Bleeding between periods is called breakthrough bleeding, dysfunctional uterine bleeding, or metrorrhagia. It can happen when you ovulate, or just randomly. It can amount to an occasional spot of blood now and again, or it can be heavy bleeding. But it happens when you don’t expect it. Sometimes, but not always, bleeding between periods is accompanied by heavy periods.
Bleeding between periods, like irregular periods, is quite common in girls just starting their periods and in older women heading toward menopause. They may not ovulate every single month and when they do, they do not produce enough progesterone to stabilize the uterine lining through the second half of the monthly cycle. But if you bleed between periods once you have established a regular cycle and before you are close to menopause, talk to your doctor. Irregular bleeding can be a sign of endometrial (uterine) cancer or some other medical condition.
Is it dangerous to spot a couple of days before your period starts?
Spotting just before your period is quite common and probably nothing to worry about. It probably means that your progesterone levels are dropping before your period, but you should probably mention this to your physician.
Is it dangerous to spot or bleed a little at the time of ovulation’?
This is fairly common; as long as the bleeding is related to the hormonal changes at the time of ovulation, it is nothing more than a nuisance. When a mature egg is released from the ovary during ovulation, your estrogen level peaks and then falls off rapidly, around day 14 of the cycle. At about the same time, production of luteinizing hormone also peaks. Usually the bleeding caused by these hormonal spikes amounts to a bit of spotting that lasts a day or two. Some women simultaneously feel pain on one side of their abdomen (technically known as mittelschmerz, or middle pain). Your doctor may want to rule out other possibilities by using an endometrial biopsy or an ultrasound scan. For some women mittelschmerz can be very uncomfortable. Once you and your doctor have determined that the bleeding results from normal hormonal changes, you can decide to live with the bleeding or you can try birth control pills, which solve the problem by preventing ovulation.
Among the medical conditions that can cause bleeding between periods are endometriosis, adenomyosis, fibroids, polyps, pelvic inflammatory disease, a tubal or ectopic pregnancy, or an incomplete miscarriage (all of these problems are discussed elsewhere in this site). Another possibility is cancer, particularly cancer of the endometrium (uterine cancer), which is relatively rare among women in general — about six times less common than breast cancer — and extremely rare in young women.