Why European collaboration?
- Pooling of data.
- Comparison of data.
- Sharing of expertise.
- Joint approach to European public health questions.
Why register congenital anomalies?
There are two main reasons why congenital anomaly registers are established:
- To facilitate the identification of teratogenic exposures. Ever since thalidomide and rubella (german measles) were discovered as powerful teratogens, registries have been set up to facilitate research and surveillance concerning environmental causes of congenital anomalies, and to give early warning of new teratogenic exposures.
Registers are also used for genetic studies, and increasingly for research into the interaction of genetic and environmental factors in causing congenital anomalies. Congenital anomalies are registered not only for their intrinsic importance, but as indicators of other adverse pregnancy outcomes linked to teratogenic exposures such as spontaneous abortions and neurobehavioural outcomes that are not as amenable to surveillance.
- For the planning and evaluation of health services. This includes primary prevention strategies such as periconceptional folic acid supplementation to prevent neural tube defects and vaccination against rubella to prevent congenital rubella syndrome, so-called "secondary prevention" by prenatal screening and diagnosis, and tertiary prevention through paediatric, rehabilitative and other services.
Population-based registries are a particularly powerful tool for the evaluation of health services, because they represent the experience of a whole community, not the outcomes of specialist units which may serve only a selected group of women or children, or which may have atypical human or financial resources.
Many birth defect registries in Europe have been set up to provide a mechanism for the audit of prenatal screening practice. The registry can provide data on the proportion of cases of congenital anomaly diagnosed prenatally, the proportion of positive prenatal screening results which were confirmed as cases of congenital anomaly, and the proportion of prenatally diagnosed cases which led to termination of pregnancy, as well as related information about prenatal screening methods.
How can a Register be used?
Whether concerned with the identification of teratogenic exposures, or with planning and evaluation of health services, or both, registers can be used in two main ways:
- As a basis for surveillance using routinely collected data. Every register routinely collects a core of standard information on each malformed child, and a core of information (often more limited) on non-malformed children in the population.
- As a basis for special or ad-hoc studies, such as case-control studies, requiring further data collection. The presence of a register which has already done the work of identifying who in the population has a congenital anomaly, with details of diagnosis, can greatly facilitate the conduct of ad-hoc studies which seek to address specific hypotheses concerning teratogenic exposures or effectiveness of health services.
The decision as to which data should be included in the routine dataset of a registry, and which data should be collected only in ad-hoc studies is a difficult one. Each data item that is included in the routine dataset uses resources that must be balanced against other uses of those resources. Collection of incomplete and inaccurate data is generally a waste of resources. Depending on local circumstances, it may be justifiable for the registry to concentrate almost entirely on data about the baby and its diagnosis in its routine data collection, leaving most risk factor data for collection in ad-hoc studies.
Some ad-hoc data collection will always be necessary to address new or more elaborate hypotheses. However, registers that do not record the identity of children for confidentiality reasons can experience difficulties in supporting ad-hoc studies effectively and efficiently.
In general, risk factor data must be present for both cases and controls (non-malformed children) in order to be interpretable. While all registers collect basic information about the number of births in their population by type of birth and maternal age, some registers in addition collect the same set of risk factor information on control babies as on case babies in their routine data collection.
There are also useful approaches to analysing risk factor data among malformed cases only, where children with different malformations act as controls for each other in "proportionate" analyses. For example, specific associations between particular drugs and particular malformation types can be sought.
How does EUROCAT function?
- Standard data concerning baby, diagnosis, mother and father (see Guide 1.5).
- Common coding system for standard data (see Guide 1.5).
- Standard computer data entry and validation programme available (see EUROCAT Data Management Software).
- Anonymous data transmitted to the Central Registry which collates the pooled database, and carries out surveillance and research using the common database.
- Annual meetings of Registry Leaders to discuss data standardisation, surveillance and research.
- Steering Committee of elected Registry Leaders and Work Package Leaders.
- Prevalence data tables updated bi-annually with prevalence rates of 96 congenital anomaly subgroups in each Registry, with the number of cases reported among livebirths, stillbirths and terminations of pregnancy following prenatal diagnosis and trends in prevalence since 1980 (see Prevalence Data Tables). Prevalence tables conceived and developed by EUROCAT network 2000-2014.
- Extracts of the common database can be requested by researchers, by submitting a research protocol for approval (see Requesting EUROCAT data).