Harris BS, et al. - Using linear mixed and marginal models, researchers intended to determine if there is an association between biomarkers of ovarian reserve and menstrual cycle length. TTC enrolled women between the ages of 30 and 44 who had no history of infertility and were attempting to conceive for < 3 months. On cycle day 2, 3, or 4, serum AMH, FSH, and Inhibin B levels were measured. For ≤ 4 months, participants recorded daily menstrual cycle data. A total of 1,880 cycles from 632 women were included in the multivariable analysis. Increased AMH levels are linked to longer menstrual cycles due to a lengthening of both the follicular and luteal phases, which occurs regardless of age.