An expectant mother at 25 weeks of gestation visits the obstetrician's office for a follow… — USMLE Step 2 CK

An expectant mother at $25$ weeks of gestation visits the obstetrician's office for a follow-up assessment. She is $27$ years old, gravida $1$ , para $0$ . Her pregnancy has been uncomplicated thus far. She reports experiencing occasional mild swelling in her ankles by the end of the day but denies headaches, visual changes, abdominal pain, contractions, or vaginal bleeding. Fetal movements are felt daily. Maternal vital signs show a blood pressure of $112/68$ mm Hg, heart rate of $82$ /min, and respiratory rate of $16$ /min. Fundal height is $25$ cm, and the fetal heart rate is $145$ /min. Laboratory studies obtained earlier this morning yield the following results:

Laboratory Test	Result
Hemoglobin	$10.7$ g/dL
Mean corpuscular volume	$92$ fL
Leukocytes	$13,800/\text{mm}^3$
Platelets	$135,000/\text{mm}^3$
Serum creatinine	$0.5$ mg/dL

Which of the following is the most appropriate next step in the management of this patient?

Continue with regular obstetric monitoring without additional diagnostic testingAnswer
B
Prescribe daily oral ferrous sulfate supplementation
C
Order a peripheral blood smear and coagulation profile
D
Obtain a urine culture and prescribe empiric antibiotics
E
Collect a 24-hour urine sample to measure total protein excretion

Answer

Continue with regular obstetric monitoring without additional diagnostic testing

The correct answer is to continue regular obstetric monitoring without additional diagnostic testing. This patient is experiencing expected physiological adaptations to pregnancy. In the second trimester, anemia is defined as a hemoglobin level strictly below

10.5

g/dL; therefore, her hemoglobin of

10.7

g/dL is normal dilutional anemia. Similarly, a leukocyte count up to

15,000/\text{mm}^3

is typical in healthy pregnancies. Her platelet count of

135,000/\text{mm}^3

indicates benign gestational thrombocytopenia (common and generally asymptomatic as long as it remains

>100,000/\text{mm}^3

). Furthermore, the increased glomerular filtration rate in pregnancy normally decreases serum creatinine levels (often to

0.4-0.8

mg/dL). Finally, dependent ankle edema without hypertension or proteinuria is a normal finding caused by the gravid uterus compressing pelvic veins. Since there is no pathology present, reassurance and routine monitoring are indicated.

Step-by-Step Solution

Evaluate the patient's clinical symptoms and vital signs.

The patient has mild dependent ankle edema with normal blood pressure and no worrisome symptoms (e.g., headache, visual changes).

To rule out hypertensive disorders of pregnancy, such as preeclampsia.

Interpret the hemoglobin level according to trimester-specific guidelines.

The hemoglobin is

10.7

g/dL, which is above the second-trimester threshold of

10.5

g/dL.

Plasma volume expands disproportionately to red blood cell mass during pregnancy, causing physiologic dilutional anemia. Trimester-specific cutoffs are required for an accurate diagnosis.

Assess the leukocyte, platelet, and creatinine values.

Leukocytes (

13,800/\text{mm}^3

) are within the normal pregnant range (up to

15,000/\text{mm}^3

). Platelets (

135,000/\text{mm}^3

) indicate benign gestational thrombocytopenia. Creatinine (

0.5

mg/dL) is appropriately decreased due to increased glomerular filtration rate.

To differentiate between normal maternal physiological adaptations and pathological states.

Determine the necessary management plan based on the assessment.

Since all clinical and laboratory findings are normal physiological variations of pregnancy, routine prenatal care should be continued.

Unnecessary diagnostic testing or medical therapy should be avoided in healthy, asymptomatic pregnant patients.

Key Concept

Normal physiologic adaptations to pregnancy include dilutional anemia, mild leukocytosis, gestational thrombocytopenia, and decreased serum creatinine.

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