Syndrome Cytogenetic Register holds details of 26488 antenatal and postnatal diagnoses of Down’s syndrome made by all cytogenetic laboratories in England and Wales since 1989.

Interventions Antenatal screening, diagnosis, and subsequent termination of Down’s syndrome pregnancies.

Main outcome measures The number of live births with Down’s syndrome.

Results Despite the number of births in 1989/90 being similar to that in 2007/8, antenatal and postnatal diagnoses of Down’s syndrome increased by 71% (from 1075 in 1989/90 to 1843 in 2007/8). However, numbers of live births with Down’s syndrome fell by 1% (752 to 743; 1.10 to 1.08 per 1000 births) because of antenatal screening and subsequent terminations. In the absence of such screening, numbers of live births with Down’s syndrome would have increased by 48% (from 959 to 1422), since couples are starting families at an older age. Among mothers aged 37 years and older, a consistent 70% of affected pregnancies were diagnosed antenatally. In younger mothers, the proportions of pregnancies diagnosed antenatally increased from 3% to 43% owing to improvements in the availability and sensitivity of screening tests.

Conclusions Since 1989, expansion of and improvements in antenatal screening have offset an increase in Down’s syndrome resulting from rising maternal age. The proportion of antenatal diagnoses has increased most strikingly in younger women, whereas that in older women has stayed relatively constant. This trend suggests that, even with future improvements in screening, a large number of births with Down’s syndrome are still likely, and that monitoring of the numbers of babies born with Down’s syndrome is essential to ensure adequate provision for their needs.

Footnotes

  • Contributors: JM is Director of the National Down Syndrome Cytogenetic Register and is responsible for the data and the analysis presented and worked jointly with EA in the writing of this paper. Haiyan Wu, Annabelle Stapleton, and Khadeeja Wahid maintain the National Down Syndrome Cytogenetic Register database. JM is the guarantor for the study.

  • Funding: The NHS Fetal Anomaly Screening Programme funded the National Down Syndrome Cytogenetic Register to collect the data until March 2009. The funders played no role in the analysis or write up of this paper. JM and EA are independent of the Fetal Anomaly Screening Programme. JM and EA had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

  • Data sharing: no additional data available.

  • Competing interests: None declared.

  • Ethical approval: The National Down Syndrome Cytogenetic Register (as part of the British Isles Network of Congenital Anomaly Registers) has multicentre research ethics committee approval from Trent MREC. It was granted section 60 class support under the Health and Social Care Act 2001 for the collection of personal information without consent.

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