The causes of recurrent vaginal bleeding during birth control include improper medication, embryonic abnormalities, placental factors, infection, ectopic pregnancy, etc. 1. Improper medication: If a woman takes the wrong kind of birth control medication, or takes less or omits to take birth control medication, the effect of birth control will be affected and recurrent vaginal bleeding will occur, so it is recommended that medication should be used under the guidance of a doctor to avoid blind medication. 2. If the embryo is of poor quality, even if the pregnancy is preserved, it cannot change the result of miscarriage, so there will be recurrent vaginal bleeding, and the pregnancy should be terminated according to the situation. The pregnancy can be prolonged by bed rest, close monitoring of fetal development, and termination of pregnancy at the appropriate time after the fetus is full term; 4, infection: bacterial infection caused by improper care in daily life may lead to bleeding, which requires the application of drugs for anti-inflammatory and uterine contraction inhibition treatment as prescribed by the doctor to reduce the occurrence of bleeding; 5, ectopic pregnancy: ectopic pregnancy, with the gradual growth and development of the fetus, can also cause vaginal bleeding after the treatment of fetal preservation. In this case, ultrasound examination should be improved to terminate the pregnancy after clear diagnosis.