[1] EASTERN VIRGINIA MED SCH,DEPT PHYSIOL,NORFOLK,VA 23501
[2] EASTERN VIRGINIA MED SCH,DEPT OBSTET & GYNECOL,NORFOLK,VA 23501
[3] UNIV MARYLAND,SCH MED,CTR STUDIES REPROD,DEPT OBSTET GYNECOL,BALTIMORE,MD 21201
[4] UNIV MARYLAND,SCH MED,CTR STUDIES REPROD,DEPT PHYSIOL,BALTIMORE,MD 21201