The vast majority of women do not show the appropriate clinical response until about 25 days after fertilization, because after fertilization, the fertilized egg has to enter the uterine cavity under the peristaltic movement of the fallopian tube, and it has to travel for about an average of 9-13 days before it reaches the uterine cavity. After entering the uterine cavity, it doesn’t immediately implant, it has to swim for 2-3 days before implanting. It is only after implantation that the trophoblast cells begin to secrete blood HCG, and it is only with the increase in blood HCG and estrogen that the corresponding clinical response gradually occurs. In most cases, nausea, vomiting and other clinical reactions to early pregnancy will not occur until about 45 days after menopause. It is recommended not to be nervous if these reactions occur, as they are normal physiological phenomena. Due to individual differences, the reactions after pregnancy are not the same, some are mild, some are relatively serious.