Breast swelling and pain after embryo transfer is due to the fact that the embryo is alive after the transfer, the chorionic gonadotropin level in the pregnant woman’s body will increase, and the pituitary gland will start to secrete prolactin. In this case, the woman’s breasts will start to develop, and the ducts and breast tissue will develop, further increasing the size of the breasts and causing them to swell and hurt. The breasts will increase significantly after pregnancy, mainly to prepare for breastfeeding later, so the breast swelling and pain will usually occur after a successful transplant. In addition, the breasts will remain relatively large during pregnancy and this state will continue until the end of breastfeeding.