Fetal alloimmune thrombocytopenia and maternal intravenous immunoglobulin infusion

Abstract

Background: Different therapeutic approaches have been used in fetal-neonatal alloimmune thrombocytopenia, but many centers administer immunoglobulin G infusions to the pregnant woman. We studied the effect of maternal antenatal immunoglobulin infusions on fetal platelet counts in pregnancies with fetal alloimmune thrombocytopenia.

Design and methods: We retrospectively analyzed the clinical courses of fetuses with fetal alloimmune thrombocytopenia whose mothers were treated with immunoglobulin G infusions in a single center between 1999 and 2005. In a center-specific protocol, weekly maternal immunoglobulin G infusions were given to 25 pregnant women with previously affected neonates and four women with strong platelet antibodies, but no previous history of fetal alloimmune thrombocytopenia; before each infusion diagnostic fetal blood sampling was performed to determine fetal platelet counts and immunoglobulin G levels.

Results: There were 30 fetuses with fetal alloimmune thrombocytopenia, confirmed by initial fetal blood sampling showing fetal platelet counts between 4×10(9)/L and 130×10(9)/L and antibody-coated fetal platelets using a glycoprotein specific assay. Despite weekly antenatal maternal immunoglobulin G infusions fetal platelet counts did not change significantly. Maternal and fetal immunoglobulin G levels, measured before every infusion, increased significantly with the number of maternal immunoglobulin G infusions.

Conclusions: In this group of fetuses with fetal alloimmune thrombocytopenia no consistent increase of fetal platelets was achieved as a result of regular maternal immunoglobulin G infusions.

Figure 1.

Platelet counts in 30 fetuses with fetal alloimmune thrombocytopenia whose mothers received weekly intravenous immunoglobulin G. There was a trend towards a decrease in fetal platelet counts during weekly maternal immunoglobulin G infusions. The dashed lines indicate fetuses with an initial platelet count ≤20x10⁹/L, the dotted lines fetuses with higher starting values which then fell to ≤20x10⁹/L; solid lines indicate all other fetuses.

Figure 2.

Mean platelet counts (actual values and statistical model) in fetuses with alloimmune thrombocytopenia, whose mothers were treated with intravenous immunoglobulin G, between 23 and 34 weeks’ gestation. The X symbols indicate mean values of the raw data, the solid line indicates the mean values from the maximum likelihood estimation and the vertical bars indicate the 95% confidence intervals for each week’s estimate.