Thrombocytopenia in pregnancy

Abstract

Thrombocytopenia develops in 5% to 10% of women during pregnancy or in the immediate postpartum period. A low platelet count is often an incidental feature, but it might also provide a biomarker of a coexisting systemic or gestational disorder and a potential reason for a maternal intervention or treatment that might pose harm to the fetus. This chapter reflects our approach to these issues with an emphasis on advances made over the past 5 to 10 years in understanding and managing the more common causes of thrombocytopenia in pregnancy. Recent trends in the management of immune thrombocytopenia translate into more women contemplating pregnancy while on treatment with thrombopoietin receptor agonists, rituximab, or mycophenylate, which pose known or unknown risks to the fetus. New criteria to diagnose preeclampsia, judicious reliance on measurement of ADAMTS13 to make management decisions in suspected thrombotic thrombocytopenic purpura, new evidence supporting the efficacy and safety of anticomplement therapy for atypical hemolytic uremic syndrome during pregnancy, and implications of thrombotic microangiopathies for subsequent pregnancies are evolving rapidly. The goals of the chapter are to help the hematology consultant work through the differential diagnosis of thrombocytopenia in pregnancy based on trimester of presentation, severity of thrombocytopenia, and coincident clinical and laboratory manifestations, and to provide guidance for dealing with some of the more common and difficult diagnostic and management decisions.

Figure 1.

Prevalence of causes of thrombocytopenia based on trimester of presentation and platelet count. The size of each circle represents the relative frequency of all causes of thrombocytopenia during each of the 3 trimesters of pregnancy. All etiologies and all platelet counts are considered together in the first trimester when thrombocytopenia is uncommon. Distribution of etiologies during the second and third trimesters is subdivided by platelet count. All results are estimates based on personal experience and review of the literature. “Other” indicates miscellaneous disorders, including infection, DIC, type IIB von Willebrand disease, immune and nonimmune drug-induced thrombocytopenia, paroxysmal nocturnal hemoglobinuria, bone marrow failure syndromes (aplastic anemia, myelodysplasia, myeloproliferative disorders, leukemia/lymphoma, and marrow infiltrative disorders), among others. HUS, hemolytic uremic syndrome; PEC, preeclampsia/HELLP; TTP, thrombotic thrombocytopenic purpura.

Figure 2.

Distribution of platelet counts in healthy pregnant women at term. Reprinted from Boehlen et al with permission.