1. Department of Obstetrics and Gynecology Valme University Hospital Seville Spain
2. Department of Obstetrics and Gynecology, Faculty of Medicine University of Seville Seville Spain
3. Department of Obstetrics and Gynecology Complejo Asistencial Universitario de Gran Canarias Gran Canarias Spain
4. Department of Obstetrics and Gynecology Complejo Asistencial Universitario de Leon (CAULE) León Spain
5. Department of Obstetrics and Gynecology University Hospital Virgen de la Victoria of Malaga Malaga Spain
6. Biostatistics Unit, Department of Preventive Medicine and Public Health University of Seville Seville Spain