Gestational thrombocytopenia and immune thrombocytopenias in pregnancy.

Appropriate management of thrombocytopenia in the pregnant patient is important for the well-being of both mother and fetus. The healthy-appearing mother with mild thrombocytopenia may have either gestational benign thrombocytopenia, which does not produce fetal thrombocytopenia, or immune-mediated thrombocytopenia, which can produce fetal thrombocytopenia. These two types of pregnancy-associated thrombocytopenias can be differentiated. Gestational benign thrombocytopenia is initially discovered during pregnancy, and in these patients a reliable test for antiplatelet antibody is usually negative. Conversely, patients with immune-mediated thrombocytopenia may have a history of thrombocytopenia before the pregnancy, and these patients usually have a detectable antiplatelet antibody. The pregnancy patient who presents with a normal platelet count and a history of neonatal alloimmune thrombocytopenia in a prior pregnancy or with a history of an infant of a close relative with NAT must be carefully monitored. Antiplatelet antibody assays performed on mother's and baby's blood will help determine if an antiplatelet antibody is present in maternal plasma, if the antibody reacts with the baby's platelets, and (with appropriate typing plasma) the antigenic specificity of the maternal and fetal platelets. In addition, antigenic typing of the father's platelets will help determine the risk of NAT in the current pregnancy. If a fetus is at risk for severe immune-mediated thrombocytopenia from either an autoantibody or an alloantibody, the fetal platelet count should be measured, if possible, from blood obtained by umbilical cord puncture. If the fetal platelet count is less than 50,000/microL or cannot be measured but is thought to have a high probability of being less than 50,000/microL, strong consideration should be given to a cesarean delivery.