The most common cause of pain or bleeding with intercourse is infection of the cervix (cervicitis) that occurs with a vaginal infection, such as chlamydia or pelvic inflammatory disease (PID). This is usually accompanied by other symptoms of infection, such as vaginal discharge and irritation, with some redness or soreness. Call your doctor if sex causes pain and you have an abnormal vaginal discharge.
Although cervical cancer is very rare in women who have regular Pap test screening, bleeding with intercourse is the most common symptom.
Any bleeding after having sex that is not part of your regular menstrual period should be evaluated by your doctor.
WebMD Medical Reference from Healthwise