Pseudomenorrhea is the transmission of estrogen from the mother to the fetus at the end of pregnancy, and this endocrine hormone has the effect of stimulating the proliferation and congestion of the mucous membranes of the female infant’s reproductive tract. After birth, as the source of estrogen from the mother is interrupted, the concentration of estrogen in the baby girl’s body drops sharply, to a very low level after 3-5 days, and the supporting effect of estrogen on the proliferation and engorgement of the reproductive mucosa is interrupted. As a result, the endometrium, which had been proliferating and engorged with blood, is shed, resulting in a small amount of blood and bloody discharge from the vagina of the baby girl, which is similar to menstruation. It usually occurs 3-7 days after the birth of the baby and lasts for about a week, which is a normal physiological phenomenon and does not require any treatment.