Breast swelling usually occurs in the early stages of pregnancy at 3~4 weeks after conception and varies from person to person. In general, most women will have breast swelling and pain in the early stage of pregnancy, which is more common at around 3~4 weeks of pregnancy, but some women may experience it earlier than the early pregnancy reaction, and the symptom will be gradually reduced when the early pregnancy is over, which is mainly due to the hormone level of the body gradually stabilizes during pregnancy. If breast swelling occurs during pregnancy, it is normal and does not require special treatment. However, if the swelling and pain is strong and getting more and more serious, it may be caused by mastitis or other mammary gland diseases, in which case you should consult a doctor in time and get targeted treatment.