The first three days of conception are the first three days after intercourse after ovulation, when there is usually no obvious manifestation, and the early pregnancy reaction usually occurs around 6 weeks after menopause. After intercourse, the sperm passes through the uterine cavity into the fallopian tube and combines with the egg discharged by the woman to form a fertilized egg. This process takes one to two days. It takes five days to a week for the fertilized egg to reach the uterine cavity and settle in the uterus. During the period between the formation of the fertilized egg and its entry into the uterine cavity, the woman has no noticeable clinical symptoms. It is only after the fertilized egg has been deposited that the body begins to secrete HCG. Due to the gradual increase in HCG levels, a series of early pregnancy reactions, such as weakness, nausea, and morning sickness, may occur around six weeks after menopause. When these symptoms are mild, they generally do not require special treatment. After 12 weeks of pregnancy, with the decline of HCG in the body, the symptoms will disappear naturally and the appetite will gradually improve. Therefore, the first three days of conception usually have no obvious symptoms, women need to relax, and when abnormalities occur, consult a doctor in a timely manner.