1. Department of Obstetrics and Gynecology; VU University Medical Center; Amsterdam The Netherlands
2. Department of Anatomy and Embryology; Leiden University Medical Center; Leiden The Netherlands
3. Department of Obstetrics and Gynecology; Radboud University Medical Center; Nijmegen The Netherlands
4. Center for Prenatal Diagnosis and Human Genetics; Berlin Germany
5. Department of Cardiology; Leiden University Medical Center; Leiden The Netherlands
6. Department of Obstetrics and Gynecology; Leiden University Medical Center; Leiden The Netherlands