Intravenous immunoglobulin (IVIG) treatment was attempted as a novel therapeutic approach for unexplained recurrent spontaneous abortions (RSA) occurring in the first trimester of pregnancy. Twenty women with a history of RSA were treated with IVIG during pregnancy. Therapy was commenced at week 5 of gestation with 1 dose of 0.5-0.6 g IVIG/kg body weight. Infusions were repeated every 3 weeks (0.3-0.4 g/kg) and terminated by week 22 to 24. Of 20 women, 11 delivered healthy infants at term. 5 women are still pregnant, 3 in the third trimester. Only 3 patients suffered abortions and 1 presented with ectopic pregnancy. The overall success rate was 82-86%. Thus, the therapeutic effect of IVIG is comparable to that of the conventional transfusion/vaccination regimen with allogeneic leukocytes, but avoids the risk of transmission of infections and/or HLA immunization, has no major adverse effects and is applicable to ‘nonresponders’.

In vivo immune phagocytosis of neonatal monocytes was significantly correlated to the extent of maternal HLA immunization. Monocytes from all 15 neonates of mothers with HLA antibodies show reduced immune phagocytosis. In contrast, this holds true for monocytes from only 6 out of 13 neonates of mothers without detectable HLA antibodies. We infer the hypothesis that maternal HLA antibodies bind to mononuclear phagocytes of the fetus and of the fetal part of the placenta and thus cause inhibition of immune phagocytosis. Thereby, activation and secondary cell or tissue injury will not ensue and rejection of the fetal allograft is prevented in those pregnancies in which maternal alloimmunization occurs.

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