Mikel Gorostidi1, Ruben Ruiz2. 1. Department of Obstetrics and Gynecology, Hospital Universitario Donostia, Guipuzkoa 20014, Spain. Electronic address: mgorostidi@sego.es. 2. Department of Obstetrics and Gynecology, Hospital Universitario Donostia, Guipuzkoa 20014, Spain.