Growth patterns of nondominant ovarian follicles during the normal menstrual cycle.

Transvaginal ultrasound examinations were performed in seven normally cycling women to characterize growth of nondominant follicles in both ovaries. Mean follicle number showed little variation throughout the menstrual cycle with no differences between dominant and nondominant ovaries. Up to 11 follicles (greater than or equal to 2 mm) were observed in any one ovary. From observations of the first appearance of the dominant follicle (mean size 9.9 +/- 3.0 [SD] mm), selection was assumed to take place on cycle day 6.3 +/- 2.3. The diameter of nondominant follicles always remained less than 11 mm. Growth of small follicles was established in both dominant and nondominant ovaries up to the time of selection. The late follicular and luteal phases were characterized by a decrease in mean growth slopes of nondominant follicles in the dominant ovary only. These observations may provide in vivo evidence for the concept of intraovarian paracrine mechanisms and may have implications for the sonographic diagnosis of anovulation and monitoring of ovulation induction.