A 27-year-old woman, gravida 1 para 0, at 28 weeks gestation comes to the office for a routine prenatal visit. Her initial prenatal laboratory results at 12 weeks gestation were as follows: The patient reports no vaginal bleeding, leakage of fluid, or contractions. There is good fetal movement. She has increasing urinary frequency and nocturia but no dysuria or hematuria. The patient has a history of tension headaches, which have become more frequent but resolve with acetaminophen. She has no other chronic medical conditions or previous surgeries. The patient works in a retirement home and reports leg swelling at the end of her shift. She is a vegetarian and takes a daily prenatal vitamin. She does not use tobacco, alcohol, or illicit drugs. Temperature is 37 C (98.6 F), blood pressure is 128/76 mm Hg, and pulse is 86/min. BMI is 30 kg/m²; the patient has been gaining 0.5 kg (1.1 lb) a week during the pregnancy. The fetal heart rate is 152/min. Examination shows a uterus consistent with a 28-week gestation. There is trace lower extremity edema bilaterally. The patient has had no laboratory evaluations since her initial prenatal visit. The patient's test results from the 28-week prenatal visit are as follows: Which of the following is the most likely diagnosis?

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Explanation: 11ec2b69_c03c_9909_8f63_5bfd1c71f1d2_MD0005_00 Gestational thrombocytopenia is a common cause of thrombocytopenia in pregnancy and is a benign, asymptomatic condition defined by a platelet count of 70,000-150,000/mm³. Gestational thrombocytopenia develops in the second or third trimester of pregnancy in patients with no prior history of thrombocytopenia or associated fetal thrombocytopenia and resolves after delivery. The etiology is not well understood but may be a combination of hemodilution and accelerated destruction of platelets. However, the risk of fetal and maternal hemorrhage is not increased. Management is conservative and includes serial complete blood counts, with frequency depending on severity. The patient should be evaluated postpartum to ensure resolution. (Choice B) Preeclampsia with severe features can present with thrombocytopenia. However, patients typically also have hypertension (blood pressure >140/90 mm Hg) or signs/symptoms of end-organ damage (eg, right upper quadrant pain, scotoma). Although this patient has headaches, they are chronic and mild, and resolve with analgesics. In contrast, headaches associated with preeclampsia are acute, severe, and often unresponsive to analgesics. (Choice C) Thrombotic thrombocytopenic purpura is associated with thrombocytopenia (often with purpura but rarely with severe bleeding), microangiopathic hemolytic anemia, acute renal insufficiency, neurologic abnormalities, and fever. This patient is asymptomatic and was diagnosed incidentally with routine prenatal screening, making this serious diagnosis unlikely. (Choice D) Vitamin B₁₂ deficiency can present as pancytopenia; however, the associated anemia is macrocytic (mean corpuscular volume >100 fL), not normocytic, as in this patient. In addition, this patient does not have the neurologic symptoms typically associated with vitamin B₁₂ deficiency (eg, dementia, paresthesias). ₁₂ ₁₂ (Choice E) Patients with type 2B von Willebrand disease can exhibit mild thrombocytopenia, although more commonly they have normal platelet levels. These patients typically have signs of platelet dysfunction (eg, easy bruising, joint bleeding) rather than an asymptomatic presentation. Educational objective: Gestational thrombocytopenia is a benign condition defined by mild, asymptomatic thrombocytopenia that develops during pregnancy. Patients have no history of chronic thrombocytopenia, no evidence of fetal thrombocytopenia, and spontaneous resolution after delivery. References: Practice bulletin no. 166: thrombocytopenia in pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/27548554) Thrombocytopenic syndromes in pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/27512485)

A 27-Year-Old Woman, Gravida 1 Para 0, at 28 Weeks