The normal range of fetal hydronephrosis is <1.0cm. Ultrasound during pregnancy suggests fetal renal pelvic dilatation or hydronephrosis, can be observed under the guidance of the doctor for follow-up, generally when the renal pelvis dilatation of 0.5-1.0cm is mild, most of them are due to physiological reasons, usually no treatment is needed if there is no problem after birth, but the pregnancy needs to be dynamically rechecked, and also to monitor the amount of amniotic fluid, the bladder and kidney echogenicity, and so on. During pregnancy, you should follow the doctor's instructions to standardize the reasonable obstetric examination, can timely detect abnormal fetal development, the doctor will be based on dynamic observation to assess the intrauterine condition of the fetus, but also can give timely treatment advice. Standardized obstetrical examination can prevent and treat pregnancy complications at an early stage, assess the safety of the pregnant woman and the fetus, and confirm the timing and mode of delivery to ensure the safety of the mother and the child.