It is necessary to specify the type of bumps to further clarify the diagnosis: 1. Axillary sebaceous cyst due to the body burden during pregnancy, easy to sweat after activities, the axilla is often in a humid state, and the axillary sebaceous gland is prone to blockage for a long time. In milder cases, local disinfection with iodophor and attention to cleanliness and hygiene can be restored, but in serious cases, hospital consultation is needed. 2. Lymph node enlargement in the armpit caused by mastitis can be clearly diagnosed through ultrasound. 3. Lymph node metastasis of breast cancer, which can be asymptomatic in the early stage of breast cancer, can accelerate the growth of tumor and metastasize to the lymph nodes in the armpit due to the change of hormone level in the body during pregnancy. 4. Lymphoma, if there is a lump in the armpit with no obvious cause and no uncomfortable symptoms, it should be taken seriously and should be seen by a hospital in time, and if necessary, a puncture biopsy should be performed to clarify the diagnosis. Therefore, if you find a lump in your armpit during pregnancy, you must pay attention to it and go to the hospital in time to avoid delaying the condition.