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 cause leukorrhea. The symptoms of leukorrhea usually last about 3-6 months and can disappear on their own, menstrual bleeding is usually within a month, and the phenomenon of long breasts usually lasts until about 2 weeks of age, with individual cases disappearing without treatment. If your child’s symptoms are recurrent or the leukorrhea continues to persist, you will need to go to the hospital for some relevant tests.