The normal value of fetal bilateral renal pelvis separation is generally required to be no more than 10mm. Fetal bilateral renal pelvis separation at less than 10mm is mostly a physiological phenomenon, usually related to the fetus holding urine. Generally, no special treatment is needed and regular observation is sufficient. If the fetal bilateral renal pelvis separation index is more than 10mm, it is considered that there is hydronephrosis, if it is a small amount of hydronephrosis, the effect is not big. However, if the amount of hydronephrosis is relatively large, we should be vigilant for urinary malformation, and then we need to cooperate with amniocentesis and non-invasive DNA examination to analyze the development of the embryo and exclude embryonic malformation in time. If the separation of bilateral renal pelvis is detected, it is necessary to combine with other examinations to determine the development of the fetus, including Down’s syndrome screening and 4D ultrasound examination. Once the embryo is found to have developmental problems or congenital malformations, the pregnancy should be terminated as soon as possible.