Brown discharge and tingling sensation on the sixth day after frozen embryo transfer may be caused by irritation of the endometrium by embryo transfer, unstable entry of the embryo into the uterus, insufficient luteal secretion or unsuccessful transfer. 1. Embryo transfer into the uterine lining will destroy the fine blood vessels within the lining, causing a small amount of bleeding and abdominal pain. 2. Embryo instability, where the embryo enters the uterus for a short period of time before it grows firmly in the endometrium, can also cause this small amount of brown discharge or tingling. 3. Insufficient corpus luteum secretion is mainly due to the low secretion of progesterone in the body during pregnancy, which is unable to maintain the development of the embryo in the uterus and may also cause a small amount of brown discharge. 4. Brown discharge on the sixth day of embryo transfer may also be caused by transfer failure, that is, there is no substantial development in the uterine cavity. If the amount of brown discharge is not much and the tingling sensation is mild, you need to rest more and use medication to protect the fetus, such as progesterone. If it lasts for a long time or if the abdominal pain increases, it is important to consult the doctor to see if other medications are needed to avoid delaying the condition.