Pregnancy related bleeding can be a reason for abnormal bleeding, even if you have not missed a period. Many women believe that if they have not missed a period then it is not possible to be pregnant; this is not true. It is possible to have had bleeding as results of complications during the pregnancy. That is why it is important to have a pregnancy test whenever you have any abnormal bleeding. Sometimes it is necessary to measure the pregnancy hormone BHCG to exclude ectopic pregnancy or abnormal growth of the placenta e.g. Hydatidiform mole.