Non-Invasive Management of Alloimmune Thrombocytopenia: Prediction of the Fetal Status.

Abstract 3690

Fetal/neonatal alloimmune thrombocytopenia (F/NAIT) is the most common cause of severe thrombocytopenia in the fetus and the newborn in maternity wards. To counter the bleeding consequences of severe fetal thrombocytopenia, antenatal therapies have been implemented for subsequent pregnancies with incompatible fetuses. Predictive parameters for fetal severe thrombocytopenia are important for the development of non-invasive strategy and tailored intervention. We report here data concerning 67 HPA-1bb women with 81 managed pregnancies with IVIG. In 51% of the cases, the diagnosis of F/NAIT was made during the first gestation, following an intracranial haemorrhage (ICH) in 8 cases (12%). Severe thrombocytopenia was recorded for 88% of the newborn. Analysis of the index cases did not show any correlation between the severity of the disease and the maternal genetic background (ABO group and HLA-DRB3 allele). Subsequent pregnancies were managed and therapy effectiveness was evaluated. The highest mean newborn plt count was observed for a combination of intravenous immunoglobulin (IVIG) and corticoids (135.10⁹/L; 54 newborn), in comparison with IVIG alone (89.10⁹/L; 27 newborn). No ICH was recorded in these 2 groups. The maternal anti HPA-1a antibody concentration measured before any treatment and before 28 weeks of gestation was predictive of the fetal status: a high antibody concentration (≥28 International Units/mL) was correlated with a severe thrombocytopenia of the fetus (p=0.0016). Follow-up of the antibody concentrations during 34 pregnancies with antenatal management allowed demonstrating for the first time that the areas under curves (AUC) weighted by the weeks of gestation were a predictive parameter of therapy failure. The weighted AUC was significantly higher for women who delivered severely thrombocytopenic newborn than newborn with platelet count above 50.10⁹/L (p=0.0107). To conclude, this large retrospective survey gives new insights on maternal predictive parameters for fetal status and therapy effectiveness allowing non-invasive strategies.