Anaemia in Pregnancy

Plasma volume expands by roughly 40 to 50% in pregnancy while red cell mass rises by only about 20 to 30%, producing a physiological, dilutional fall in hemoglobin even without true iron deficiency.

True anemia, however, is common and predominantly iron deficiency related, driven by increased fetal, placental, and maternal red cell iron demand, frequently compounded by suboptimal dietary intake or absorption.

Fatigue, pallor, dyspnea, and palpitations, though many cases are asymptomatic and identified on routine screening.

Severe anemia increases the risk of preterm birth and low birth weight, and reduces tolerance of postpartum hemorrhage.

• WHO thresholds for anemia in pregnancy: hemoglobin under 110 g/L in the first and third trimester, under 105 g/L in the second trimester (reflecting the physiological dilutional nadir), and under 100 g/L postpartum
• FBC and ferritin (an acute phase reactant, interpret cautiously in the presence of infection or inflammation); hemoglobinopathy screening per population risk; B12 and folate assessment if macrocytic

• Routine supplementation: WHO recommends 30 to 60 mg elemental iron plus 400 mcg folic acid daily throughout pregnancy in populations with high anemia prevalence; in lower prevalence settings, a screen-and-treat approach is used instead in many guidelines
• Confirmed iron deficiency anemia: ferrous sulfate 200 mg PO od-bd (providing roughly 65 mg elemental iron per tablet), with alternate-day dosing increasingly preferred given improved absorption and reduced GI side effects; recheck hemoglobin after 2 to 4 weeks, expecting a rise of roughly 10 to 20 g/L over 3 to 4 weeks
• IV iron (ferric carboxymaltose or iron sucrose, dosed by weight and calculated hemoglobin deficit) for oral intolerance, malabsorption, or where rapid correction is needed, such as significant anemia approaching term, or hemoglobin under 90 to 100 g/L later in pregnancy
• Blood transfusion reserved for severe, symptomatic anemia or significant acute blood loss, not for correction of chronic, stable iron deficiency alone
• Folate 400 mcg to 5 mg PO od per risk category as detailed in the Normal Pregnancy entry; B12 replacement (IM hydroxocobalamin per standard protocol, see Vitamin B12 Deficiency Anaemia entry) if deficient
• Screen for and treat any underlying contributing cause beyond simple dietary deficiency, notably malaria in endemic settings (a major global contributor to pregnancy anemia), hookworm, or an underlying hemoglobinopathy

Referral: hematology for suspected hemoglobinopathy, anemia not responding to oral iron, or where complex IV iron or transfusion decisions are needed.