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    Thrombocytopenia in pregnancy: Differential diagnosis can be life-saving

    When the platelet count drops, separating benign from life-threatening causes can prove quite challenging. Two experts explain the differences between gestational thrombocytopenia, heparin-induced thrombocytopenia, disseminated intravascular coagulopathy, idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, and other disorders.

    When a prenatal screening report tells you that a patient's platelet count is low, sorting out the differential diagnosis of this bleeding disorder can seem daunting. Is it a relatively benign problem like gestational thrombocytopenia or a less common disorder that can lead to life-threatening bleeding, such as disseminated intravascular coagulation (DIC) or acute fatty liver? Our goal here is to clarify the path to an accurate diagnosis.

    Thrombocytopenia affects roughly one in 10 pregnant women, making it a leading reason for ob/gyns to consult a perinatal hematologist.1 The normal range of platelet counts is from 150,000 to 400,000/μL in the nonpregnant woman and may be slightly lower in pregnant women secondary to greater expansion of their plasma volume, RBC, and platelet number, with resultant hemodilution.

    The obvious concern with thrombocytopenia during pregnancy is significant bleeding at the time of vaginal or cesarean delivery. Fortunately, such bleeding complications are uncommon unless the platelet count is less than 50,000/μL at the time of surgery or delivery.2,3 Early signs of a low platelet count include gingival bleeding, epistaxis, petechiae, and easy bruising. However, in the absence of trauma or surgery, significant bleeding is rare unless platelet counts are less than 10,000/μL.

    TABLE 1: Causes of thrombocytopenia in pregnancy
    There are many causes of thrombocytopenia in pregnancy but all are due to either increased platelet destruction or decreased platelet production (Table 1). Culprits that can decrease production of platelets are infections, diets deficient in folic acid, and hematologic disorders such as leukemia and aplastic anemia.3,4 But immunologic platelet destruction or thrombocytopenia from excessive bleeding or consumption occurs much more frequently.

    TABLE 2: Baseline evaluation for thrombocytopenia in pregnancy
    The minimum work-up for maternal thrombocytopenia should include a detailed history and physical exam with review of current medications, a complete blood count, blood smear, and HIV serology (Table 2). During the physical exam, place special attention on evaluating blood pressure, the abdomen, and the skin to help pinpoint the correct cause of the thrombocytopenia.

    Gestational thrombocytopenia

    First defined in 1986, gestational thrombocytopenia is now recognized as the most common cause of thrombocytopenia in pregnancy, accounting for 74% of cases.5 The second chief cause is preeclampsia/HELLP (hemolysis/elevated liver enzymes/low platelets) syndrome, comprising 21% of cases, followed by idiopathic thrombocytopenic purpura (ITP) which accounts for just 5% of thrombocytopenic patients.1

    Typically, gestational thrombocytopenia is identified on a routine prenatal complete blood count screen. The patients are usually asymptomatic and have mild thrombocytopenia (platelet counts usually above 70,000/μL). Researchers have reported that 97% of thrombocytopenic pregnant women with platelet counts above 115,000 had gestational thrombocytopenia, whereas only 47% of those with platelet counts less than 75,000 had this diagnosis.6

    With gestational thrombocytopenia, there are no associated signs or medical complications such as petechiae or bleeding. Preeclampsia and HELLP syndrome should be ruled out, however. Unfortunately, though, further laboratory evaluation for antiplatelet antibodies cannot separate gestational thrombocytopenia from ITP or HELLP syndrome.

    Two things confirm the diagnosis of gestational thrombocytopenia:

    (1) the incidental finding of thrombocytopenia on CBC in an asymptomatic pregnant patient with no significant past coagulopathy, and

    (2) resolution of the platelet count to normal in the postpartum period.

    Once you rule out preeclampsia in an otherwise healthy parturient, platelet counts above 100,000/μL require no further evaluation.

    On the other hand, if the platelet count falls below 70,000/μL, seek other causes and follow complete blood counts until you deem the platelet count stable.7 Although pregnant women with gestational thrombocytopenia can have antiplatelet antibodies, thrombocytopenia poses little-to-no risk of neonatal morbidity8-10 and no increased risk of maternal hemorrhage. Therefore, provide routine prenatal care to women with gestational thrombocytopenia. And keep in mind that this benign condition has been reported to recur in subsequent pregnancies.11

    Eliza M.F. Berkley, MD
    DR. BERKLEY is Assistant Professor, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Eastern Virginia ...
    Sarah J. Kilpatrick, MD, PhD
    Dr. Kilpatrick is the Helping Hand Endowed Chair in the Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center, Los ...


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