Abstract: Fetal hydronephrosis is one of the most common urinary tract finding on prenatal ultrasound diagnosis. With the popularity of prenatal ultrasonography and improvement of ultrasonic diagnosis technology，more fetal congenital malformations can be found. Fetal hydronephrosis has been divided into physiological and pathological hydronephrosis. Prenatal and postnatal management of hydronephrosis are both controversial. The prognosis of fetal hydronephrosis is closely related to etiology and degree of hydronephrosis.

Key words: Fetus, Hydronephrosis, Diagnosis, Therapy, Prognosis