Further study of d-norgestrel for fertility control.

In a continuing oral contraceptive study of d-norgestrel, the 1,0-mg dose--the dose previously found to give the best cycle control--was administered cyclically on a "21-7 day" schedule to 284 women during 2650 cycles. None of the women conceived, and cycle control, though often altered, was generally acceptable. Side effects were minimal, and laboratory determinations performed prior to and during the administration of this agent revealed no clinically significant changes.