Haemolytic disease of the newborn

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💉 Administering Anti-D immunoglobulin prevents the maternal immune system from forming antibodies against Rh antigen, protecting future Rh-positive pregnancies from haemolytic disease.

👶 About Haemolytic Disease of the Newborn (HDN)

• 🔴 Caused by haemolysis within the fetus due to maternal antibodies against the Rhesus (Rh) antigen.
• 🧬 Most common cause = Rh incompatibility, though other blood group incompatibilities (e.g., Kell, Duffy) may rarely be responsible.

⚙️ Aetiology

• Occurs in Rh-negative mothers previously exposed to Rh-positive blood (via prior pregnancy or transfusion).
• On re-exposure, maternal IgG antibodies cross the placenta 🪙 → destroy fetal RBCs → anaemia + jaundice.

🩺 Clinical Features

• 💛 Jaundice: Appears soon after birth due to bilirubin rise.
• 📈 Severe Hyperbilirubinaemia: Risk of neurological injury.
• ❤️ Anaemia: Due to ongoing haemolysis.
• 🧠 Kernicterus: Bilirubin deposition in brain → seizures, long-term damage.
• 💧 Hydrops Fetalis: Severe generalised oedema + high-output cardiac failure → often fatal.

🔍 Investigations

• 🩸 Blood typing: Fetal Rh status.
• 🧪 Direct Coombs (DAT): Detects antibody-coated fetal RBCs.
• 📉 RBC count: Reduced.
• 🧬 Reticulocytosis + Macrocytosis: Immature, large RBCs due to marrow response.
• 🎨 Polychromasia: Mixed-colour RBCs (active haemolysis).
• 🔴 Microspherocytes: Small spherical RBCs on blood film.

💊 Management

• 💉 Transfusion: Correct severe anaemia.
• 💧 Hydration: Maintain circulation + bilirubin clearance.
• ☀️ Phototherapy: Converts bilirubin to excretable form.
• 🔄 Exchange transfusion: Removes bilirubin + antibody-coated RBCs in severe cases.

🛡️ Prevention

• 👩‍🍼 All Rh-negative mothers at risk should receive Anti-D immunoglobulin (e.g., after delivery, miscarriage, amniocentesis, trauma).
• ✅ Administer Anti-D post-delivery if the infant is Rh-positive to prevent maternal sensitisation.

Cases - Haemolytic Disease of the Newborn (HDN)

• Case 1 - Rhesus incompatibility 🩸: A 28-year-old Rh-negative mother gives birth to a term infant who is jaundiced within 6 hours of birth. The baby is anaemic, with hepatosplenomegaly. Coombs (DAT) positive, bilirubin rapidly rising. Diagnosis: HDN due to Rh(D) incompatibility. Managed with intensive phototherapy and exchange transfusion if bilirubin continues to rise. Mother will require anti-D prophylaxis in future pregnancies.
• Case 2 - ABO incompatibility 🧬: A 32-year-old group O mother delivers a baby with blood group A. The neonate develops mild jaundice at 12 hours, but bilirubin rises slowly, anaemia is mild. Coombs positive. Diagnosis: ABO incompatibility causing HDN. Managed conservatively with phototherapy; condition usually less severe than Rh disease.
• Case 3 - Severe hydrops fetalis 🌊: A 25-year-old multiparous Rh-negative woman presents at 34 weeks with reduced fetal movements. Ultrasound: gross fetal oedema, ascites, cardiomegaly, and polyhydramnios. Intrauterine transfusion attempted but baby is delivered stillborn. Diagnosis: severe HDN with hydrops fetalis. Prevention: routine anti-D prophylaxis in Rh-negative mothers and monitoring with middle cerebral artery Doppler in sensitised pregnancies.

Teaching Point 🩺: HDN occurs when maternal IgG antibodies cross the placenta and destroy fetal RBCs. Causes include Rh(D) incompatibility (most severe), ABO incompatibility, and rare other blood group antigens. Complications: jaundice, anaemia, kernicterus, hydrops fetalis. Management = phototherapy, exchange transfusion, and prevention with maternal anti-D prophylaxis.