1. Department of Epidemiology and Biostatistics School of Public Health, Imperial College London London UK
2. Department of Epidemiology Research Statens Serum Institut Copenhagen Denmark
3. Department of Clinical Medicine University of Copenhagen Copenhagen Denmark
4. Department of Medicine Stanford University School of Medicine Stanford California USA
5. Centre for Fertility and Health Norwegian Institute of Public Health Oslo Norway
6. K.G. Jebsen Center for Genetic Epidemiology Norwegian University of Science and Technology Trondheim Norway