Classification and pathogenesis
In obstetric practice, two fundamentally different forms of red blood cell reduction are distinguished: true and physiological anemia.
The physiological form is not a disease. Its development is associated with a disproportionate increase in circulating plasma volume and red blood cell mass during pregnancy. Plasma expands faster, resulting in natural hemodilution (blood dilution) and a corresponding drop in hematocrit.
True anemia is represented in 90% of cases by iron deficiency anemia (IDA). Vitamin B12-deficiency and folate-deficiency forms are significantly less common in clinical practice.
Causes and risk factors of IDA
The main cause of IDA development is a sharp increase in the body's demand for exogenous iron. This is due to two parallel processes:
- Intensification of erythropoiesis: the mother's own red blood cell volume increases by 240–400 ml.
- Fetal iron uptake: the trace element is actively withdrawn from the maternal stores. The synthesis of just 1 gram of fetal hemoglobin requires 3.5 mg of maternal iron.
Factors contributing to iron store depletion:
- Inadequate dietary intake of the trace element or impaired gastrointestinal absorption.
- Bleeding due to obstetric pathology (threatened or inevitable miscarriage, partial placental abruption).
- Multiple pregnancy (demand for resources increases manifold).
- Early toxicosis (hyperemesis gravidarum).
- Short intergenerational interval (short gap between deliveries).
- Frequent deliveries accompanied by a prolonged lactation period.
Clinical presentation and diagnostics
The symptoms of IDA in pregnant women have no specific differences. Patients complain of generalized weakness, dizziness, dyspnea on exertion, and also note trophic disorders: hair loss and brittle nails. Laboratory screening plays a decisive role in making the diagnosis.
Diagnostic criteria for IDA:
- Hemoglobin (Hb): less than 110 g/L.
- Color index: less than 0.85.
- Serum iron: less than 12.5 µmol/L.
- Serum ferritin: less than 15 µg/L.
- TIBC (Total Iron-Binding Capacity of serum): elevated.
Erythrocyte indices are also evaluated: microcytosis (MCV < 80 fL), hypochromia (MCH < 30 pg), and anisocytosis (RDW > 14.5%) are detected.
Severity grades (by hemoglobin level):
- Mild: 90–110 g/L.
- Moderate: 70–89 g/L.
- Severe: less than 70 g/L.
Obstetric complications and fetal impact
The frequency and severity of complications directly depend on the degree and duration of the anemia. Mild anemia generally does not negatively affect the course of gestation, labor, or fetal condition.
Complications in severe IDA:
- For the mother: increased risk of spontaneous abortions, preterm labor, and uterine inertia. In the postpartum period, inflammatory complications and hypogalactia (insufficient breast milk production) are more common.
- For the fetus: chronic hypoxia and fetal growth restriction (FGR) develop.
- For the newborn: infants born to mothers with moderate and severe IDA initially have impaired iron metabolism parameters. This creates a high risk of developing anemia under 1 year of age.
Principles of treatment and prevention
The basis of conservative therapy is the prescription of oral iron supplements. The course of treatment must be prolonged and last at least 1–1.5 months.
Features of pharmacotherapy:
- Drugs of choice: preference is given to agents based on ferric (trivalent) iron, as they are significantly better tolerated by patients compared to ferrous (divalent) analogues.
- Absorption factors: treatment efficacy depends on the ionic formula of the metal and the presence of additional enhancer components in the preparation (ascorbic, citric, succinic acids, fructose) that improve absorption.
- Comprehensive approach: since anemia in pregnant women often has a mixed genesis, folic acid preparations must be included in the treatment regimen (or ready-made combination products used).
Prevention: According to WHO recommendations, prophylactic administration of iron supplements is advisable for all pregnant women. The optimal period is throughout the 2nd and 3rd trimesters (when active iron transfer to the fetus occurs), as well as during the first 6 months of lactation.
Briefly: answers to topical questions
What are the indications for parenteral (intravenous) administration of iron preparations during pregnancy?
Indications for parenteral administration of ferric iron preparations include severe anemia, ineffectiveness, or inability to use oral forms.
- Severe anemia — hemoglobin concentration drop below 70 g/L.
- Treatment failure — lack of response to oral iron supplements.
- Intolerance — poor tolerance of oral forms or presence of contraindications to oral administration.
- Ongoing blood loss — conditions requiring urgent replenishment of iron stores.
- Absorption disorders — malabsorption syndrome, inflammatory bowel disease, status post extensive bowel resection.
These indications are also relevant for postpartum women.
What pathologies require differential diagnosis for hypochromic microcytic anemia in pregnant women?
Differential diagnosis of hypochromic microcytic anemia is performed with conditions accompanied by disturbed iron metabolism or defective hemoglobin synthesis.
- Anemia of chronic disease — complicates the course of chronic inflammatory processes and malignancies.
- Thalassemias (alpha- and beta-thalassemias) — hereditary hemoglobinopathies with defective globin synthesis and iron overload.
- Sideroblastic anemias — conditions with impaired incorporation of iron into the heme structure despite its adequate quantity (pyridoxine-responsive anemia, porphyrin synthesis defect).
- Lead poisoning — accompanied by hypochromia and iron overload.
- Porphyrias — hypochromic anemias with iron overload.
- Other deficiency anemias presenting with a similar hematological picture.
To quickly memorize the laboratory markers of iron deficiency anemia (IDA), use the "Rule of Three Drops and One Rise": hemoglobin, ferritin, and serum iron drop, while total iron-binding capacity (TIBC) "rises" (increases).
Class and exam questions
Do we need to treat physiological anemia in pregnancy?
No, physiological hemodilution (a decrease in hematocrit due to a faster increase in plasma volume) is a variant of the norm and does not require specific drug therapy.
Why are iron supplements often prescribed along with folic acid?
In clinical practice, anemia in pregnancy often has a mixed genesis. Due to the high frequency of concomitant folate deficiency, combination therapy provides a more pronounced and lasting effect.
Does mild anemia affect fetal development?
As a rule, mild anemia (at a hemoglobin level of 90–110 g/L) has no negative impact on the course of pregnancy, labor, or the intrauterine condition of the fetus.
What else to study on this topic
- Transient gestational hyperthyroidism and Graves' disease
- Leukemia in pregnancy: risks and obstetric management
- Hodgkin's lymphoma (Hodgkin's disease) during gestation
- Idiopathic thrombocytopenic purpura (Werlhof's disease)
- Von Willebrand disease and risks of obstetric hemorrhage
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