A healthy 24-year-old woman, currently at 30 weeks gestation in her first pregnancy, prese… — USMLE Step 2 CK

A healthy 24-year-old woman, currently at 30 weeks gestation in her first pregnancy, presents for a standard obstetric check-up. She reports normal fetal movement and denies any headaches, visual changes, right upper quadrant abdominal pain, or dysuria. Her blood pressure is $114/72 \text{ mm Hg}$ , and her pulse is $82 \text{/min}$ . A routine basic metabolic panel is obtained and reveals a blood urea nitrogen (BUN) level of $7 \text{ mg/dL}$ and a serum creatinine of $0.4 \text{ mg/dL}$ . Urinalysis shows no proteinuria or hematuria. Which of the following is the most appropriate next step in management?

Continue routine prenatal careAnswer
B
Order a 24-hour urine protein collection
C
Schedule a renal and bladder ultrasound
D
Prescribe a high-protein dietary supplement
E
Repeat the basic metabolic panel in one week

Answer

Continue routine prenatal care

The correct answer is to continue routine prenatal care because the patient's laboratory values represent normal physiologic changes of pregnancy. During gestation, profound systemic vasodilation leads to an increase in renal plasma flow and a corresponding

40\%

50\%

increase in the glomerular filtration rate (GFR). This augmented filtration increases the clearance of urea and creatinine, leading to normally lower serum levels of BUN (typically

8-10 \text{ mg/dL}

) and creatinine (typically

0.4-0.8 \text{ mg/dL}

) compared to the non-pregnant state. Because this patient is completely asymptomatic, normotensive, and has expected laboratory changes, reassurance and routine care are appropriate.

Step-by-Step Solution

Analyze the patient's clinical presentation and vital signs.

The patient is asymptomatic with a normal blood pressure of

114/72 \text{ mm Hg}

To rule out hypertensive disorders of pregnancy, such as preeclampsia, which present with elevated blood pressure and end-organ damage.

Evaluate the laboratory findings.

BUN is

7 \text{ mg/dL}

and Creatinine is

0.4 \text{ mg/dL}

. Both values are lower than the standard non-pregnant reference ranges.

To determine if the renal function is normal or abnormal for a pregnant patient.

Apply knowledge of maternal physiologic adaptations to pregnancy.

Glomerular filtration rate (GFR) increases by 40-50% during pregnancy, leading to increased clearance and lower baseline serum levels of BUN and creatinine. The correct action is to recognize this as normal and continue standard care.

To distinguish between a pathological state and a normal, expected physiologic change.

Key Concept

During normal pregnancy, renal blood flow and glomerular filtration rate (GFR) increase by approximately 40-50%, resulting in decreased serum levels of blood urea nitrogen (BUN) and creatinine. These findings are normal physiologic changes and require only reassurance and routine care.

Estimated Time:1m 0s

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