The sudden disappearance of breast swelling and pain in the early stages of pregnancy may be due to physiological reasons, or it may also be caused by embryonic arrest. 1. Physiological reasons: After pregnancy, the estrogen in the body will gradually rise to about three months will reach the peak, during this period, under the action of estrogen, pregnant women will have a feeling of swelling and pain in the chest. After three months, the hormone level gradually stabilizes, and the breast swelling phenomenon will disappear. 2. Embryo termination: If a pregnant woman finds that her breast swelling and pain suddenly disappears, and other pregnancy reactions such as nausea, vomiting and bloating also stop, it may be caused by embryo termination. When a pregnant woman finds that her chest swelling and pain disappears, she should go to the hospital in time for examination to clarify the cause, and if it is embryonic sterilizations, she needs to be treated under the guidance of the doctor.