Prediction of ovarian cycle outcome by follicular characteristics, stage 1.

Both dominant and subdominant follicles have been identified and individually monitored over the follicular phases of 54 natural cycles in 36 women. Population dynamics of all antral follicles, visible by ultrasonography, in the ovary over the entire cycle have also been characterized for the first time. This has been accomplished by developing a new system of mapping and monitoring follicles, including a three-dimensional computer imaging model and correlation program. The different dominant follicle types were characterized by their ultrasonographic properties. Ovulatory follicles were rounded in shape and mid-range echogenic, with a smooth antral edge by late follicular phase. Luteinized unruptured follicles were round, had low echogenicity and a very smooth antral edge. Atretic follicles were irregular in shape and antral edge and had mid-range echogenicity. A further important finding was that follicle success appears to be related to timing of growth and to the subdominant follicle population present in the ovary. An analysis of follicle population dynamics in ovulatory cycles showed a drastic decrease in number at the end of the luteal phase, followed by a sharp increase at the beginning of the follicular phase. This study has demonstrated that characteristics of individual follicles and population dynamics of both dominant and subdominant follicles are strongly associated with cycle outcome. These findings will contribute towards a predictive model of dominant follicle status and cycle outcome. A new hypothesis of follicle competition has also been proposed.