CONTEXT: The interindividual variation in the age-related decline of ovarian follicles is wide. Hence, it is important to identify reliable, sensitive, and specific markers to assess the ovarian reserve of the individual woman.

OBJECTIVE: The aim of this study was to characterize the relation between age and ovarian reserve parameters in a population of healthy women with regular menstrual cycle.

DESIGN AND SETTING: We conducted a prospective, population-based, cross-sectional study.

PARTICIPANTS: A total of 366 health care workers aged 21-41 years employed at a University Hospital were included. Interventions: There were no interventions.

MAIN OUTCOME MEASURES: Serum anti-Müllerian hormone (AMH) concentration, antral follicle count (AFC), antral follicle size categories (small: 2-4 mm; intermediate: 5-7 mm; and large: 8-10 mm), and ovarian volume were measured.

RESULTS: Serum AMH level declined by 5.6% per year (95% confidence interval 3.7-7.4%, P < .001), AFC (2-10 mm) declined by 4.4% per year (3.2-5.7%, P < .001), and ovarian volume declined by 1.1% per year (0.2-2.0, P = .002), respectively. The mean proportion of small follicles decreased with age (P = .04), the proportion of intermediate follicles displayed no significant change with age (P = .58), and the mean proportion of large follicles increased with age (P < .001). The prevalence of large follicles increased with decreasing serum AMH concentration [odds ratio 1.04 per 1 pmol/L (1.02-1.06), P < .001, area under the curve 0.66], and with decreasing total AFC [odds ratio 1.04 per follicle (1.02-1.05), P < .001, area under the curve 0.62].

CONCLUSION: Chronological age was inversely related to serum AMH concentration, total AFC, and ovarian volume. Subclasses of AFC sized 2-4 and 5-7 mm decreased with increasing age, whereas AFC sized 8-10 mm increased with increasing age. Within AFC, a shift toward larger follicles with increasing age was observed. The occurrence of large follicles was more strongly related to biological age in terms of AMH and AFC than chronological age.