A 24-year-old woman, gravida 1 para 0, at 28 weeks gestation comes to the office for a routine prenatal visit. She feels well and has had no vaginal bleeding, contractions, or leakage of fluid. Fetal movement is normal. The patient has no chronic medical conditions and her pregnancy has been uncomplicated. She previously had heavy menstrual periods that were managed with oral contraceptives. Blood pressure is 126/84 mm Hg and pulse is 78/min. Fundal height and fetal heart tones are normal. Today's third-trimester complete blood count is as follows: Coagulation studies and peripheral smear are within normal limits. The patient's first-trimester platelet count was 160,000/mm³. Urine dipstick today is negative for protein. Which of the following is the most likely cause of this patient's thrombocytopenia?

Question

Quizplus · Accepted Answer

This patient at 28 weeks gestation has mild, asymptomatic thrombocytopenia most consistent with gestational thrombocytopenia (GT), a benign, self-limited condition that can occur during pregnancy. GT is thought to arise due to the following: Plasma volume expansion: Maternal plasma volume expands approximately 30% during pregnancy to facilitate optimal fetal nutrient delivery and protect against maternal hemorrhage during delivery. Platelet production, however, does not typically increase during pregnancy; therefore, there is hemodilution and resultant thrombocytopenia. Sequestration/consumption of platelets in the placenta: The placenta is a highly vascular organ with similarities to the spleen, a major site of normal platelet sequestration. Platelets pool in the placental circulation and undergo accelerated consumption within the intervillous space, thereby reducing the serum platelet count. GT is commonly diagnosed in the third trimester, when plasma volume peaks; it is often an incidental finding on routine bloodwork. Patients with GT have mild thrombocytopenia (platelet count usually ≥100,000/mm³), no symptoms (eg, no bruising or bleeding), normal coagulation studies, and normal peripheral blood smear. (Choice A) Disseminated intravascular coagulation (DIC) is characterized by widespread activation of the coagulation cascade with thrombocytopenia due to platelet consumption. However, DIC is associated with bleeding and abnormal coagulation studies, which are not seen in this patient. (Choice B) Aspirin decreases the production of thromboxane A2 and inhibits platelet aggregation. Patients taking aspirin usually have normal or elevated platelet counts and decreased platelet clotting function. (Choice D) Immune complex-mediated complement activation occurs in inflammatory rheumatologic diseases (eg, systemic lupus erythematosus). Although these conditions are often associated with thrombocytopenia, patients typically have other symptoms. (Choice E) Thrombotic thrombocytopenic purpura (TTP) causes thrombocytopenia due to the formation of platelet clots in the microvasculature. However, TTP typically causes fever, microangiopathic hemolytic anemia, and neurologic abnormalities. Educational objective: Gestational thrombocytopenia is common in the third trimester and is typically mild, asymptomatic, and not associated with other laboratory abnormalities. It occurs due to hemodilution (ie, maternal plasma volume expansion) and increased sequestration/consumption of platelets in the placenta. __________ References: Thrombocytopenia in pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/29222249)

A 24-Year-Old Woman, Gravida 1 Para 0, at 28 Weeks