Spatial investigation of congenital malformations in Reunion Island (2008-2012)

International audienceBackground: Reunion Island is a French territory located in the south- western Indian Ocean. The Reunion Registry of congenital malformations is in charge of monitoring cases. Overall prevalence (289 cases per 10,000 births) is close to the average reported by mainland French registries (315 cases). However, the prevalence of spina bifida is almost twice (10 cases per 10,000 births) the one reported in mainland France (5 cases). This study aims to describe the spatial distribution of different birth defects and identifying clusters.Methods: The analysis specifically tackles three groups being potentially related to environmental exposure. Each case recorded between 2008 and 2012 was geolocated according to its home address: 492 cases of congenital heart defects, 108 cases of cleft lip and palate and 69 cases of spina bifida. Four statistical methods were applied at different administrative scales: Standardized Prevalence Ratio (SPR), Hierarchical Clus- ter Analysis (HCA), Kulldorff method and Geographic epicenter method.Results: The resulting clusters differ depending on the method. Combining the observation at different administrative scales helps to identify the most affected areas for each pathology.Conclusions: These initial observations allow considering case-control studies to identify exposure factors in the most affected areas, including environmental, socio-economic and healthcare factors