1. Department of Obstetrics and Gynecology, Hospital Virgen de la Concha, 49022 Zamora, Spain
2. Department of Obstetrics and Gynecology, Hospital Universitario de Salamanca, University of Salamanca, Institute for Biomedical Research of Salamanca (IBSAL), 37007 Salamanca, Spain
3. Preventive Medicine and Public Health Area, University of Salamanca, Institute for Biomedical Research of Salamanca (IBSAL), Tropical Disease Research Centre of the University of Salamanca (CIETUS), 37008 Salamanca, Spain