Whether the separation of the renal pelvis of the fetus is dangerous or not is mainly related to the width of the separation of the renal pelvis, if the separation of the renal pelvis is within 10 millimeters the danger is low, if it is more than 10 mm, it may be dangerous. When a woman is pregnant, the level of progesterone in her body rises, which can cause the smooth muscle of the ureter to expand to a certain extent, and the separation of the renal pelvis is shown under ultrasound detection. If it is under 10mm, it does not need to be treated, and regular ultrasound review can be done, and most of the newborn babies can recover on their own after urination. If the separation of the renal pelvis is more than 10 mm, secondary dilatation of the renal calyces may occur in severe cases, and hydrocele may be treated by decompression of the renal pelvis with catheter placement via uterine puncture or by pyeloplasty after birth. When a pregnant woman learns that her fetus has a separated renal pelvis, she can go to a specialist hospital for a review to detect the progress of the disease.