Spotting, or breakthrough bleeding, in between periods is common, and many women experience it at some point in their lives, according to WebMD. Some light bleeding in between periods is usually not serious, though unusual amounts of bleeding at an atypical time during the menstrual cycle can indicate a medical problem, particularly if a woman might be pregnant. Any significant bleeding during pregnancy can signal a serious problem.
About 10 percent of women experience spotting during ovulation during the middle of their cycles, explains
Everyday Health. Stress can cause variations in hormones, leading to slight bleeding at other times. Slight irregular bleeding is rarely anything serious.
Spotting can be the first sign of pregnancy, as the embryo attaches to the uterine wall, according to Everyday Health. Heavy bleeding or cramping during pregnancy, particularly in the first 12 weeks, can announce a miscarriage or ectopic pregnancy. During perimenopause, indiscriminant bleeding can be common as the menstrual cycle becomes less regular. After menopause, any bleeding from the vagina can result from a serious medical issue, such as cancer. WebMD summarizes that other medical causes of bleeding in women of childbearing years include birth control pills, polycystic ovary syndrome, uterine fibroids, sexually transmitted diseases, pelvic inflammatory disease and other diseases, such as diabetes, cancer or hyperthyroidism.