Thrombocytopenia, generally defined as a platelet count below 150 × 109/L, is the most common hematologic disorder in pregnancy after anemia. It develops in roughly 5% to 10% of all pregnancies and can result from a range of conditions that may or may not be unique to pregnancy. Making a differential diagnosis can be difficult, as pregnancy itself is associated with various metabolic, immunologic, and homeostatic changes that need to be considered when attempting to find the cause of thrombocytopenia in a patient. Management can also be complex because of the potential adverse effects of treatment on the patient and the fetus.

Overall, thrombocytopenia in pregnancy presents major challenges to clinicians, including the need to identify whether thrombocytopenia is associated with a life-threatening disorder and to evaluate the risk of fetal thrombocytopenia, which can lead to abnormal bleeding in the newborn, sometimes even before birth. Although most cases of thrombocytopenia in pregnancy tend to be mild without any adverse outcome for the mother or baby, a low platelet count could indicate the presence of a serious disorder that carries significant morbidity. A general approach to the diagnosis and management of thrombocytopenia in pregnancy was discussed in a paper published in Blood Reviews.

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“The key points are [that] thrombocytopenia can occur commonly during pregnancy, and it is important to determine the etiology as this has implications for the health of the mother and fetus,” said Allyson Pishko, MD, of the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, in an interview with Hematology Advisor. “Features such as the severity of thrombocytopenia and trimester of onset can provide key clues.”

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Gestational thrombocytopenia is the most common cause of thrombocytopenia during pregnancy and is defined as a mild thrombocytopenia that occurs during the third trimester and spontaneously resolves postpartum with generally no risk of neonatal thrombocytopenia. A low platelet count can also be associated with other disorders such as preeclampsia; hemolysis, elevated liver enzymes, low platelets [HELLP] syndrome; or idiopathic thrombocytopenic purpura (ITP).

Other causes of thrombocytopenia tend to be quite rare but include disseminated intravascular coagulation (DIC), thrombotic thrombocytopenic purpura and hemolytic-uremic syndrome (TTP-HUS), congenital platelet disorders, bone marrow disease, and hypersplenism.

Diagnosis is made based on clinical assessment, medical history of current or previous bleeding problems, or transfusion history, as well as findings upon examination. “Symptoms that should alert providers [include] excessive bruising or bruising in atypical locations,” said Dr Pishko. “Gum bleeding and frequent nose bleeds can also be symptoms. With hypertension or kidney problems, the provider should also look for thrombocytopenia, as this may indicate severe preeclampsia or other serious conditions.”

The trimester of pregnancy can provide an important clue as to the etiology of thrombocytopenia. For example, a gradual decrease in platelet count occuring in the middle of the second trimester is suggestive of gestational thrombocytopenia. However, declining counts earlier in the pregnancy suggest the etiology is something other than gestational thrombocytopenia, as does the presence of severe thrombocytopenia.