Period blood that is dark in color is very common at the beginning and especially at the end of your period, and is not always associated with a health condition.
However, small amounts of dark period blood can also be a sign of hormonal changes, menopause, sexually transmitted infections (STIs), endometriosis, or injury to the cervix, which can affect menstrual flow and may explain why the blood appears darker.
This type of bleeding is rarely considered a sign of pregnancy. In early pregnancy, some women may experience light implantation bleeding, but it is usually pink in color. It is uncommon for pregnancy-related bleeding to be dark brown.
If you have dark brown bleeding that lasts longer than seven days, is heavy, or is accompanied by pelvic pain, it is important to consult a gynecologist.