Separation of both kidneys at 37 weeks of pregnancy may be physiologic separation or pathologic separation such as the presence of hydronephrosis. Separation of both kidneys is the separation of the renal collecting system. If the bilateral separation is less than 10mm, it may be due to the fullness of the bladder and the urine is not discharged, which makes the renal pelvis fill up and become bigger, causing the separation of the renal pelvis, this is a physiological change, no need to worry too much. If the separation is greater than 10mm, then we should be alerted to the possibility of hydronephrosis, i.e., the development of the fetal urinary system is abnormal, there are structural deformities, the fetus can’t urinate normally, so the renal pelvis is dilated obviously, and the renal function is obviously impaired, thus resulting in the separation of the two kidneys is obvious. Low amniotic fluid may also occur in the late stage. It is recommended that abnormalities are detected during pregnancy, and the patient should seek medical attention for prenatal diagnosis and follow-up.