There is still a possibility of biochemistry after 40 days of transfer, which needs to be clarified by blood HCG test under the supervision of a doctor. Transfer refers to in vitro fertilization-embryo transfer technique, which is a kind of artificial assisted reproduction technology and must be operated by professional physicians. Generally the embryo can be implanted 3-4 days after the transfer, and the latest may be around 7 days. Biochemical pregnancy is a miscarriage caused by the failure of the embryo to implant, so there is still a possibility of biochemical pregnancy after 40 days of the transfer, which manifests itself in the appearance of vaginal bleeding similar to menstruation. When the embryo transfer should pay attention to appropriate rest, can not carry out strenuous exercise and heavy physical labor, continue to follow the doctor’s instructions luteal support therapy. Generally, blood or urine HCG (human chorionic gonadotropin) measurement can be carried out about 2 weeks after the transfer to confirm pregnancy. When vaginal bleeding occurs, it is necessary to go to the hospital in time to find out the cause and deal with it in time.