What is the approach to a pregnant patient with elevated Erythrocyte Sedimentation Rate (ESR)?

Approach to Elevated ESR in Pregnancy

An elevated ESR in pregnancy is most commonly a normal physiological finding and should not trigger extensive workup in an asymptomatic patient, as ESR values up to 75 mm/hr occur in 82.7% of normal pregnant women at term. 1

Understanding Normal ESR Changes in Pregnancy

Pregnancy physiologically elevates ESR through multiple mechanisms:

• Normal pregnancy induces elevated erythrocyte sedimentation rates as a benign finding, with mean ESR of 55.7 mm/hr at term and 50% of pregnant women having ESR ≥50 mm/hr 2
• The American College of Rheumatology explicitly recognizes that "elevated erythrocyte sedimentation" is among normal pregnancy symptoms that "may falsely mimic symptoms of active RMD" 1
• ESR correlates significantly with iron status in pregnancy, including hemoglobin concentration, hematocrit, and serum iron parameters 2

Clinical Decision Algorithm

Step 1: Assess for Symptoms and Risk Factors

Do not pursue extensive workup if the patient is asymptomatic:

• ESR should not be used to screen asymptomatic persons for disease 3
• If an increased ESR is encountered without immediate explanation, repeat the test in several months rather than pursue exhaustive evaluation 3

Identify specific high-risk scenarios requiring investigation:

• Known rheumatic and musculoskeletal disease (RMD) such as SLE, requiring differentiation between disease flare versus normal pregnancy changes 1
• Symptoms suggesting infection, particularly in orthopedic, pediatric, or gynecologic settings 3
• Clinical features of temporal arteritis or polymyalgia rheumatica 3
• Pregnancy-induced hypertension syndromes (preeclampsia) that may mimic lupus nephritis, scleroderma renal crisis, or vasculitis flare 1

Step 2: Determine if ESR Exceeds Critical Threshold

ESR >100 mm/hr warrants targeted investigation:

• Values exceeding 100 mm/hr have 90% predictive value for serious underlying disease, most often infection, collagen vascular disease, or metastatic tumor 3
• In this scenario, perform minimal but focused testing to identify the cause rather than comprehensive screening 3

Step 3: Evaluate for Anemia and Iron Deficiency

Check hemoglobin and iron studies if ESR is elevated:

• The difference in mean ESR between anemic and non-anemic pregnant women is highly significant (p<0.001) 2
• ESR may be useful in assessing iron deficiency in anemia of chronic disease when correlated with serum ferritin level 3
• 87.5% of anemic pregnant women with serum ferritin >50 μg/L had ESR ≥50 mm/hr, suggesting possible chronic infection raising ferritin levels 2

Step 4: Distinguish Pregnancy Changes from Disease Flare in RMD Patients

For patients with known rheumatic disease, coordinate with rheumatology and maternal-fetal medicine:

• Pregnancy-induced hypertension syndromes (preeclampsia) may be confused with lupus nephritis, scleroderma renal crisis, or vasculitis flare 1
• HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) or eclampsia may resemble severe disease flare 1
• Distinguishing among these syndromes requires expertise of rheumatologists and obstetrics-gynecology or maternal-fetal medicine physicians working together 1
• Normal pregnancy symptoms including malar erythema, chloasma gravidarum, anemia, elevated ESR, and diffuse arthralgias may falsely mimic active RMD 1

Common Pitfalls to Avoid

Do not order ESR as routine screening in asymptomatic pregnant patients:

• Any test becomes expensive when ordered often, and evaluation of false-positive results may incur substantial costs and place the patient at risk from additional procedures 3

Do not assume elevated ESR automatically indicates pathology:

• ESR lacks sensitivity and specificity, and physiologic elevation is the norm in pregnancy 3, 2

Do not pursue exhaustive workup for mildly elevated ESR (<100 mm/hr) in asymptomatic patients:

• Repeat testing in several months is more appropriate than immediate extensive investigation 3

Do not overlook iron deficiency as a contributor:

• Check complete blood count and iron studies before attributing elevated ESR to other causes 2