1. Department of Obstetrics and Gynecology; Catholic University of the Sacred Heart; Rome Italy
2. Gynecology and Early Pregnancy Ultrasound Unit, Department of Obstetrics and Gynecology; University of Bologna; Bologna Italy
3. Department of Obstetrics and Gynecology; Karolinska University Hospital; Stockholm Sweden
4. Department of Obstetrics and Gynecology; New York University School of Medicine; New York NY USA
5. Department of Gynecology; Policlinico Abano Terme; Abano Terme Italy
6. Department of Obstetrics and Gynecology; Università degli Studi di Roma Tor Vergata; Rome Italy
7. Department of Radiology and Obstetrics and Gynecology; Brigham and Women's Hospital, Harvard Medical School; Boston MA USA
8. Department of Obstetrics and Gynecology; Skåne University Hospital Malmö, Lund University; Malmö Sweden