It can be totally normal to spot all throughout a pregnancy. As long as the spotting does not turn into full-fledged bleeding and is accompanied by pain, or the blood is not bright red, I would say you have nothing to worry about.

It's most normal at the beginning of your pregnancy (implantation bleeding). Later it can be a sign of infection, miscarriage, ectopic pregnancies, or placental problems. It can also be perfectly normal, but just to be safe you should talk to your doctor.