A 28-year-old woman, G1P0 at 30 weeks gestation, comes to the clinic for a routine prenata… — USMLE Step 2 CK

A 28-year-old woman, G1P0 at $30$ weeks gestation, comes to the clinic for a routine prenatal follow-up. She has a 5-year history of systemic lupus erythematosus (SLE) that has been quiescent on hydroxychloroquine. She reports mild, generalized fatigue and occasionally feeling "out of breath" when climbing stairs, but she explicitly denies joint pain, facial rashes, fevers, or chest pain. Her blood pressure is $112/70 \text{ mm Hg}$ , and her pulse is $85/\text{min}$ . Physical examination shows trace bilateral pedal edema but is otherwise unremarkable. Fetal heart tones are $145/\text{min}$ .

Laboratory studies show the following:

Test	Result
Hemoglobin	$10.2 \text{ g/dL}$
Leukocyte count	$11,500/\text{mm}^3$
Platelet count	$180,000/\text{mm}^3$
Serum creatinine	$0.6 \text{ mg/dL}$
Anti-dsDNA antibodies	Negative
Complement C3 and C4	Normal

Arterial blood gas analysis on room air reveals:

Parameter	Result
pH	$7.44$
PaCO $_2$	$28 \text{ mm Hg}$
HCO $_3^-$	$19 \text{ mEq/L}$

Urinalysis shows trace protein with no red blood cells or cellular casts. The patient is anxious and asks if her recent symptoms and laboratory abnormalities indicate that her autoimmune disease is worsening. Which of the following is the most appropriate next step in management?

Continuation of current management and reassuranceAnswer
B
Initiation of high-dose oral prednisone therapy
C
Administration of oral sodium bicarbonate
D
Initiation of oral furosemide therapy
E
Initiation of empiric broad-spectrum antibiotic therapy

Answer

Continuation of current management and reassurance

The correct approach is to continue current management and provide reassurance. This patient's symptoms (mild fatigue, occasional dyspnea) and laboratory findings (hemoglobin of

10.2 \text{ g/dL}

, leukocyte count of

11,500/\text{mm}^3

, and a compensated respiratory alkalosis) are hallmark, normal physiologic adaptations to pregnancy. Her systemic lupus erythematosus (SLE) remains clinically and serologically inactive, as strongly evidenced by her normal complement levels, negative anti-dsDNA antibodies, and the absence of active urinary sediment (e.g., no red blood cell casts or significant proteinuria). Hydroxychloroquine is safe during pregnancy and is highly recommended to maintain disease remission and improve fetal outcomes.

Step-by-Step Solution

Evaluate the clinical presentation and laboratory findings in the context of the third trimester of pregnancy.

The patient exhibits mild fatigue, trace pedal edema, dilutional anemia (hemoglobin

10.2 \text{ g/dL}

), mild leukocytosis (

11,500/\text{mm}^3

), and a fully compensated respiratory alkalosis.

Pregnancy induces profound physiologic adaptations, including expanded plasma volume (causing dilutional anemia), progesterone-driven hyperventilation (causing chronic respiratory alkalosis with a compensatory drop in bicarbonate), and benign leukocytosis.

Assess the status of the patient's systemic lupus erythematosus (SLE) to rule out an acute disease flare.

The SLE is clinically and serologically quiescent. There are no active systemic symptoms, complement levels are normal, anti-dsDNA is negative, and the urinalysis is bland.

An active SLE flare in pregnancy would typically present with worsening proteinuria, hypertension, falling C3/C4 complement levels, and rising anti-dsDNA titers, none of which are present.

Determine the most appropriate management based on the findings.

The patient requires reassurance and continuation of her current hydroxychloroquine regimen.

Since all findings point to a normal, healthy pregnancy and well-controlled SLE, no acute interventions (such as steroids or diuretics) are indicated. Hydroxychloroquine should be maintained to prevent future flares.

Key Concept

Differentiating normal physiologic adaptations of pregnancy from acute systemic lupus erythematosus (SLE) flares

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