Dick Oepkes1, Ann Tabor2, Yuval Yaron3. 1. Department of Obstetrics, Leiden University Medical Center, Albinusdreef 2, Leiden, 2333AA The Netherlands. Electronic address: d.oepkes@lumc.nl. 2. Department of Obstetrics, The Juliane Marie Centre, Rigshospitalet, Copenhagen University Hospital, DK-2100 Copenhagen, Denmark. 3. Tel Aviv Sourasky Medical Center, Tel Aviv 64239, Israel.