4 months baby urine yellow, may be due to physiological or pathological factors, physiological factors such as drinking less water; pathological factors such as infections, etc., can lead to the phenomenon of yellow urine baby. 1. physiological factors: when the baby has too little water, excessive sweating, etc., the body water is reduced, the urine is concentrated, so the phenomenon of yellow urine. 2. Pathological factors: there are urinary tract infections such as acute pyelonephritis, which leads to yellow urine; in addition, there are jaundiced babies, the blood bilirubin metabolized by the kidneys after the discharge, there will also be yellow urine phenomenon. 4 months baby urine yellow, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.