Pregnancy breast swelling and pain for a few days suddenly no pain is may be physiological reasons, pathological reasons, etc. Causes. 1. Physiological reasons: after pregnancy breast pain is caused by increased levels of estrogen and progesterone in the body, some women due to hormonal changes caused by the response is not strong, so there can be a sudden disappearance of the phenomenon of breast pain, if ultrasound and blood hCG (human chorionic gonadotropin) and progesterone tests are normal, do not have to worry about it. 2. Pathological reasons: when there are abnormalities such as fetal termination, the level of estrogen and progesterone in the body also declined rapidly, so that the phenomenon of breast swelling and pain suddenly disappeared, in accordance with the doctor’s instructions for ultrasound, blood hCG and progesterone test can assist in the diagnosis, the need to terminate the pregnancy in a timely manner. When pregnant breast swelling pain for a few days suddenly no pain when you need to go to the hospital in time, under the guidance of the doctor to find the cause, and actively deal with.