1. Center for Clinical Transfusion Research Sanquin Research Leiden the Netherlands
2. Department of Obstetrics Leiden University Medical Center Leiden the Netherlands
3. Department of Clinical Epidemiology Leiden University Medical Center Leiden the Netherlands
4. Department of Hematology Erasmus MC University Medical Center Rotterdam Rotterdam the Netherlands
5. Department of Obstetrics Erasmus MC University Medical Center Rotterdam Rotterdam the Netherlands
6. Division of Thrombosis and Hemostasis Department of Internal Medicine Leiden University Medical Center Leiden the Netherlands
7. Division Woman and Baby Department of Obstetrics, Birth Center Wilhelmina Children Hospital University Medical Center Utrecht Utrecht the Netherlands
8. Faculty of Science VU University Medical Center Athena Institute Amsterdam the Netherlands
9. National Perinatal Epidemiology Unit University of Oxford Oxford UK