1. Faculty of Medicine, Universidad Nacional de Colombia; Department of Obstetrics & Gynecology and Clinical Research Institute; Carrera 30 No 45-03 Bogota Colombia
2. Faculty of Medicine, Universidad Nacional de Colombia; Department of Obstetrics & Gynecology; Cra 30 # 45-03 Bogota Colombia
3. Faculty of Medicine, Universidad Nacional de Colombia; Clinical Research Institute; Bogota Colombia
4. University of Auckland; Department of Obstetrics and Gynaecology; Private Bag 92019 Auckland New Zealand 1142