1. Department of Obstetrics and Gynecology , Fondazione Policlinico Tor Vergata, University of Rome Tor Vergata , Rome , Italy
2. Departement of Epidemiology , Universita di Ferrara , Ferrara , Italy
3. Department of Maternal and Child Health and Urological Sciences , Sapienza University of Rome , Rome , Italy
4. Centre for Fetal Care and High-risk Pregnancy, Department of Obstetrics and Gynecology , University of Chieti , Chiety , Italy