[1] Univ Iowa, Med Scientist Training Program, Carver Coll Med, Iowa City, IA USA
[2] Univ Iowa, Coll Publ Hlth, Dept Epidemiol, Iowa City, IA USA
[3] Univ Michigan, Dept Obstet & Gynecol, Ann Arbor, MI 48109 USA
[4] Univ Iowa, Carver Coll Med, Med Training Program, Iowa City, IA USA
[5] Univ Iowa, Tippie Coll Business, Dept Business, Iowa City, IA USA
[6] Duke Univ, Dept Surg, Durham, NC USA
[7] Univ Iowa Hosp & Clin, Dept Surg, SE 427 GH,200 Hawkins Dr, Iowa City, IA 52242 USA