Objective To investigate the outcomes of fetuses with hemolytic anemia caused by red cell alloimmunization following intrauterine transfusion (IUT),and to analyze the influence of hydrops fetalis on IUT treatment.Methods A retrospective analysis was conducted on 70 fetuses,who were admitted to the Fetal Medicine Center,the First Affiliated Hospital of Sun Yat-sen University from January 2005 to May 2018,with hemolytic disease requiring IUT.Clinical data of the fetuses and the gravidas were collected and divided into hydrops group (17 cases) and non-hydrops group (53 cases) based on their conditions before IUT.Results of routine blood tests before and after the first IUT,gestational age at the first IUT,prognosis and outcomes of the fetuses were compared between two groups.t-test,rank-sum test,Chi-square test (or Fisher's exact test) and multivariant logistic regression analysis were used for data analysis.Results Totally,the 70 fetuses underwent 231 times of IUT.Compared with the non-hydrops group,the hydrops group had a significantly increased incidence of severe anemia [14/17 vs 47.2％ (25/53),x2=6.458,P=0.011],but decreased hemoglobin [(38.5 ± 21.4) vs (68.7± 19.3) g/L,t=5.471,P＜0.001] and hematocrit level [0.110 (0.044-0.246) vs 0.222 (0.077-0.299),Z=-4.390,P＜0.001] before the first IUT.After the IUT,the survival rate of the fetuses in hydrops group was significantly lower than that of the non-hydrops group [11/15 vs 94.3％ (50/53),P=0.038].There was no significant difference in gestational age at birth,birth weight,neonatal hemoglobin level at birth,the incidence of exchange transfusion,the number of blood transfusions required or the incidence of severe neonatal complication between the two groups (all P＞0.05).Logistic regression analysis indicated that the fetal hydrops was an independent risk factor for fetal survival (OR=12.8,95％CI:1.2-136.4,P=0.035).Conclusions Hydrops fetalis might reduce the survival rate of fetal hemolytic disease after 1UT.