CONGENITAL ANOMALIES IN THE BRITISH ISLES

The first congenital anomaly register in the British Isles was established in 1949, with a national system for England and Wales introduced in 1969 in the wake of the thalidomide epidemic. There are now 14 regional congenital anomaly registers and three disease-specific registers. These registers involve an extensive local network of notifiers, use multiple sources of case ascertainment, consistent coding, and include cases resulting in termination of pregnancy for fetal anomaly following prenatal diagnosis. They have optimised the coverage, completeness and ascertainment of congenital anomalies within their population, and are therefore able to provide better quality data than the national system. There are notable variations in the prevalence of congenital anomaly subtypes within these regions that cannot be accounted for in terms of differences in case ascertainment or registration practices. This underlying variation in prevalence should be recognised and taken into consideration in the design of epidemiological studies that are investigating the contribution of environmental influences to congenital anomaly risk, to ensure correct interpretation of the findings. Local congenital anomaly register data has been used to investigate congenital anomaly risk in populations within the British Isles living close to landfill sites and incinerators, and to possible contaminants in drinking water. Whilst the inclusion of high quality data from established congenital anomaly registers enhances the quality of outcome data, such studies are currently limited by the lack of detailed information on exposure. Causal pathways will only be determined if future studies combine high quality congenital anomaly data with increased information on exposure assessment.