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Published 26 October 2009, doi:10.1136/bmj.b3794
Cite this as: BMJ 2009;339:b3794
Joan K Morris, professor of medical statistics, Eva Alberman, emeritus professor
1 Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ
Correspondence to: J K Morris j.k.morris{at}qmul.ac.uk
Design and setting The National Down Syndrome Cytogenetic Register holds details of 26488 antenatal and postnatal diagnoses of Downs syndrome made by all cytogenetic laboratories in England and Wales since 1989.
Interventions Antenatal screening, diagnosis, and subsequent termination of Downs syndrome pregnancies.
Main outcome measures The number of live births with Downs syndrome.
Results Despite the number of births in 1989/90 being similar to that in 2007/8, antenatal and postnatal diagnoses of Downs syndrome increased by 71% (from 1075 in 1989/90 to 1843 in 2007/8). However, numbers of live births with Downs 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 Downs 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 Downs 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 Downs syndrome are still likely, and that monitoring of the numbers of babies born with Downs syndrome is essential to ensure adequate provision for their needs.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.
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