[1] Washington Univ, Sch Med, Dept Obstet & Gynecol, Div Family Planning, St Louis, MO 63110 USA
[2] Washington Univ, Sch Med, Dept Obstet & Gynecol, St Louis, MO 63110 USA
[3] Washington Univ, Sch Med, Dept Surg, Sect Acute & Crit Care Surg,Div Gen Surg, St Louis, MO 63110 USA
[4] Washington Univ, Sch Med, Dept Internal Med, Cardiovasc Div,Ctr Hlth Econ & Policy,Inst Publ H, St Louis, MO 63110 USA