An otherwise healthy 25-year-old woman, gravida 1, para 0, is evaluated in the clinic at 3… — USMLE Step 2 CK

An otherwise healthy $25$ -year-old woman, gravida $1$ , para $0$ , is evaluated in the clinic at $30$ weeks gestation for a scheduled prenatal check-up. She mentions noticing puffiness around her ankles by the end of the day, which generally resolves after a night's sleep. She denies headaches, blurred vision, or abdominal pain. Vital signs show a temperature of $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure of $112/68\text{ mm Hg}$ , heart rate of $86/\text{min}$ , and respiratory rate of $16/\text{min}$ . Physical examination reveals trace, bilateral dependent edema of the lower extremities but is otherwise unremarkable. A urine dipstick shows no protein or glucose.

The patient is highly anxious regarding laboratory results from her previous visit at $28$ weeks gestation, which she reviewed online. The results are as follows:

Hemoglobin: $11.5\text{ g/dL}$
Leukocyte count: $14,200/\text{mm}^3$
Platelet count: $220,000/\text{mm}^3$
Serum creatinine: $0.5\text{ mg/dL}$

Based on the clinical presentation and laboratory findings, which of the following is the most appropriate next step in management?

A
Order a 24-hour urine collection to quantify total protein excretion
B
Perform a renal ultrasound to evaluate for structural abnormalities
Explain that her findings are expected in pregnancy and no further testing is requiredAnswer
D
Prescribe oral antibiotics for a suspected subclinical infection
E
Administer oral furosemide to manage the lower extremity edema

Answer

Explain that her findings are expected in pregnancy and no further testing is required

The correct action is to explain that her findings are expected in pregnancy and no further testing is required. Pregnancy induces significant maternal physiologic adaptations across multiple organ systems. Blood volume expands (with plasma volume increasing proportionally more than red blood cell mass), leading to a dilutional decrease in hemoglobin concentration; however, a hemoglobin level

\geq 11.0\text{ g/dL}

in the first and third trimesters, or

\geq 10.5\text{ g/dL}

in the second trimester, is considered normal. Mild leukocytosis (typically up to

15,000/\text{mm}^3

during pregnancy and even higher during labor) is a normal physiologic stress response. Renal blood flow and glomerular filtration rate (GFR) increase by approximately 50%, which leads to increased clearance of creatinine and a consequently lower normal range for serum creatinine (

0.4-0.8\text{ mg/dL}

) compared to the nonpregnant state. Furthermore, dependent lower extremity edema is a classic, expected finding late in pregnancy due to sodium retention and mechanical compression of the inferior vena cava by the gravid uterus. Because this patient is asymptomatic (no signs of infection) and has normal blood pressure with a negative urine dipstick, all her clinical and laboratory findings are purely physiologic. The most appropriate management is reassurance.

Step-by-Step Solution

Evaluate the patient's clinical symptoms and vital signs.

The patient has mild dependent edema, strictly normal blood pressure, and no signs of severe preeclampsia.

To rule out hypertensive disorders of pregnancy, which would require urgent intervention.

Interpret the laboratory findings in the context of normal pregnancy adaptations.

Hemoglobin of

11.5\text{ g/dL}

, leukocyte count of

14,200/\text{mm}^3

, and creatinine of

0.5\text{ mg/dL}

are all well within normal limits for the third trimester.

Normal reference ranges shift significantly during pregnancy due to systemic physiologic changes.

Determine the appropriate management plan based on the findings.

Reassurance and routine prenatal care are indicated.

Because all findings are physiologic, medical interventions or further diagnostic workups are unnecessary.

Key Concept

Normal maternal physiologic adaptations to pregnancy include mild dilutional anemia, baseline leukocytosis, decreased serum creatinine (due to increased GFR), and dependent lower extremity edema.

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