Dominant follicles
A dominant ovarian follicle refers to the follicle that enlarges to release an ovum during a menstural cycle. Usually approximately 10 Graafian follicles begin to mature where one becomes a dominant follicle and the rest become atretic ovarian follicles. After release of the ovum the remainder of the dominant follicle turns into a corpus luteum and finally into a scarred corpus albicans. On occasion there can be two or more dominant follicles.
Generally the accepted ultrasound size cut off for a dominant follicle is between 1-2 cm (see the 1-2-3 rule).