1. Unit of Obstetrics and Gynecology, Department of Biomedical and Clinical Sciences, ASST Fatebenefratelli Sacco, Hospital “L. Sacco,” University of Milan, Italy
2. Centre for Fetal Research Giorgio Pardi, University of Milan, Italy
3. Statistical and Biometry Unit, Department of Biomedical and Clinical Sciences, Hospital “L. Sacco,” University of Milan, Milan, Italy