Severe fetal thrombocytopenia in Rhesus D alloimmunized pregnancies

OBJECTIVE: The objective of the study was to evaluate the incidence of fetal thrombocytopenia and association with hydrops in Rhesus D alloimmunization. STUDY DESIGN: The study was a retrospective chart review of 914 intrauterine transfusions in 314 pregnancies performed between 1988 and 2005 in a single institution. The incidence of thrombocytopenia and severity of hydrops at cordocentesis were assessed and correlated with perinatal mortality. RESULTS: Thrombocytopenia (less than 150 x 10(9)/L) was found in 241 of 914 (26%) and severe thrombocytopenia (less than 50 x 10(9)/L) in 25 of 914 (3%) cordocentesis. Twenty-three percent of severely hydropic fetuses had severe thrombocytopenia, compared with 3% and 1% of mildly hydropic and nonhydropic fetuses, respectively. Thrombocytopenia was an independent risk factor for perinatal mortality. Mortality in fetuses that were severely thrombocytopenic and severely hydropic was 67%. CONCLUSION: Thrombocytopenia is common in hydropic anemic fetuses. Severe thrombocytopenia is associated with a poor prognosis, irrespective of the presence of hydrops. The option of platelet transfusion in severely hydropic anemic fetuses needs further study.