Effect of pregnancy/gestational age, menopause/aging, parity, and prolapse on the “stiffness” of the reproductive organs and tissues. In the cited studies (numbers in square brackets), different mechanical quantities are used as stiffness measures. Note that U stands for uterus, C for cervix, V for vagina, USL for uterosacral ligament, CL for cardinal ligament, RL for round ligament, and BL for broad ligament.