During pregnancy and lactation, due to the influence of pituitary prolactin, placental lactogen, estrogen, progesterone, growth hormone and insulin, there will be hyperplasia and fat deposition in the milk ducts and alveoli, making pregnant women feel swollen breasts, feeling painful to touch and tingling, as well as enlarged and darkened nipples, easy erection, and darkened areolas, and sebaceous glands on the areola form small scattered nodular bulges, and squeezing at the end of pregnancy If you squeeze your breasts at the end of pregnancy, a small amount of thin yellow fluid may spill out, called colostrum. Therefore, the tingling in the breast during breastfeeding is a tingling-like sensation caused by the hormonal effect of breast enlargement, fatty deposits in the breast, and the enlargement of the breast.