The leukorrhea in 3-month-old baby girls is mainly due to the influence of maternal estrogen in the fetus. The high estrogen level of the mother causes the estrogen level in the baby to rise, which can lead to leukorrhea, and some baby girls will have menstrual blood soon after birth, and some baby girls will have long breasts due to the influence of high estrogen level of the mother. The leukorrhea usually lasts for about 3-6 months and can disappear on its own, menstrual bleeding is usually within a month, and the phenomenon of growing breasts usually lasts until about 2 weeks of age, with some disappearing without treatment. If your child’s symptoms are recurrent or the leukorrhea continues to persist, you should go to the hospital for blood hormone related tests.