1. School of Medicine and Dentistry; University of Aberdeen; Aberdeen UK
2. Obstetrics and gynaecology; Division of Applied Health Sciences; School of Medicine and Dentistry; University of Aberdeen; Aberdeen UK
3. Medical Statistics Team; Division of Applied Health Sciences; University of Aberdeen; Foresterhill Aberdeen UK
4. Epidemiology Group; Division of Applied Health Sciences; School of Medicine and Dentistry; University of Aberdeen; Aberdeen UK