1. Department of Obstetrics and Gynaecology; VU University Medical Centre; Amsterdam the Netherlands
2. Robinson Research Institute; University of Adelaide; Women's and Children's Hospital; North Adelaide SA Australia
3. Department of Epidemiology and Biostatistics; VU University Medical Centre; Amsterdam the Netherlands
4. Department of Obstetrics and Gynaecology; Onze Lieve Vrouwe Gasthuis; Amsterdam the Netherlands