Epidemiology underpinning research in the aetiology of orofacial clefts.

INTRODUCTION: Epidemiological information gathered through birth defects surveillance is an important adjunct to carrying out clinical and aetiological research. Information on the incidence in the population, causative risk factors and providing baseline data prior to intervention are all important elements. Under the auspices of the World Health Organisation, it was agreed that a global registry and database on craniofacial anomalies should be created and this, the International Database on Craniofacial Anomalies (ICDFA) was designed to gather information on craniofacial abnormalities from existing birth defects registries and databases around the world to become a resource underpinning research. There are currently 62 registries covering 2 million births per year contributing to a database along with information on the size and type of studies used to collect the information, any variation in ascertainment and on the inclusion of syndromes and associated abnormalities. GENERATION OF HYPOTHESES: From the epidemiological data collected it is possible to carry out meta-analysis and to search for trends and consistencies in the data that enable hypothesis to be generated. Issues such as geographical distribution, ethnicity, gender, associated abnormalities and clefts in stillbirths can all be examined in a meta-analytical approach. Collection of information on risk factors such as maternal illnesses, medications, lifestyle factors, nutrition and perhaps occupational exposures enables investigation into environmental contribution to causality and genetic predisposition. A range of techniques are currently being used to identify new candidate genes and ultimately it will be necessary to test genetic and environmental hypothesis in the context of human population studies.
CONCLUSIONS: It is only by consistency of association between different populations with different gene pools and maternal exposures, lifestyles, nutrition etc that conclusive evidence regarding causality will be found. It is therefore essential, and a major objective of the WHO that international multicentre collaborative studies are setup to gather the appropriate evidence and improve knowledge and the cause of birth defects in general and orofacial clefts in particular, with the ultimate humanitarian and scientific objective of the WHO being primary prevention. CLINICAL UTILITY AND IMPLICATIONS: This IDCFA project fulfils three basic objectives namely to enable global surveillance of CFA; to create online access to those who wish to contribute to the IDCFA, and to develop an online directory of resources on craniofacial anomalies for the support of research and improving quality of care. The next steps for IPDTOC are to expand the number of participating registries and to actively collect data on other craniofacial birth defects.