1. Department of Obstetrics and Gynaecology, Reproduction and Development Amsterdam UMC Vrije Universiteit Amsterdam Amsterdam The Netherlands
2. Department of Epidemiology and Biostatistics Amsterdam UMC Vrije Universiteit Amsterdam Amsterdam The Netherlands
3. Department of Obstetrics and Gynaecology, Reproduction and Development Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
4. Department of Medical Library Amsterdam UMC Vrije Universiteit Amsterdam Amsterdam The Netherlands
5. Department of Obstetrics and Gynaecology Monash University Clayton Vic. Australia
6. Department of Clinical Epidemiology, Biostatistics and Bioinformatics Amsterdam UMC University of Amsterdam Amsterdam The Netherlands