Antral follicle counts by transvaginal ultrasonography are related to age in women with proven natural fertility

Objective: To investigate the relation between reproductive age and ultraso und (US)-based follicle counts and the reproducibility of follicle counts i n regularly cycling women with proven fertility. Design: Prospective observational study. Setting: Tertiary fertility center. Patient(s): Healthy female volunteers with proven fertility, recruited by a dvertisement in local newspapers. Intervention(s): The number of antral follicles sized 2-10 mm and ovarian v olume were estimated by transvaginal US in the early follicular phase of th e menstrual cycle in 162 women. A subgroup of 81 women underwent transvagin al US at several times in three subsequent cycles. Main Outcome Measure(s): Antral follicle count and total ovarian volume. Result(s): Women aged 25-46 years (n = 162) were studied. The relation of a ge with the US indices was computed after natural log transformation. Antra l follicle count showed the dearest correlation with age (R = -0.67). A bip hasic linear model gave the best fit to the data. Before the age of 37 year s, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. Conclusion(s): The number of small antral follicles in both ovaries as meas ured by US is clearly related to reproductive age and could well reflect th e size of the remaining primordial follicle pool. (Fertil Steril(R) 1999; 7 2:845-51. (C) 1999 by American Society for Reproductive Medicine.)