Fetal left renal collecting system separation of 8mm is an abnormal condition. In general, if the separation of fetal renal collecting system is within 10mm and there is no abnormality in the development of the fetus, there is usually no need for special treatment and regular review is sufficient. If the separation of the renal collecting system is more than 16mm, it is necessary to consider whether there are abnormalities in the development of the fetus’s urinary system, such as kidney, ureter, etc., and further examination is needed to determine this. Parents do not need to worry excessively if the separation of the left renal collecting system of the fetus is 8mm, but they need to consult a doctor in time if there are other abnormalities, such as ultrasound suggesting that the fetus has congenital renal anomalies, liver anomalies, and so on. Take into account the development of the fetus and the physical condition of the pregnant woman for the next step of examination and treatment.