The sudden ability to squeeze milk out of the breasts may be related to pregnancy, hyperprolactinemia, breast cancer and other diseases. 1. Pregnancy: After pregnancy, estrogen and progesterone in the body will increase, breasts will develop twice, and in the late stages of pregnancy, there will be milk secretion. 2. Hyperprolactinemia: Hyperprolactinemia is the abnormal elevation of serum prolactin caused by various reasons, which will lead to symptoms such as milk overflow, menstrual disorders, infertility and headache. 3. Breast Cancer: Breast cancer is a malignant tumor in which the epithelial cells of the breast proliferate out of control and become malignant. Symptoms of breast cancer include breast lump, breast skin abnormality, nipple overflow, nipple or areola abnormality and so on. In addition, breast hyperplasia, intraductal papilloma of the breast, non-lactating mastitis and other causes should also be considered.