There are several possible reasons for sore nipples in pregnancy: first, the development of the breasts accelerates in the period after pregnancy. At this time there will be a certain amount of milk accumulated in the breast cells to prepare nutrition in advance for the birth of the fetus. Due to the increased size of breast cells, it will press the nerves around the breast to make people feel pain. This is a normal physiological phenomenon, not a sign of disease. Second, it may be inflammation of the mammary gland. Because a woman’s body is in a sensitized state during pregnancy, her resistance is relatively weak. This time, coupled with the relative instability of the body’s endocrine system, can lead to external germs infecting the breast. If the breast is infected by bacteria, it will lead to redness, swelling, distension and pain in the breast, and also cause pain in the nipple, which will need to take certain medicines for treatment. Thirdly, it may also be caused by breast enlargement. Nowadays, the number of women with breast enlargement is increasing, and pregnant women are also prone to breast enlargement, which can also cause nipple pain.