1. Department of Obstetrics and Gynecology; VU University Medical Center; Amsterdam Netherlands
2. Medical library; Vrije Universiteit; Amsterdam Netherlands
3. Department of Epidemiology and Biostatistics; VU University Medical Center; Amsterdam Netherlands
4. Department of Pediatric Cardiology; Emma Children's Hospital; Academic Medical Center; Amsterdam Netherlands
5. Department of Pediatric Cardiology; Leiden University Medical Center; Leiden Netherlands
6. Department of Obstetrics and Gynecology; Leiden University Medical Center; Leiden Netherlands