What is the appropriate evaluation and management of anemia in a patient at 26 weeks gestation?

Evaluation and Management of Anemia at 26 Weeks Gestation

At 26 weeks gestation, screen for anemia with a complete blood count, and if hemoglobin is <10.5 g/dL, initiate therapeutic oral iron at 60-120 mg elemental iron daily while investigating the underlying cause. 1, 2

Initial Diagnostic Evaluation

Screening and Classification

• Obtain a complete blood count (CBC) with indices to establish the diagnosis, as anemia at 26 weeks is defined as hemoglobin <10.5 g/dL 1, 2
• Classify severity: mild (10.0-10.4 g/dL), moderate (7.0-9.9 g/dL), or severe (<7.0 g/dL) 1
• Order additional laboratory tests including mean corpuscular volume (MCV), red cell distribution width (RDW), serum ferritin, reticulocyte count, and peripheral blood smear 3, 1

Critical Diagnostic Considerations

• Check blood type and antibody screen to evaluate for alloimmunization, which is a common cause of both maternal and fetal anemia 3
• Perform Kleihauer-Betke test if fetomaternal hemorrhage is suspected 3
• Consider parvovirus B19 serology if clinically indicated, as parvovirus is the most common infectious cause of fetal anemia with a 6% fetal death risk after 20 weeks 4, 5

Management Based on Severity

Mild Anemia (Hemoglobin 10.0-10.4 g/dL)

• Initiate therapeutic oral iron at 60-120 mg elemental iron daily if MCV is low or normal, as this represents likely iron deficiency 1, 2
• Intermittent dosing (every other day) is as effective as daily dosing with fewer gastrointestinal side effects 1
• Recheck hemoglobin in 4 weeks, expecting an increase of at least 1 g/dL if iron deficiency is the cause 1
• If no response after 4 weeks, perform further evaluation with serum ferritin and consider alternative diagnoses 1
• Once hemoglobin normalizes for gestational age, decrease to maintenance dose of 30 mg/day 1

Moderate Anemia (Hemoglobin 7.0-9.9 g/dL)

• Requires further investigation beyond presumptive iron deficiency, including hemoglobin electrophoresis if patient is of African, Mediterranean, or Southeast Asian ancestry to rule out thalassemia 1, 2
• Continue therapeutic oral iron 60-120 mg daily while awaiting results 1
• Consider referral to hematology for evaluation of underlying causes 1
• If oral iron is not tolerated or absorption is impaired, intravenous iron is highly effective and should be considered 3

Severe Anemia (Hemoglobin <7.0 g/dL)

• Transfuse 2-3 units of packed red blood cells urgently, as this is a medical emergency requiring immediate intervention regardless of symptoms 3
• Each unit raises hemoglobin by approximately 1.5 g/dL 3, 1
• Perform transfusion in a location with immediate access to operating room capabilities given the viable gestational age 1
• Establish IV access and prepare for potential emergency delivery if fetal distress develops 1
• Initiate oral iron 60-120 mg daily immediately after transfusion to replenish stores and prevent recurrence 3, 1
• Recheck hemoglobin within 1-2 weeks post-transfusion to ensure adequate response 3, 1

Concurrent Fetal Assessment

Screening for Fetal Anemia

• Evaluate the fetus using middle cerebral artery peak systolic velocity (MCA-PSV) Doppler, as maternal anemia may indicate an underlying condition affecting the fetus 3, 5
• MCA-PSV should be measured close to the vessel's origin at a zero-degree angle without angle correction 3
• If MCA-PSV exceeds 1.5 multiples of the median, this indicates moderate to severe fetal anemia and requires referral to a center with expertise in intrauterine transfusion 3, 5
• At 26 weeks gestation, normal fetal hemoglobin is approximately 12.6 g/dL (median), with severe fetal anemia defined as <6.9 g/dL 5

Fetal Monitoring During Maternal Stabilization

• Continuous fetal heart rate monitoring throughout any transfusion procedure is essential 1
• If hydrops fetalis is present, immediate referral for intrauterine transfusion is indicated 3

Ongoing Management and Follow-Up

Serial Monitoring

• Recheck hemoglobin every 1-2 weeks throughout the remainder of pregnancy after initial treatment 3
• Continue therapeutic iron supplementation throughout pregnancy 1
• Provide nutritional counseling regarding iron-rich foods (red meat, dark leafy greens, fortified cereals) and absorption enhancers (vitamin C) 1

Delivery Planning

• Continue pregnancy with close surveillance unless maternal instability or fetal compromise necessitates delivery, as risks of prematurity at 26 weeks generally outweigh risks of continuing pregnancy after maternal stabilization 3
• If fetal anemia is confirmed and severe, coordinate with maternal-fetal medicine for possible intrauterine transfusion 3
• Plan delivery at 37-38 weeks if fetal anemia is identified, or earlier if maternal or fetal indications develop 4, 3

Critical Pitfalls to Avoid

• Do not delay transfusion for diagnostic workup when hemoglobin is <7.0 g/dL, as this is a medical emergency 3
• Do not assume severe anemia is simple iron deficiency—investigate for acute blood loss, hemolysis, or bone marrow pathology 3
• Do not overlook fetal assessment, as maternal severe anemia may reflect conditions that also affect the fetus such as alloimmunization or parvovirus infection 3, 5
• Do not transfuse only one unit of packed red blood cells in severe anemia—2-3 units are necessary for adequate correction 3
• Be aware that very high hemoglobin (>15.0 g/dL) or hematocrit (>45.0%) at 26 weeks indicates poor blood volume expansion and is associated with hypertension, fetal growth retardation, and preterm delivery 4