The main reason for breast swelling in pregnancy is the thousandfold increase of estrogen in the body, which leads to changes in the breasts, such as an increase in size, mild localized swelling and pain, and the present phenomenon of coloring of the nipples and areolas. In addition to blood tests for HCG and progesterone, it is recommended that ultrasound be done to check if the yolk sac can be seen in the gestational sac. Otherwise, it is recommended to check again after 5 days if you suspect that the embryo has stopped developing.