After pregnancy, due to the increase of estrogen and progesterone levels in the body, the mammary glands will develop and with the increase of pregnancy weeks, the level of lactogen in the body will also gradually increase, which will cause the mammary glands to produce milk. When there is a small amount of lactation in the breast, pregnant women should not be nervous, pay attention to cleaning the nipple, do not cause infection, but pregnant women should not often stimulate the nipple, because through the nipple stimulation will cause an increase in endogenous secretion of contraction hormone, which may cause the symptoms of preterm labor, pregnant women should pay attention to wear loose and cotton underwear to reduce the stimulation of the mammary gland.