Objective:To evaluate the clinical efficacy of conventional tocolytic therapy combined with passive immunoglobulin immunotherapy in blocking antibody（BA）-negative recurrent spontaneous abortion（RSA） patients.Methods:A total of 108 RSA patients in early pregnancy who were admitted to our hospital from January 2018 to April 2019 were randomly divided into control group and observation group.The control group was treated with conventional tocolytic therapy

and the observation group was given conventional tocolytic therapy plus passive immunoglobulin immunotherapy.Post-treatment serum β-HCG and progesterone levels were monitored at weeks 6

8

and11 of pregnancy in the two groups.Ultrasound was performed regularly to monitor embryo development.Changes in the percentages of CD19

+

NK

CD3

+

CD4

+

and CD8

+

cells after treatment were examined and compared between the two groups.Pregnancy success rate and adverse reaction rate were compared between the two groups.Results:At weeks 6

8

and 11 of pregnancy

serum β-HCG and progesterone levels were significantly higher in the observation group than in the control group（P

<

0.05）.The changes in the percentages of CD 19

+

NK

CD3

+

CD4

+

and CD8

+

cells after treatment were significantly lower in the control group than in the observation group（P

<

0.05）（Table 2）.The pregnancy success rate was significantly higher in the observation group than in the control group（81.48% vs44.44%

P

<

0.05）.However

there was no significant difference in the adverse reaction rate between the control group（13 cases

24.07%） and the observation group（14 cases

25.93%）（P

>

0.05）.Conclusion:Conventional tocolytic therapy combined with passive immunoglobulin immunotherapy can improve the pregnancy success rate and immune parameters of BA-negative RSA patients

and may therefore be an effective clinical treatment for RAS.