Potential role of physical labor and cultural views of menstruation in high incidence of pelvic organ prolapse in Nepalese women: a comparative study across the menstrual cycle oleh Yvonne Biswokarma, Karen Brandon, Everett Lohman, Ryan Stafford, Noha Daher, Jerold Petrofsky, Uma Thapa, Lee Berk, Robert Hitchcock, Paul W. Hodges