Four weeks pregnant with a little blood and then no more may be related to the first sign of abortion, cervical polyps and other reasons, need to be specifically analyzed. 1. Pre-eclampsia: four weeks of pregnancy due to progesterone deficiency, fatigue, external forces and other reasons between the gestational sac and the wall of the uterus stripped, resulting in capillary rupture, a small amount of vaginal bleeding, if the condition does not continue to aggravate, it can be manifested as a small amount of vaginal bleeding after the disappearance. 2. Cervical polyps: If there are cervical polyps, the surface of the polyp rupture sometimes can also be manifested as a small amount of vaginal bleeding. Bleeding in the fourth week of pregnancy may also be ectopic pregnancy, abnormal embryonic development and other reasons, even if it is a small amount of vaginal bleeding, we should go to the hospital in a timely manner to carry out the relevant examinations, do not take the initiative to deal with it, so as to avoid adverse consequences.