Prevention is related to the cause. For instance, practicing safer sex can help avoid bleeding due to sexually transmitted diseases. Regular Pap smears can help prevent cancer of the cervix. A woman who is on oral contraceptives should take them as prescribed. Aspirin should be avoided, if possible, because it may cause bleeding. Many cases cannot be prevented, but can be treated.
Too much blood loss can result in anemia, or a low blood count. Other long-term effects are primarily related to the underlying cause. For instance, pelvic inflammatory disease may result in infertility, or the inability to have children. Trauma to the vagina may heal and cause no long-term effects. Cancer may result in death.
Bleeding between periods is not contagious and usually poses no risks to others. If the cause of bleeding is an infection, the infection may be contagious and passed on to sexual partners.