Bleeding on the twelfth day of fresh embryo transfer may be caused by implantation bleeding, menstrual flow, ectopic pregnancy, etc. It can be treated by checking blood HCG and surgery. 1. Bleeding on implantation: some women may have blood vessel rupture when the implantation is successful on the twelve days of transfer, causing a small amount of bleeding, thus appearing a little bleeding on the twelve days of transferring fresh embryos, which is usually normal. At this time, blood can be drawn to check the level of human chorionic gonadotropin HCG, to clarify whether pregnancy. 2. The onset of menstruation: the luteal phase after ovulation is about fourteen days, bleeding occurs on the twelfth day after the transfer, if the amount of bleeding is the same as the amount of menstruation, it may be the decline of luteal function and the decline of estrogen and progesterone, which leads to the onset of menstruation, suggesting that it may be a failure of the transfer. At this time, blood can also be drawn to check the HCG level, to clarify whether it is the onset of menstruation. 3. Ectopic pregnancy: If the bleeding of the pregnant woman is less than the menstrual flow, and the examination finds that the HCG value is low, it is considered that it may be ectopic pregnancy. Blood HCG monitoring and pregnancy ultrasound should be performed to observe the location of the gestational sac. If ectopic pregnancy is present, treatment such as surgery as prescribed by the doctor may be considered. If a woman has a bit of bleeding twelve days after the transfer of fresh embryos, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or standardized treatment.