The transfer may be blastocyst, fresh embryo or frozen embryo. Bleeding 18 days after the transfer may be caused by insufficient luteal support, miscarriage, ectopic pregnancy and cervical polyp. 1. Insufficient luteal support: after 18 days of transfer, the luteal support in the woman’s body is insufficient, and the endogenous and exogenous progesterone levels are relatively low, which will cause bleeding if it does not support pregnancy. 2. Miscarriage: 18 days after implantation due to poor embryo quality, excessive stress, anxiety and other reasons may cause fetal miscarriage, bleeding less, stomach pain and other symptoms. 3. Ectopic pregnancy: Whether it is blastocyst, fresh embryo or frozen embryo transfer, ectopic pregnancy may occur after the transfer, such as tubal pregnancy, etc. There may be vaginal bleeding after tubal rupture. 4. Cervical polyps: before the transfer of women suffering from cervical polyps, cervical polyps are generally chronic cervical inflammation long-term stimulation of hyperplasia produced by the proliferation of tissue, hyperplasia of the mucosa gradually protruding from the outside of the cervix, the surface of the microvessels are rich in microvessels, microvessel rupture after the transfer of 18 days may bleed. There are many reasons for bleeding on the 18th day of transplantation, so it is recommended to go to the doctor in time, complete the relevant examinations, clarify the causes under the guidance of professional doctors, and actively target treatment.