While age-related changes in menstrual cycle length are well-known, it is unclear whether AMH or other ovarian reserve biomarkers have a direct association with cycle length.To determine the association between biomarkers of ovarian reserve and menstrual cycle length.Secondary analysis using data from Time to Conceive (TTC), a prospective time-to-pregnancy cohort study. The age-independent association between cycle length and biomarkers of ovarian reserve was analyzed using linear mixed and marginal models.TTC enrolled women aged 30 to 44 with no history of infertility who were attempting to conceive for <3 months. Serum AMH, FSH, and Inhibin B levels were measured on cycle day 2, 3, or 4. Participants recorded daily menstrual cycle data for ≤ 4 months.Primary outcome was menstrual cycle length; follicular and luteal phase lengths were secondary outcomes.Multivariable analysis included 1880 cycles from 632 women. Compared with AMH levels of 1.6-3.4 ng/mL, women with AMH <1.6 ng/mL had cycles and follicular phases that were 0.98 (95% Confidence Interval (CI): -1.46, -0.50) and 1.58 days shorter (95% CI: -2.53, -0.63), respectively, while women with AMH >8 ng/mL had cycles that were 2.15 days longer (95% CI: 1.46, 2.83), follicular phases that were 2 days longer (95% CI 0.77, 3.24), and luteal phases that were 1.80 days longer (95% CI 0.71, 2.88).Increasing AMH levels are associated with longer menstrual cycles due to both a lengthening of the follicular and the luteal phase independent of age.
Benjamin S Harris, Anne Z Steiner, Anne Marie Jukic