A small amount of fresh blood at 5 weeks of pregnancy may be caused by physiological reasons, cervical polyps, pre-miscarriage, ectopic pregnancy and other reasons. 1. Physiological reasons: after pregnancy, some pregnant women will be in the fertilization of the egg during the vaginal flow of a small amount of blood, usually lasts for 3-4 days after the disappearance of most of their own, this is a normal physiological phenomenon, do not need special treatment. 2. Cervical polyps: also cause a small amount of blood in the vagina during early pregnancy, not accompanied by abdominal pain, may recur, through gynecological examination, ultrasonography and so on to assist in the diagnosis. 3. Pre-eclampsia: mainly manifested by a small amount of vaginal bleeding, which may be fresh blood or brown, accompanied by paroxysmal pain in the lower abdomen. After ultrasound examination is performed to clarify the intrauterine pregnancy, combined with progesterone and blood HCG (human chorionic gonadotropin) test, etc., the diagnosis can be assisted. 4. Ectopic pregnancy: It can also cause irregular vaginal bleeding, which may be fresh blood, accompanied by vague pain in one side of the lower abdomen, which can be diagnosed by ultrasonography and blood HCG test. When a small amount of fresh blood appears in the 5th week of pregnancy, it is necessary to go to the hospital promptly in order to identify the cause and deal with it actively.