A 33-year-old woman, gravida 2 para 1, comes to the clinic for a routine prenatal visit at 26 weeks gestation. Her pregnancy has been uncomplicated. The patient's BMI was 23 kg/m² at her initial prenatal visit, and her laboratory results were as follows: An ultrasound at 20 weeks gestation showed an anterior placenta and normal fetal anatomy. The patient's only concern today is lower leg swelling that occurs after prolonged standing but resolves with sitting or lying down. Her last pregnancy was complicated by Group B Streptococcus colonization requiring prophylaxis during delivery. The patient has no chronic medical problems and takes only prenatal vitamins. She is a radiologist and does not use tobacco, alcohol, or drugs. Blood pressure is 135/80 mm Hg and pulse is 65/min. Physical examination shows minimal pedal edema and negative Homan sign bilaterally. Fundal height is 27 cm and fetal heart rate is 140/min. Which of the following tests should be obtained at this visit?

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During the second and third trimesters of pregnancy, the placenta secretes hormones that increase maternal insulin resistance to promote fetal growth and metabolism. Women with inadequate pancreatic function to overcome insulin resistance are at risk of developing gestational diabetes mellitus (GDM). Risk factors for GDM include obesity, excessive weight gain during pregnancy, family history of DM, and a previous macrosomic infant. Uncontrolled hyperglycemia is dangerous to both the mother and fetus, with complications such as miscarriage, birth defects, fetal macrosomia, and preeclampsia. Women who are at risk for undiagnosed type 2 DM should undergo screening during their initial prenatal visit with a hemoglobin A1c or glucose tolerance test. All other patients should undergo an oral glucose challenge test (GCT) at the end of the second trimester (24-28 weeks). The most common approach consists of screening with a 1-hour 50-g GCT, followed by confirmation with a 3-hour 100-g glucose tolerance test. (Choice A) A 24-hour urine protein collection is the gold standard for diagnosis of proteinuria associated with preeclampsia. It should be ordered in a patient with hypertension. Although increased edema can be a sign of preeclampsia, it is also seen in normal pregnancy. (Choices B and E) Hepatitis B surface antigen and Chlamydia trachomatis testing is done at the initial prenatal visit and repeated during the third trimester in high-risk patients (eg, intravenous drug use, sexually transmitted infection earlier in pregnancy). (Choice C) A urine culture is obtained at the initial prenatal visit or if the patient has cystitis symptoms. Asymptomatic bacteriuria is treated during pregnancy due to increased risk of ascending infection (eg, pyelonephritis). This patient is asymptomatic and had a negative urine culture; therefore, a repeat urine culture is not indicated. (Choice D) Group B Streptococcus (GBS) testing is performed at 35-37 weeks gestation. Positive testing requires intrapartum prophylaxis to prevent neonatal sepsis. Patients with GBS colonization in a prior pregnancy do not require earlier screening or treatment. Educational objective: During the second and third trimesters, placental hormones create increased maternal insulin resistance and can result in pathologic maternal hyperglycemia. All women at 24-28 weeks gestation should undergo routine screening for gestational diabetes mellitus. References: Practice bulletin no. 137: gestational diabetes mellitus. (http://www.ncbi.nlm.nih.gov/pubmed/23969827)

A 33-Year-Old Woman, Gravida 2 Para 1, Comes to the Clinic