Early pregnancy breast swelling and pain is considered to be caused by hormonal changes, which is normal. Secondly, it may also be caused by breast hyperplasia, breast tumor and other diseases. 1. Normal: After pregnancy, due to hormonal changes in the body, estrogen and progesterone will stimulate the proliferation of ductal cells and alveolar cells in the mammary glands, resulting in the phenomenon of breast swelling and pain. 2. Breast hyperplasia: the cause of breast hyperplasia is mainly related to endocrine disorders, such as estrogen-progestin ratio imbalance, abnormal quality and quantity of breast sex hormone receptors, etc., and the patient will have breast pain, nodules and other symptoms, and the nature of pain can be swelling and pain. 3. Breast tumor: Breast tumor is a tumor that occurs in the breast, which is most often manifested as breast lumps, and some patients also have breast swelling and pain. The cause of breast tumor is not clear yet, but may be related to estrogen over stimulation and genetic factors. There are many reasons for breast swelling and pain in early pregnancy, so patients are advised to go to the hospital for examination, make a clear diagnosis, and actively cooperate with doctors for standardized treatment.