Before giving birth, it was menstruation. After conception, the milk began not to flow downwards, but to gather to support the children in the womb. Children grow up in the mother's body and begin to become milk to feed their children after birth. It doesn't turn into menstruation until after returning to milk.
Chinese medicine says: milk is transformed from subtle qi and blood through the spleen and stomach, and then distributed to the two breasts by the lungs, and then the heart restrains the lungs and releases the milk from the nipple. So we often see that the color of milk will change. Colostrum is yellow (because the milk source is spleen), and then it becomes white (because the lungs are white, mainly for blood transfusion).
For some women who are not particularly well, we will also see that the milk is pink or red, which is caused by the decline of heart ability or the unfavorable distribution of lungs.
When you are not pregnant, your body will still release milk, from top to bottom. Therefore, in the days when menstruation comes, the breasts will feel a little full, and then the milk will slowly reach the uterus through the pulse condition and ren meridian. The uterus is in front of the small intestine, and the heating of the small intestine will turn the milk from white to red. So what comes out is red menstruation. If the small intestine fire is low, the color of menstruation will fade. The greater the fire in the small intestine, the darker the color of menstruation.
This is the ins and outs of milk!