A common cause of bleeding in the first trimester is Cervical Changes in Pregnancy. This is bleeding from the sensitive cells of the cervix coming in contact with the vaginal walls. Bleeding can occur after prolong walking or from sexual intercourse. This type of bleeding is not a cause for concern. Other causes of bleeding in the first trimester are: Implantation bleeding : where bleeding occur from the pregnancy trying to sit itself in the womb. Infection : like chlamydia, trichomonas or severe candidiasis. Miscarriage : by far is the most concern cause. When bleeding is severe and with cramps, half of the women may end up with a miscarriage. In the majority of these unfortunate cases, the bleeding is a result of a failing pregnancy rather than the cause of it. Although there is no treatment to prevent a miscarriage, Progesterone support is usually given in the hope that it will help a precarious pregnancy continue to develop properly. Ectopic Pregnancy : is a condition where the pregnancy is outside the womb, usually in the fallopian tube. This form of bleeding is usually associated with localized pelvic pain. It is important to confirm the location of the pregnancy as ectopic pregnancy can be dangerous to your life. Bleeding in the late pregnancy can be because of : Infection : similar to that in first trimester when bleeding is from the cervix. Marginal Vessel Bleed : where small blood vessels around the placenta bleeds. The bleeding usually stops spontaneously and will not harm the pregnancy. Placenta Previa : where the placenta sits low in the womb, partially covering the outlet of the womb. It occurs in 0.5% of pregnancies and requires immediate medical attention. If bleeding is associated with pain, you should go to the hospital because the possible causes include Premature Labour and other conditions that your doctor will check for.