[1] HOSP UNIV PENN, DEPT OBSTET & GYNECOL, 3400 SPRUCE ST, PHILADELPHIA, PA 19104 USA
[2] UNIV PENN, SCH MED, DEPT OBSTET & GYNECOL, PHILADELPHIA, PA 19104 USA
[3] UNIV PENN, SCH MED, DEPT PATHOL & LAB MED, PHILADELPHIA, PA 19104 USA
[4] UNIV PENN, SCH MED, DEPT PHYSIOL, PHILADELPHIA, PA 19104 USA