1. Department of Obstetrics and Gynaecology, Viladecans Hospital, Avenue Gavà 38 Viladecans, 08840 Barcelona, Spain
2. Department of Obstetrics and Gynaecology, Hospital of the Hdy cross and Saint Paul, Mas Casanovas 90, 08025 Barcelona, Spain
3. Department of Epidemiology, Hospital of the Hdy cross and Saint Paul, Mas Casanovas 90, 08025 Barcelona, Spain