1. Reference Laboratory for Pre- and Neonatal Screening/Laboratory for Infectious Diseases and Screening; National Institute for Public Health and the Environment; Bilthoven The Netherlands
2. Department of Clinical Genetics; University Medical Center Amsterdam; Amsterdam The Netherlands
3. Department of Obstetrics and Prenatal Medicine; Erasmus MC Rotterdam, Stichting Prenatale Screening; Rotterdam The Netherlands
4. Department of Obstetrics, Prenatal Diagnosis and Therapy; Radboud University Medical Center; Nijmegen The Netherlands
5. Department of Obstetrics; University Medical Center Utrecht; The Netherlands