Perinatal epidemiology has become a still larger part of the Department's research programme. Whereas part of the programme focuses on identifying and documenting causes of diseases during pregnancy and early childhood, much research is directed to the impact of exposures during pregnancy and early childhood for occurrence of disease in adolescence and adult life. A number of studies within this programme benefit from the existence of old, nationwide registries, and in particular the possibility of performing large historical follow-up studies. A great asset to the Department is the creation of the Danish National Birth Cohort Better (DNBC) This project contains detailed information on exposure data as well as biological material from 100,000 pregnant women and their offspring. Exposures of particular interest to the department's programme are infections, vaccinations, hormonal products and dietary factors. The DNBC is an open data source and applications for data withdrawal may be posted with the cohort Steering Committee.