[1] JOHNS HOPKINS UNIV, SCH MED, DEPT MED, DIV CLIN PHARMACOL, BALTIMORE, MD 21205 USA
[2] JOHNS HOPKINS UNIV, SCH MED, DEPT OBSTET & GYNECOL, BALTIMORE, MD 21205 USA
[3] NICHHD, CONTRACEPT DEV BRANCH, ROCKVILLE, MD USA
[4] US FDA, CTR DRUG EVALUAT & RES, ROCKVILLE, MD 20857 USA