1. Department of Obstetrics and Gynecology (T.S.M., P.T., O.Y.), Helsinki University Hospital, 00029 Helsinki, Finland
2. Folkhälsan Research Center (T.S.M.), 00250 Helsinki, Finland
3. EPID Research Oy (H.L., P.K., F.H., P.V.), 02130 Espoo, Finland
4. National Institute for Health and Welfare (M.G.), 00271 Helsinki, Finland
5. Nordic School of Public Health (M.G.), 40242 Gothenburg, Sweden