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; Tor Vergata University; Rome Italy
4. Department of Obstetrics and Gynecology; New York University School of Medicine; New York NY USA
5. Department of Obstetrics and Gynecology; Skåne University Hospital Malmö, Lund University; Malmö Sweden