Abstract： Objective To explore the clinical significance of prenatal ultrasonic diagnosis of fetal nephrohydrosis and its prognosis.Methods Prenatal ultrasanography was performed on 9526 women at more than 20 weeks gestation,and 162 women whose anteroposterior diameter of the renal pelvis was≥8 mm were included in this study.The grade of fetal nephrohydrosis was classified according to Grignon grading method.The changes in fetal nephrohydrosis were observed regularly until delivery.Results(1)The incidence of fetal encephalic fluid and Grignon grade:there were 162 fetuses with fetal nephrohydrosis among 9526 fetuses,with an incidence of 1.7%.The numbers of fetuses with Grades 1 to 5 were 71,59,7,3 and 22,respectively.(2)The distribution in gestafional weeks of fetal nephrohydrosis:generally,fetal nephrohydrosis was first diagnosed at(33±5)weeks,and the maximum degree of nephrohydrosis was observed at(36±3)weeks.One hundred and ten fetuses with nephrohydrosis recovered during the process of gestation,at about(37±4)weeks.(3)Poor terminations of pregnancy:there were 40(25%)fetuses with poor terminations among totally 162 cases.Among these 40 fetuses,3(27%)were first diagnosed at 20 to 24 weeks within 11 fetuses,6(24%)were first diagnosed at 25 to 28 weeks within 20 fetuses,14(26%)were first diagnosed at 29 to 32 weeks within 53 fetuses,11(23%)were first diagnosed at 33 to 36 weeks within 48 fetuses,and 6(20%)were first diagnosed at 37 to 40 weeks within 30 fetuses,The results demonstrate that high grade of fetal nephrohydrosis according to Grignon grading method indicates a poorer prognosis of the fetus.(4)Follow-up results:there were 122(75%,122/162)live and healthy neonates in total,including 110 neonates whose nephrohydrosis recovered prior to birth and 12 neonates whose nephrohydrosis recovered within 1 week after birth.These neonates all developed well without any urinary sequela within the first 2 years.There were also 20(12%,20/162)hydronephrotic neonates who were still diagnosed as nephrohydrosis within 1 week after birth,including 11 fetuses graded below Grignon grade 3,whose nephrohydrosis recovered 3 to 12 months after birth and who developed well without any urinary symptoms.Conclusions The study demonstrates that hydronephrotic fetuses who are diagnosed at earlier gestational weeka and with higher grading have poore prognosis.The Grignon grading method can be used in the prenatal evaluation of fetal nephrohydrosis to predict the prognosis of the fetus.