J Med Genet 42:54-57 doi:10.1136/jmg.2004.023309
  • Medical genetics in practice

An aetiological classification of birth defects for epidemiological research

  1. D Wellesley1,
  2. P Boyd2,
  3. H Dolk3,
  4. S Pattenden4
  1. 1Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton SO16 5YA, UK
  2. 2CAROBB National Perinatal Epidemiology Unit, University of Oxford, Old Campus Road, Headington, Oxford OX3 7LG, UK
  3. 3Faculty of Life and Health Sciences, University of Ulster at Jordanstown, Newtownabbey, Co Antrim BT37 OQB, UK
  4. 4Environmental Epidemiology Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK
  1. Correspondence to:
 Dr D Wellesley
 Head of Prenatal Genetics, Wessex Clinical Genetics Service, Princess Anne Hospital, Coxford Road Southampton SO16 5YA;
  • Received 26 May 2004
  • Accepted 14 July 2004
  • Revised 12 July 2004


Background: Congenital anomaly registers collect data on antenatally and postnatally detected anomalies for surveillance, research, and public health purposes. Each anomaly is coded using the International Statistical Classification of Diseases and Related Health Problems (ICD-9/ICD-10) based on body systems, allowing accurate comparisons between registers for individual anomalies. When commencing an environmental, epidemiological study, it became clear to us that there is no standard classification that takes aetiology into account. This paper describes a new classification for use in studies addressing aetiology.

Method: A classification system was evolved and piloted using cases in a study of geographical variation in congenital anomaly prevalence.1 Cases that were difficult to categorise were noted, and after discussion with a team of experts, the classification was adjusted accordingly.

Results and conclusion: A robust, hierarchical method of classifying birth defects into eight categories has been produced, for use at source of data registration in conjunction with, but independent of, ICD coding.


  • Competing interests: none declared