Ovarian follicular development in oral contraceptive cycles

The cyclic changes in serum hormone concentrations, ovarian follicular development, uterine size, and endometrial appearance have been observed in 58 spontaneous ovulatory cycles and compared with 22 initial cycles of oral contraceptive (OC) therapy. A far greater inhibitory effect on the ovary was achieved by starting contraception on day 1 of the cycle rather than on day 5. The relevance of these findings with regard to OC failures is discussed.