The fertilized egg is still in the state of germ cells, so it is not possible to cause bilateral breast swelling and pain immediately. Although the trophoblast cells start to secrete blood HCG after the fertilized egg is deposited, the concentration is relatively small at the beginning, so it is not enough to cause bilateral breast swelling and pain. With the further progress of pregnancy, the gradual growth of the fetus, blood HCG and estrogen secretion will gradually increase, so that there will be some corresponding clinical symptoms, about 6 weeks after menopause will appear localized breast swelling and pain, breast enlargement, and nipple and areola coloring phenomenon, this is a normal reaction to early pregnancy is a physiological phenomenon, no need to be nervous, it is recommended to do a good job in the local care of the breasts.