A small amount of bleeding 20 days after miscarriage may be caused by a small amount of residue in the uterine cavity after miscarriage, and a small amount of vaginal bleeding due to normal menstruation 20 days after miscarriage cannot be excluded. At this time, an ultrasound examination is needed to find out whether there is residue in the uterine cavity or the thickness of the endometrium in the uterine cavity to indicate the onset of menstruation. In general, there is no normal menstruation after 20 days of miscarriage, and it may cause residues in the uterine cavity, so it is necessary to perform hysteroscopy, if necessary, to find out if there are residues in the uterine cavity and to remove them under hysteroscopy. If the possibility of menstruation is excluded, the residue can be temporarily observed.