Part of “CHAPTER 95 – THE NORMAL MENSTRUAL CYCLE AND THE CONTROL OF OVULATION“

In the absence of pharmacologic intervention, multiple ovulation is extremely atypical in women. The primordial follicle must slowly develop and grow for many months before it becomes a 5- to 8-mm antral follicle at the beginning of the cycle during which it will potentially ovulate.93 Normally, many follicles reach this stage at the first half of each follicular phase (see Chap. 94). The process that follows has been termed recruitment94,94a (Fig. 95-13). Several morphologically identical follicles may be observed within the ovary before cycle days 5 to 7. The destruction of any one of these follicles does not delay ovulation. In contrast, after about cycle day 7, the multipotentiality of these follicles is lost. Henceforth, only one follicle is capable of progressing to ovulation in the current cycle. This one follicle, destined to ovulate and form the corpus luteum, is known as the dominant follicle. Destruction of the dominant follicle, such as by selective cautery, delays ovulation by approximately the number of days that have passed from cycle onset to follicle destruction.95 The point in time in the cycle at which all of the recruited follicles become qualitatively unequal in potential is the time of selection. That the process of selection is predetermined by some intrinsic aspect of a particular follicle seems unlikely. However, once acquired, dominance cannot be transferred. On selection of the single dominant follicle, all other follicles become destined for atresia.