There are several reasons for menstruation after transfer: the first one is inflammation of the cervical canal with brittle texture and contact bleeding, when the transfer tube enters the uterine cavity, there may be a small amount of damage to the mucosa of the cervical canal when it passes through, so it causes bleeding. The second kind is that the transferred blastocysts are born in 1-2 days, and the embryos on the third day of transfer are born in 3-4 days, and some of them will have a small amount of vaginal bleeding when they are born, so this is also the cause of vaginal bleeding after transfer. The third one is a kind of withdrawal bleeding caused by stopping or missing the medication after the transfer. After this situation occurs, timely replenishment of the missed medication will basically have no effect on pregnancy. Therefore, all of these cases do not affect the pregnancy too much, so don’t worry too much, just keep observing, keep taking the medication and wait for the pregnancy test.