1. Department of Obstetrics and Gynecology; Stavanger University Hospital; Stavanger Norway
2. National Center for Fetal Medicine; Trondheim University Hospital (St Olavs Hospital); Trondheim Norway
3. Fetal Medicine Department, Rosie Maternity Hospital, Addenbrooke's Hospital; Cambridge University Hospitals NHS Foundation Trust; Cambridge UK
4. Department of Obstetrics and Gynaecology, Clinical Sciences; Lund University; Lund Sweden
5. Department of Laboratory Medicine, Children's and Women's Health; Norwegian University of Science and Technology; Trondheim Norway
6. Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital; Imperial College Healthcare NHS Trust; London UK