What causes late periods?

Pregnancy and . . .: Pregnancy is the biggest concern/condition in a female of childbearing age who has missed her period. If she's not pregnant, then anovulatory cycles are a common cause of irregular periods in young women. Thyroid disease can also make your menses irregular. Female athlete triad includes amenorrhea in addition to eating disorder & osteoporosis.

Late periods: Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems (i.e. PCOS). #1 reason is pregnancy.