How many days after fertilization does the embryo implant, and what reactions occur?

The fertilized egg typically implants in the uterus 6 to 7 days after fertilization. During implantation, the fertilized egg moves into the uterine cavity and embeds itself into the endometrium, beginning to establish a connection with the mother. Women may experience a series of physical responses during this process. First, breasts may become tender and sore due to rising levels of progesterone and estrogen. Second, some women may notice light vaginal bleeding or blood-tinged discharge, caused by the invasion of the fertilized egg into the endometrial lining. Additionally, implantation may lead to a slight increase in body temperature of 0.2°C to 0.5°C, as well as mild abdominal cramping and general fatigue. These symptoms usually indicate that the fertilized egg has successfully implanted, marking the beginning of early pregnancy.