1. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology , University of Florida College of Medicine , Gainesville, FL , USA
2. Department of Obstetrics and Gynecology , University of Illinois College of Medicine , Chicago, IL , USA
3. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology , University of Florida College of Medicine , PO Box 100294 , Gainesville, FL 32610-0294 , USA , Tel.: (352) 273-7562, Fax: (352) 294-5094