Some patients may experience vaginal bleeding after taking birth control drugs, probably because birth control requires a process. Although there is bleeding at present, the bleeding will decrease until it disappears as the fetus gradually and steadily develops. If the bleeding still persists or the amount of blood is high, we need to pay attention to it and carry out further fetal preservation treatment after identifying the cause of bleeding. Common reasons include: 1. Improper medication: if the medication is used improperly or in insufficient dosage, it may not be able to play a better fetal preservation effect, thus leading to bleeding; 2. Inevitable miscarriage: if the bleeding is caused by abnormal embryonic development, vaginal bleeding may occur even if the fetal preservation medication is applied 3, ectopic pregnancy: also known as ectopic pregnancy, because the pregnant egg is laid outside the uterine cavity, the application of birth control pills has no effect at this time, and as the fetus grows, it will also lead to bleeding; 4, cervical disease: if there are superfluous organisms in the cervix, vaginal bleeding will also occur. If the bleeding occurs after the application of birth control pills, it is necessary to review the ultrasound and check the blood chorionic gonadotropin and progesterone values to determine whether the embryo is alive. If the embryo is developing well, the treatment can be continued by changing the birth control medication. If the embryo has died, there is no need to continue the birth control and the uterus should be cleared to avoid the fetal sac and fetal appendages staying in the uterine cavity for a long time and causing uterine infection.