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