A small amount of blood 40 days after delivery needs to be treated according to its cause, such as physiological phenomenon, incomplete uterine regeneration, placenta and its appendages residue, etc. After clear diagnosis, general treatment and medication will be chosen. 1. Physiological phenomenon: a small amount of blood 40 days after delivery may be a menstrual period. The recovery time of menstruation after delivery varies greatly for different women, so menstruation can occur 40 days after delivery and no special treatment is needed. 2. Incomplete uterine regeneration: a small amount of blood 40 days after delivery may also be caused by incomplete uterine regeneration. It is recommended that women actively promote breastfeeding, through the baby’s sucking on the nipple, to promote the release of uterotonin, and can choose to uterotonin treatment if necessary. 3. Placenta and its appendages: the presence of placenta and its appendages in the uterus can lead to poor uterine contraction, and may even cause infection of the placental attachment surface, resulting in bleeding, it is recommended that the uterus can be removed. There are many reasons why there is a small amount of blood 40 days after delivery, if bleeding still occurs, it is recommended to consult a doctor to find out the cause and take treatment under the doctor’s guidance.