1. Department of Obstetrics and Gynecology, Fetal Medicine Unit; University Medical Centre; Groningen The Netherlands
2. Department of Genetics, University Medical Centre Groningen; University of Groningen; Groningen The Netherlands
3. Department of Obstetrics and Gynecology, Fetal Medicine Unit; Academic Medical Centre; Amsterdam The Netherlands
4. Prenatal Screening Foundation Northeast Netherlands; University Medical Centre; Groningen The Netherlands