1. Department of Obstetrics and Gynecology, Ultrasound and Fetal Medicine Unit, University Hospital of Canary Islands, Ctra. Ofra, s/n, Santa Cruz de Tenerife, 38320 San Cristóbal de La Laguna, Spain
2. Department of Obstetrics and Gynecology, School of Medicine, University Hospital Policlinico of Bari and University of Bari “Aldo Moro”, Piazza Giulio Cesare 11, 70124 Bari, Italy
3. Department of Obstetrics and Gynecology, University Hospital Puerta de Hierro, Calle Manuel de Falla, 1 Majadahonda, 28222 Madrid, Spain