According to the American Society for Reproductive Medicine, amenorrhea that is not caused by pregnancy, breastfeeding, or menopause occurs in a small percentage (less than 5%) of women during their lifetime.
Master-Hunter, T., & Heiman, D. L. (2006). Amenorrhea: Evaluation and treatment. American Family Physician, 73, 1374–1382. Retrieved May 31, 2016, from http://www.aafp.org/afp/2006/0415/p1374.html