Bleeding has many possible causes. In early pregnancy, light spotting can sometimes occur around the time implantation would happen or be harmless, but it can also signal miscarriage or an ectopic pregnancy. In later pregnancy, bleeding may relate to the placenta and can be more serious.
Because the cause cannot be known without assessment, any bleeding should be reported to your maternity team. Note the amount, colour, and any pain so you can describe it.
Seek urgent or emergency care if bleeding is heavy, comes with severe or one-sided abdominal pain, shoulder-tip pain, dizziness or fainting, or occurs in later pregnancy. These can indicate an emergency such as ectopic pregnancy or placental problems and need immediate attention. When in doubt, call your maternity unit or local emergency number.