1. Section for Epidemiology; Department of Public Health; Aarhus University; Aarhus Denmark
2. Department of Epidemiology and Social Science on Reproductive Health; Shanghai Institute of Planned Parenthood Research; WHO Collaborating Center for Research in Human Reproduction; National Population & Family Planning Key Laboratory of Contraceptive Drugs and Devices; Shanghai China
3. Department of Epidemiology; Fielding School of Public Health; University of California; Los Angeles CA USA
4. National Centre for Register-Based Research; Aarhus University; Aarhus Denmark
5. CIRRAU-Centre for Integrated Register-based Research; Aarhus University; Aarhus Denmark