Anemia in Pregnancy

Diagnosis and Classification

• Anemia in pregnant women is defined as a hemoglobin concentration below the 5th percentile of the distribution of hemoglobin concentration in a healthy reference population, correctly identifying 37% of women of childbearing age who were iron deficient and correctly classifying 93% of women as not having iron deficiency, according to the Centers for Disease Control and Prevention (CDC) 1
• The American College of Obstetricians and Gynecologists defines anemia in pregnancy as hemoglobin <11.0 g/dL in the first trimester and <10.5 g/dL in the second and third trimesters, with a prevalence that increases throughout pregnancy, ranging from 1.8% in the first trimester to 27.4% in the third trimester, as reported by the Annals of Internal Medicine 2
• A ferritin level below 30 ng/mL is diagnostic of iron deficiency, and a level of 8 in the third trimester clearly indicates iron deficiency anemia, requiring prompt treatment to prevent adverse maternal and fetal outcomes 1

Physiological Changes in Pregnancy

• During the first and second trimesters, hemoglobin concentration and hematocrit decline due to expanding blood volume, while in women with adequate iron intake, hemoglobin concentration gradually rises during the third trimester toward pre-pregnancy levels 1
• In women who do not take iron supplements, hemoglobin concentration remains low in the third trimester 1
• Hemoglobin cutoffs should be adjusted for altitude, smoking status, and race, as recommended by the CDC 1

Risk Factors and Causes

• Women of Mediterranean, African, or Southeast Asian ancestry are at increased risk of thalassemia, a cause of anemia in pregnancy, according to the CDC 1
• Sickle cell disease or trait is also a cause of anemia in pregnancy, particularly in women of certain ethnic backgrounds, as reported by the CDC 1
• Poor nutrition or diets low in iron, multiple pregnancies, closely spaced pregnancies, adolescent pregnancy, high-altitude residence, and smoking are risk factors for anemia in pregnancy, as noted by the CDC 1

Screening and Prevention

• The CDC recommends routine screening for anemia at the first prenatal visit and at 24-28 weeks gestation, as well as prophylactic low-dose iron supplementation (30 mg/day) starting at the first prenatal visit 1
• Patients should be advised to consume iron-rich foods, such as red meat, poultry, fish, beans, lentils, tofu, dark leafy greens, and iron-fortified cereals and breads, and to avoid calcium supplements, tea, coffee, and dairy products within 2 hours of iron supplements as they inhibit absorption 1
• The CDC recommends counseling patients to consume vitamin C-rich foods with meals to enhance absorption 1

Treatment and Management

• Assessment of the severity of anemia is necessary to determine the appropriate treatment, with mild (Hb 10-10.5 g/dL) cases treated with oral iron supplementation, moderate (Hb 7-9.9 g/dL) cases considered for IV iron, and severe (Hb <7 g/dL) cases considered for blood transfusion, as recommended by the American College of Obstetricians and Gynecologists 3, 4, 5
• The following table summarizes the indications for blood transfusion in pregnant women with IDA:

• Severe anemia (Hb <7 g/dL) and hemodynamic instability are primary indications for blood transfusion in pregnant women with IDA, according to the American College of Obstetricians and Gynecologists 4, 5
• Post-transfusion IV iron supplementation is necessary to replenish iron stores, and monitoring of hemoglobin and iron parameters (ferritin) 2-4 weeks after transfusion is recommended, with continuation of iron supplementation until iron stores are replenished (ferritin >30 μg/L) 5
• Repeat complete blood count in 4 weeks to assess response to therapy, as recommended by the CDC 1
• Iron supplementation should continue postpartum, especially if anemia persists or blood loss during delivery was significant, to ensure adequate iron stores for breastfeeding and maternal recovery 1

Complications and Pitfalls

• Severe anemia (Hb <6 g/dL) is associated with an increased risk of preterm birth, low birth weight, small-for-gestational age infants, stillbirth, perinatal mortality, postpartum hemorrhage, and increased need for blood transfusion, as reported by the CDC 1
• Untreated iron deficiency anemia in the third trimester can lead to adverse maternal and fetal outcomes, including preterm delivery and low birth weight, making prompt treatment crucial 1
• Failure to distinguish between physiologic anemia of pregnancy and true iron deficiency, overlooking non-iron deficiency causes in non-responsive cases, and not adjusting hemoglobin cutoffs for altitude or smoking status are common pitfalls in management, according to the CDC 1
• Excessive iron supplementation should be avoided by monitoring response and adjusting dosage accordingly, with a maintenance dose of 30 mg/day after hemoglobin normalizes, as recommended by the CDC 1