How common is it to skip a period?

Possible causes: Reasons for missed /late periods: low body weight, obesity, marked weight gain or loss, over-exercise such as in endurance athletes, breast-feeding, stress, illness, eating disorders (bulimia or anorexia), travel, hormone irregularities, drug use, medications (i.e., birth control) or med problem(polycystic ovary syndrome or asherman’s syndrome. #1 reason for missed period is pregnancy.