Relationships between severe neonatal thrombocytopenia and maternal characteristics in pregnancies associated with autoimmune thrombocytopenia.

In pregnant women with antecedents of autoimmune thrombocytopenia (AITP), no predictive factor for severe fetal thrombocytopenia has been identified. We evaluated the relationships between the course of the maternal disease before and during pregnancy and the risk of severe fetal thrombocytopenia, in 64 pregnant women with known chronic AITP antecedents, over a 12-year period. 28 pregnant women had undergone splenectomy before pregnancy and 17 experienced severe thrombocytopenia (< 50 x 10(9)/l) during pregnancy (monthly determination). Eight infants presented with severe thrombocytopenia at birth (12.5%), and four in the following days (6.25%). No severe haemorrhage was observed. Severe thrombocytopenia at birth was present in 57% (CI 95% 18-90%) of the infants born to mothers with severe pregnancy-associated thrombocytopenia and splenectomy antecedents, and in 0% (CI 95% 0-15%) of the infants born to mothers who presented none of these antecedents (P=0.001). In thrombocytopenic mothers the infant platelet counts at birth were positively correlated to the nadir maternal platelet count during the index pregnancy (r=0.42, P=0.0075). These results suggest that severe autoimmune disease is a risk factor for severe fetal thrombocytopenia, and that pregnant women with no antecedent of splenectomy nor severe thrombocytopenia during pregnancy have a very low risk of severe fetal thrombocytopenia.