Separation of the renal pelvis at 16 weeks and less than 1.0 cm usually does not require amniocentesis, which is recommended when combined with other anomalies and renal pelvic dilatation greater than 1.0 cm. Fetal renal pelvis separation is used as an ultrasound soft indicator of chromosomal abnormality. Isolated renal pelvis separation does not increase the risk of chromosomal abnormality, and most of them are physiologic. If the ultrasound at 16 to 18 weeks suggests that the fetal renal pelvis is separated by less than 1.0 cm, it is often physiologic. If the separation of the renal pelvis is more than 1.0 cm, the prenatal diagnosis center should be consulted to determine whether amniocentesis is necessary. When the ultrasound suggests that the renal pelvis separation is 0.4~1.0cm, most of them will disappear gradually; when the renal pelvis separation is more than 1.0cm, the chances of pathological changes of the kidney increase, and most of the experts suggest that the baby should be rechecked 5~7 days after delivery. Don’t panic when the maternity test during pregnancy suggests fetal renal pelvis separation, you can consult a professional obstetrician to exclude pathological changes and review regularly.