The uterus should not be excited in the early stages of pregnancy, especially in the first trimester, so as to avoid the chances of bleeding, which can lead to the occurrence of preterm miscarriage. Bleeding after masturbation in the first trimester of pregnancy is due to the excitation of the uterine lining, which causes it to shed, and thus blood is discharged from the vagina. In this case, it is recommended to go to the hospital for an ultrasound examination, and also for progesterone, including blood HCG tests, according to the situation need to take oral medication to protect the fetus. If the bleeding increases persistently, it can be changed to intramuscular progesterone for the purpose of fetal preservation. Bleeding will be present for a period of time, which may be seven or ten days, and it is important to adhere to the birth control. As to when to stop taking the medicine, it depends on the bleeding situation, including the results of laboratory tests. In the future, you must pay attention to personal hygiene and prohibit coitus in the first three months to avoid miscarriage.