There are several causes of nipple crusting in pregnant women: 1. The most common may be because of gynecological diseases such as acute mastitis, or acute breast cysts. Acute mastitis, in particular, is one of the most important causes of nipple crusting in pregnant women. Because a woman’s hormone levels change significantly during pregnancy and her body is in a weaker state, she is susceptible to infection by external bacteria. For example, Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, and Gram-positive bacteria, when these bacteria infect the nipples of pregnant women, they can lead to an inflammatory reaction in the nipples. This leads to an increase in the permeability of blood vessels and the exudation of inflammatory substances, which accumulate on the skin surface of the nipples and form crusts over time.2. It may be due to a disorder in the endocrine system of women, because the level of various hormones such as estrogen and sex hormones in women’s bodies during pregnancy will have a great change, which will lead to an obstacle in the elimination of metabolic substances from the body, and some foreign substances can accumulate Some foreign substances can accumulate on the surface of the nipples, leading to crusting of the nipples of pregnant women.