The most common reasons for this are as follows: 1. The embryo may have bedded down on the 9th day after the transfer, and during the process of bedding down the embryo will erode the endometrium, so there will be brown discharge at this time. In this case, there is no need to worry, just pay attention to rest, the condition is often not serious. 2, the embryo may have successfully implanted after the transfer, but due to the quality of the embryo or the endometrial problem, the embryo failed to implant, that is, biochemical pregnancy, so at this time there will also be brown discharge. Therefore, in either case, it is necessary to take a blood test for HCG at this time, and depending on the specific result of HCG, it will be decided which treatment to use.