Vague stomach pain on the sixth day of transfer may be caused by embryo implantation or by the use of progesterone medication. If the abdominal pain worsens and there is redness in the vagina, the possibility of transfer failure cannot be ruled out. Embryo implantation is the process of embryo slowly buried in the endometrium, which may cause abdominal discomfort during the process. During the embryo transfer process, doctors will use progesterone drugs to replenish the progesterone in the body to provide a suitable internal environment for IVF transfer. Progesterone drugs may cause symptoms of vague pain in the small abdomen after use, and it is recommended to pay attention to the changes in abdominal pain, if the symptoms worsen and are accompanied by vaginal bleeding, miscarriage may occur.