The prenatal prediction of thrombocytopenia in infants of mothers with clinically diagnosed immune thrombocytopenia.

The management of the pregnant patient with immune thrombocytopenia is complicated by the unavailability of the fetal platelet count. Since the transplacental passage of antiplatelet antibodies mediates infant thrombocytopenia, measurement of maternal platelet-associated IgG might predict infant outcome. We related the maternal platelet count and platelet-associated IgG level to the infant's platelet count in 41 pregnancies in 38 patients who were clinically diagnosed as having immune thrombocytopenia. Fifteen of 39 live-born infants were thrombocytopenic at delivery. Maternal platelet-associated IgG was predictive of infant platelet count but maternal platelet count was not; only one of the 20 infants delivered of the 18 thrombocytopenic mothers with normal platelet-associated IgG was affected, whereas 11 of 12 thrombocytopenic mothers with elevated platelet-associated IgG had thrombocytopenic infants. Five infants died in utero between 18 and 28 weeks' gestation, but otherwise there was no significant morbidity in the live births. Measurement of platelet associated IgG in mothers with immune thrombocytopenia during pregnancy can be used to predict infant thrombocytopenia, although it does not predict the severity of the thrombocytopenia.