1. Department of Obstetrics and Gynecology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
2. School of Psychology, University of Ottawa, Ottawa, Ontario, Canada
3. Department of Clinical Psychology and Experimental Psychopathology, University of Groningen, Groningen, The Netherlands
4. Department of Surgery, Anorectal Physiology Laboratory, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands