1. Department of Epidemiology; University of Groningen; University Medical Centre Groningen; Groningen the Netherlands
2. Department of Obstetrics & Gynaecology; University of Groningen; University Medical Centre Groningen; Groningen the Netherlands
3. Department of Obstetrics & Gynaecology; Bronovo Hospital; Den Haag the Netherlands
4. Department of Obstetrics & Gynaecology; Leiden University Medical Centre; Leiden the Netherlands
5. Department of Clinical Epidemiology and Biostatistics; Academic Medical Centre; Amsterdam the Netherlands
6. Department of Obstetrics & Gynaecology; Onze Lieve Vrouwe Gasthuis; Amsterdam the Netherlands
7. The Robinson Institute; School of Paediatrics and Reproductive Health; University of Adelaide; North Adelaide SA Australia