The East Flanders Prospective Twin Survey: The Methodology of a Population-Based Registry With Biobank

The East Flanders Prospective Twin Survey, established in 1964, is one of the longest running twin birth registries with known placentation in the world. It operates across 13 maternity hospitals in East Flanders, Belgium, and has already registered 10,787 twin pairs and 318 triplet sets. Using a standardized protocol, EFPTS prospectively collects perinatal and biological data at birth, including detailed placental examination, systematic clinical documentation, and biobanking. Longitudinal follow-up and integration with national health and environmental databases enable linkage of early-life data to later-life phenotypes. Enrichment through nationwide datasets, such as the Study Centre for Perinatal Epidemiology, Child and Family health centers, environmental databases (based on land cover data and national monitoring stations), the Belgian National Register, and genomic reference data, further expands research opportunities. With over 60 years of experience, the EFPTS provides a uniquely rich and reliable framework for investigating the (epi)genetic and environmental determinants of health and disease.