Bleeding for 18 days of blastocyst transfer may be caused by preeclampsia, ectopic pregnancy and gynecological diseases. 1. Pre-eclampsia: Blastocyst transfer is artificial insemination, the body is not able to secrete progesterone accordingly to promote the growth and development of the fetus, the body’s progesterone value is low, and does not support the pregnancy may cause pre-eclampsia of the fetus, and there will be a manifestation of 18 days of blastocyst transplantation and vaginal bleeding all the time. 2. Ectopic pregnancy: no matter blastocyst, fresh embryo or frozen embryo, there may be ectopic pregnancy after transplantation, the gestational sac does not normally bed in the uterine cavity, such as bed in the fallopian tube area, with the increase of gestational weeks may rupture of tubal pregnancy, miscarriage, which manifests itself as abdominal pain, a small amount of persistent bleeding in the vagina. 3. Gynecological diseases: gynecological diseases such as cervicitis, endometritis, etc., stimulated by inflammation may cause vaginal bleeding all the time for 18 days after blastocyst transfer. If you keep bleeding after blastocyst transfer, you should go to the hospital to check the reason and see whether you can continue the pregnancy.