Anaemia in Pregnancy

Anaemia in pregnancy is the single most common medical disorder complicating gestation in India, with a prevalence touching 50-60% of antenatal women. It is a favourite NEET PG topic because the haemoglobin cut-offs, WHO/ICMR grading, and the indications for parenteral iron are pure recall — easy marks if the exact numbers are memorised.

Definition & WHO Criteria

Anaemia is a reduction in the oxygen-carrying capacity of blood. In pregnancy the diagnosis is anchored to haemoglobin (Hb) concentration, because the haematocrit and RBC count are confounded by the physiological haemodilution of pregnancy.

High-yield: WHO defines anaemia in pregnancy as Hb < 11 g/dL (or haematocrit < 33%). This is the single most-asked cut-off. ICMR uses the same threshold.

There is a subtlety regarding the trimester. The CDC (and many newer guidelines) allow a slightly lower threshold in the second trimester because haemodilution peaks then:

Period	Anaemia if Hb below
1st trimester	11 g/dL
2nd trimester	10.5 g/dL (CDC)
3rd trimester	11 g/dL
Postpartum	10 g/dL

For NEET PG, when no trimester is specified, the answer is < 11 g/dL (WHO).

Grading of Severity (ICMR / WHO)

This table is directly examinable — learn it cold.

Grade	Haemoglobin (g/dL)
Mild	10.0 – 10.9
Moderate	7.0 – 9.9
Severe	4.0 – 6.9
Very severe / decompensated	< 4.0

High-yield: Hb < 7 g/dL = severe anaemia. Hb < 4 g/dL = very severe, an obstetric emergency carrying a high risk of cardiac failure, especially in labour and the immediate puerperium.

Mnemonic for the upper boundaries: "11 – 10 – 7 – 4" → normal floor, mild floor, moderate floor, severe floor.

Physiological (Dilutional) Anaemia of Pregnancy

This concept is a recurring distractor in MCQs. During pregnancy:

• Plasma volume increases by ~45-50% (≈ 1000-1250 mL).
• Red cell mass increases by only ~20-30% (≈ 250-450 mL).

Because plasma expansion outstrips RBC mass expansion, there is a dilutional fall in Hb and haematocrit that is maximal at 30-34 weeks (some texts say 32 weeks). This is physiological haemodilution, NOT true anaemia.

High-yield: Physiological anaemia of pregnancy is maximum at 30-34 weeks because plasma volume expansion peaks then; thereafter plasma volume plateaus while RBC mass keeps rising, so Hb rises slightly near term.

Distinguishing features of physiological vs pathological:

• Physiological: Hb usually ≥ 10 g/dL, normal red cell indices, normal peripheral smear.
• Pathological: Hb < 10 g/dL, or abnormal indices/smear → investigate.

Classification of Anaemia in Pregnancy

Flow of approach: Confirm low Hb → check MCV / peripheral smear → classify morphologically → confirm with specific tests → treat the cause.

1. Physiological (dilutional) — most common "apparent" cause.
2. Pathological / Deficiency anaemias:
   • Iron-deficiency anaemia (IDA) — the commonest true anaemia in pregnancy (~95% of cases in India).
   • Megaloblastic anaemia — folate >> vitamin B12 deficiency.
   • Dimorphic — combined iron + folate deficiency (very common in Indian women; smear shows microcytic + macrocytic populations).
3. Haemorrhagic — acute (APH/PPH) or chronic (hookworm, menorrhagia in earlier life, bleeding piles).
4. Anaemia of chronic disease — chronic infection, malaria, TB, chronic kidney disease.
5. Haemolytic — sickle cell disease, thalassaemia, malaria, autoimmune.
6. Aplastic / marrow failure — rare.

High-yield: Worldwide and in India, iron-deficiency anaemia is the most common cause of anaemia in pregnancy. The second commonest in India is folate-deficiency (megaloblastic) anaemia.

Etiology & Pathophysiology of Iron-Deficiency Anaemia

Pregnancy imposes a large iron demand. Total iron requirement of a pregnancy is about 1000 mg:

• ~300 mg actively transported to fetus and placenta.
• ~200 mg lost via gut, skin, urine (obligatory loss).
• ~500 mg for the expanded maternal red cell mass.

Against a daily absorption ceiling of ~2-4 mg, pre-existing depleted stores (common in Indian women due to repeated pregnancies, poor diet, hookworm, and menstrual losses) tip the balance into deficiency, especially in the second half of pregnancy.

Pathophysiology sequence: depleted stores → fall in serum ferritin → fall in serum iron, rise in TIBC → impaired haemoglobin synthesis → microcytic hypochromic red cells.

Clinical Features

• Easy fatigue, weakness, exertional dyspnoea, palpitations.
• Pallor (conjunctiva, nail beds, tongue, palms).
• Koilonychia (spoon-shaped nails), angular stomatitis, glossitis, brittle hair — features of long-standing IDA.
• Pica — craving for non-food items (ice = pagophagia, clay = geophagia).
• In severe anaemia: tachycardia, oedema, signs of high-output cardiac failure.

Diagnosis & Investigation of Choice

Stepwise: CBC + indices → peripheral smear → confirm aetiology with serum ferritin (iron status) → reticulocyte count → specific tests (B12/folate, Hb electrophoresis) as indicated.

Parameter	IDA	Megaloblastic
MCV	Low (< 80 fL) microcytic	High (> 100 fL) macrocytic
MCHC	Low (hypochromic)	Normal
Peripheral smear	Microcytic, hypochromic, anisopoikilocytosis, pencil cells, target cells	Macro-ovalocytes, hypersegmented neutrophils (≥ 5 lobes)
Serum ferritin	Low (< 12-15 ng/mL)	Normal/high
Serum iron	Low	Normal
TIBC	High	Normal/low
Transferrin saturation	Low (< 16%)	Normal
Reticulocyte count	Low	Low
Bone marrow	Micronormoblastic, absent stainable iron	Megaloblastic erythropoiesis

High-yield: Serum ferritin is the single most sensitive and earliest indicator of iron-deficiency anaemia (reflects body iron stores) — ferritin < 12-15 ng/mL is diagnostic of depleted stores. Caveat: ferritin is an acute-phase reactant and may be falsely normal/raised in infection or inflammation.

High-yield: The earliest, most specific peripheral-smear finding in megaloblastic anaemia is the hypersegmented neutrophil (≥ 5 lobes), which appears before macrocytosis.

For megaloblastic anaemia, distinguish folate vs B12: folate deficiency is far commoner in pregnancy (increased demand for rapid cell division). B12 deficiency is rare in pregnancy and, if present, does NOT cause neurological signs from folate therapy unless masked — but never give folate alone if B12 deficiency is suspected, to avoid subacute combined degeneration.

Management & Drug of Choice

Prophylaxis (Government of India / WHO)

High-yield: Routine antenatal prophylaxis under the Anaemia Mukt Bharat / National programme = 60 mg elemental iron + 500 µg (0.5 mg) folic acid daily for at least 100 days, started after the first trimester (after 14-16 weeks) and continued for 100 days postpartum. WHO recommends 30-60 mg elemental iron daily.

Folic acid for neural tube defect prevention: 400 µg/day periconceptionally and through the first trimester; 4-5 mg/day for high-risk women (previous NTD-affected baby, on antiepileptics, diabetes).

Treatment of Established Iron-Deficiency Anaemia

Oral iron is the drug of first choice when the anaemia is mild-to-moderate, gestation allows time to respond, and the patient tolerates it.

• Therapeutic dose: ~100-200 mg elemental iron/day in divided doses.
• Ferrous sulphate 325 mg contains ~65 mg elemental iron; ferrous fumarate ~33%, ferrous gluconate ~12% elemental iron.
• Best absorbed on an empty stomach with vitamin C; avoid with tea, calcium, antacids.
• Response marker: reticulocytosis peaks at 5-10 days; Hb rises by ~0.8-1 g/dL per week (~2 g/dL over 3 weeks). Continue iron for 3 months after Hb normalises to replenish stores.

Parenteral (Intravenous) Iron — Indications

High-yield: Indications for parenteral/IV iron in pregnancy: (1) intolerance/non-compliance with oral iron, (2) malabsorption, (3) need for rapid replenishment — moderate-to-severe anaemia diagnosed after 30 weeks with insufficient time before delivery, (4) severe anaemia where transfusion is to be avoided.

• Preferred agents: iron sucrose and ferric carboxymaltose (FCM). FCM allows large single doses (up to 1000-1500 mg) and is increasingly first-line.
• Iron dextran is largely abandoned in pregnancy due to anaphylaxis risk.
• IM iron (iron sorbitol) is painful, causes skin staining, and is rarely used now.
• Total dose to replace = deficit + stores; a working formula: Iron deficit (mg) = 2.4 × weight (kg) × (target Hb − actual Hb) + 500 mg (stores).

Blood Transfusion

High-yield: Indications for transfusion: severe anaemia (Hb < 7 g/dL) near term (after ~36 weeks) with no time for iron to act, decompensated anaemia/cardiac failure, anaemia with ongoing/anticipated haemorrhage, or refractory anaemia. Packed red cells are preferred; in cardiac failure give slowly with diuretic cover (or exchange transfusion in very severe anaemia near labour).

Megaloblastic Anaemia Treatment

• Folic acid 5 mg/day orally is the drug of choice; add iron (deficiency is usually combined).
• If B12 deficiency confirmed: parenteral hydroxocobalamin/cyanocobalamin.
• Haematological response: reticulocytosis in 3-5 days, falling MCV.

Effects & Complications

Maternal: preterm labour, pre-eclampsia, intercurrent infection, poor wound healing, postpartum haemorrhage tolerance is poor (even modest blood loss is dangerous), puerperal sepsis, failure of lactation, and in severe cases high-output cardiac failure — the danger periods are during labour, immediately after delivery (sudden venous return), and early puerperium.

Fetal/neonatal: intrauterine growth restriction (IUGR), low birth weight, prematurity, increased perinatal mortality, and reduced fetal iron stores predisposing to infantile anaemia.

High-yield: Anaemia is an important indirect cause of maternal mortality in India and contributes to a large share of maternal deaths, mostly by worsening the outcome of haemorrhage and infection.

Key Differentials

• Physiological haemodilution — Hb ≥ 10, normal indices/smear; no treatment beyond routine prophylaxis.
• Thalassaemia trait — microcytosis out of proportion to anaemia, normal/raised RBC count, normal-to-high ferritin, raised HbA2 (β-thal) on electrophoresis. Mentzer index (MCV/RBC count) < 13 suggests thalassaemia, > 13 suggests IDA.
• Anaemia of chronic disease — low serum iron AND low TIBC, ferritin normal/high.
• Sickle cell disease — sickling test/electrophoresis; sickle crises in pregnancy.

Feature	IDA	Thalassaemia trait	Anaemia of chronic disease
Serum iron	↓	Normal	↓
TIBC	↑	Normal	↓
Ferritin	↓	Normal/↑	Normal/↑
RBC count	↓	Normal/↑	↓
Mentzer index	> 13	< 13	variable

Recently asked / exam angle

• WHO cut-off for anaemia in pregnancy = Hb < 11 g/dL — repeated almost every cycle.
• Severe anaemia = Hb < 7 g/dL, very severe < 4 g/dL — grading-based single-best-answer questions.
• Maximum physiological anaemia at 30-34 weeks due to peak plasma volume expansion.
• Commonest anaemia = iron-deficiency; commonest cause overall; second commonest in India = folate-deficiency megaloblastic.
• Serum ferritin = best/earliest indicator of iron stores; falsely raised in inflammation.
• Anaemia Mukt Bharat: 60 mg elemental iron + 500 µg folic acid in pregnancy.
• Indications for IV iron and transfusion thresholds are classic "single best response" stems.
• Hypersegmented neutrophil as the earliest smear sign of megaloblastic anaemia.
• Image-based: pencil cells / koilonychia for IDA; macro-ovalocytes for megaloblastic.
• Mentzer index to separate IDA from thalassaemia trait.

Rapid revision

1. WHO anaemia in pregnancy = Hb < 11 g/dL (Hct < 33%).
2. Grading: mild 10-10.9, moderate 7-9.9, severe < 7, very severe < 4 g/dL.
3. Plasma volume rises ~50%, RBC mass ~25% → dilutional anaemia maximal at 30-34 weeks.
4. Total pregnancy iron requirement ≈ 1000 mg; ~300 mg to fetus.
5. Commonest true anaemia = iron deficiency (microcytic hypochromic, pencil cells).
6. Serum ferritin < 12-15 ng/mL = best early marker of iron deficiency.
7. Megaloblastic anaemia in pregnancy = mostly folate deficiency; hallmark = hypersegmented neutrophils, treat with folic acid 5 mg/day.
8. Prophylaxis (Anaemia Mukt Bharat) = 60 mg elemental iron + 500 µg folate/day.
9. Oral iron therapeutic dose ~100-200 mg elemental iron/day; ferrous sulphate 325 mg = 65 mg elemental.
10. Response: reticulocytosis at ~5-10 days, Hb ↑ ~1 g/dL/week; continue iron 3 months after Hb normalises.
11. IV iron (iron sucrose/FCM) if oral intolerance, malabsorption, or diagnosis after 30 weeks needing rapid correction.
12. Transfuse if Hb < 7 g/dL near term, cardiac failure, or ongoing haemorrhage — packed cells, slowly, with diuretic cover.