Treatment of Anemia in Pregnancy
For pregnant women with anemia, prescribe oral iron supplementation at 60-120 mg of elemental iron daily, which remains the first-line treatment despite insufficient evidence linking it to improved clinical outcomes. 1, 2
Screening and Diagnosis
Screen all pregnant women at booking and again at 28 weeks using a complete blood count (CBC) or hemoglobin/hematocrit measurement where CBC is unavailable. 3
Diagnose anemia when hemoglobin is <11 g/dL in any trimester, recognizing that physiologic hemodilution during pregnancy makes precise diagnosis challenging. 3, 4
Understand that serum hemoglobin or hematocrit alone has unknown sensitivity and specificity for detecting iron deficiency anemia in pregnancy due to normal physiologic hemodilution. 4
Note that serum ferritin has limited utility during pregnancy because levels decrease in late pregnancy despite adequate bone marrow iron stores, and it increases during inflammation as an acute phase reactant. 4
Treatment Algorithm by Severity
Mild to Moderate Anemia (Hemoglobin 7.0-10.9 g/dL)
Prescribe 60-120 mg of elemental iron daily as oral supplementation, which improves hemoglobin and ferritin levels even though evidence for clinical benefit on maternal or infant outcomes remains insufficient. 1, 4
Provide dietary counseling emphasizing iron-rich foods (meat, poultry, certain fruits and vegetables) and factors enhancing absorption, noting that fortified grain products provide over 50% of iron in the U.S. food supply. 1, 4
Reassess hemoglobin after 4 weeks, expecting an increase of ≥1 g/dL in hemoglobin or ≥3% in hematocrit to confirm adequate response. 1, 2
Continue iron supplementation for 2-3 months after hemoglobin normalizes to replenish iron stores, as stopping treatment prematurely is a common pitfall. 2
Severe Anemia with Presyncope
Hospitalize immediately and assess hemodynamic stability by checking vital signs, orthostatic blood pressure changes, and signs of ongoing bleeding, as presyncope indicates significant cardiovascular compromise. 1
Rule out acute hemorrhage, particularly placental complications in second and third trimesters that can cause rapid blood loss. 1
Initiate the same oral iron regimen (60-120 mg daily) once stabilized, keeping the patient hospitalized until hemodynamically stable with improving hemoglobin trends. 1
Special Populations and Considerations
High-Risk Groups
Non-Hispanic Black and Mexican American women have higher prevalence rates of iron deficiency than white women. 4
Women with vegetarian diets may require nearly double the iron supplementation (up to 240 mg daily) because non-heme iron from plant sources is less well-absorbed than heme iron from meat. 1, 4
Risk factors include: diets lacking iron-rich foods, gastrointestinal disease, medications decreasing iron absorption (antacids), short interpregnancy intervals, and parity ≥2. 4
When to Escalate Evaluation
If anemia persists after 4 weeks of compliant oral iron therapy, order additional laboratory tests including MCV, RDW, and serum ferritin, and consider hemoglobinopathies particularly in women of African, Mediterranean, or Southeast Asian ancestry. 2
Investigate for underlying bleeding sources if anemia is disproportionate to gestational age or if there is vaginal bleeding history. 1
Alternative Routes of Administration
Intravenous and intramuscular iron produce better hematological indices than oral iron but lack evidence on clinical outcomes and carry concerns about adverse effects including venous thrombosis, severe allergic reactions (IV), and pain with discoloration (IM). 5, 4
Reserve parenteral iron for cases of oral iron intolerance or failure, recognizing the evidence gap regarding safety in pregnancy. 5
Adverse Effects and Monitoring
Common oral iron side effects are self-limited and transient: nausea, constipation, diarrhea, darkening of urine/stool, and teeth/gum staining. 4
A dose-response relationship exists between iron dose and gastrointestinal adverse effects, suggesting lower doses within the 60-120 mg range may improve compliance. 4, 5
Drug interactions occur with phenytoin (folic acid antagonizes anticonvulsant action), antacids (decrease iron absorption), and antibiotics like tetracycline (cause false-low folate levels). 6
Folic Acid Supplementation
Folic acid is indicated for megaloblastic anemias of pregnancy and requirements are markedly increased during pregnancy. 6
Do not give folic acid in doses >0.4 mg daily until pernicious anemia is ruled out, as it may mask hematologic manifestations while neurologic damage progresses. 6
Critical Evidence Gaps
The USPSTF assigns an "I" statement (insufficient evidence) for both screening and routine iron supplementation because:
No studies directly evaluate screening effectiveness on maternal or infant health outcomes in asymptomatic pregnant women. 4
No studies assess whether change in iron status from treatment or supplementation improves clinical outcomes, representing a critical evidence gap. 4
Iron supplementation improves intermediate hematologic indices but has inadequate evidence for effects on maternal anemia, cesarean delivery, preterm delivery, infant mortality, or low birth weight. 4
Despite these evidence limitations, oral iron supplementation at 60-120 mg daily remains standard practice given its safety profile, low cost, and biological plausibility for benefit, particularly in populations at higher risk for iron deficiency. 1, 2