A longitudinal study questions the accepted relationship between antral follicle count (AFC) and age

Abstract

OBJECTIVE: Ovarian aging plays a key role in success with fertility treatment. It is accepted that the rate of AFC decline accelerates with age. To date, most of the data regarding this relationship are cross-sectional. We sought to determine how AFC declines within individuals in an infertile population by performing a longitudinal study. DESIGN: Retrospective longitudinal. MATERIALS AND METHODS: 1500 charts, from patients with infertility (2000-2008), were reviewed. 348 patients (25-54yo) with repeated longitudinal AFC measurement of at least 1 year apart (1-7 yrs), were analyzed. Mixed effect repeated measures linear regression was used to estimate the ave decline in AFC/year and to allow individual specific initial AFC and rates of decline. Results were adjusted for OCP/lupron use. Random effect predictions were performed to estimate the rate of AFC decline for each individual. RESULTS: There was a significant decline of 1.3 AFC/yr (95% CI -1.73, -0.87). No evidence of accelerating decline with age was found and, in fact, there was a non-statistically significant trend towards decelerating decline with age. Moreover, the rate of decline depended strongly on the initial AFC: higher initial AFC was associated with faster decline (r= -0.91). The magnitude of this association and the relative lack of association with initial age are displayed in Table 1.Tabled 1Changes in AFC/year from Initial AgeInitial AFC25-35yo36-40yo41-45yoAFC > 20−2.50−2.31−2.00AFC < 10−1.10−1.25−1.28 Open table in a new tab CONCLUSIONS: This is the largest longitudinal study, to date, evaluating changes in AFC over time in a statistically rigorous manner. Our data show the rate of AFC decline does not increase with age. An additional novel finding is the strong impact on the rate of decline of the initial AFC with a decreased rate of decline in women with lower AFC. These data bring into question the common dogma that follicle loss accelerates, in the late 30s, or when a fixed follicle number (25K) is reached.