This patient should receive HLA-matched platelets. She meets criteria for platelet transfusion refractoriness, defined as an increase in the platelet count less than 10,000/µL (10 × 10⁹/L) measured 10 to 60 minutes after transfusion on at least two separate occasions. Nonimmune causes include sepsis, fever, disseminated intravascular coagulation, splenomegaly, and medications that decrease platelet half-life. This patient has no features suggesting a nonimmune cause. She is most likely alloimmunized from her previous pregnancies. Such patients are ideally treated with HLA-matched platelets. A systematic review demonstrated improved 1-hour posttransfusion platelet counts with HLA typing. However, the effects on 24-hour platelet counts were more varied, and the impact of this practice on bleeding and mortality is unclear. If HLA-matched platelets are not available, other strategies can be used, including transfusion of HLA-compatible platelets, in which the transfused platelets are missing the antigen to which the patient's alloantibodies are directed, or platelet crossmatching, in which the patient's serum is incubated with donor platelets.

ABO-matched platelets lead to a slightly higher platelet increment in patients who are not alloimmunized but are not likely to have a significant impact on someone who is truly alloimmunized.

Washed platelets are typically reserved for patients who have had severe allergic reactions to platelet transfusion (such as patients who are IgA deficient).

Studies have shown that prophylactic platelet transfusion for a platelet count less than 10,000/µL (10 × 10⁹/L) is superior to platelet transfusions administered at the onset of clinical bleeding, thus decreasing the incidence of clinically significant bleeding. As such, observation without platelet transfusion is inappropriate.