A 3-day-old term neonate presents with jaundice. Total serum bilirubin is 22 mg/dL. Direct Coombs test is positive, and the mother is blood group O, Rh positive. The baby is blood group A, Rh positive. Which mechanism best explains this jaundice?
- A ABO incompatibility with anti-A IgG antibodies crossing the placenta ✓
- B Rh isoimmunization leading to extravascular hemolysis
- C G6PD deficiency triggered by hospital exposure
- D Physiological jaundice with delayed bilirubin conjugation
Correct answer: A. ABO incompatibility with anti-A IgG antibodies crossing the placenta
Explanation
ABO incompatibility is the most common cause of hemolytic disease of the newborn (HDN) in India. It occurs when the mother is group O and the baby is group A or B because O-group mothers naturally carry anti-A and anti-B antibodies, predominantly IgG, which cross the placenta. Unlike Rh disease, ABO HDN can occur in the first pregnancy and is usually milder. The positive direct Coombs test with O-group mother and A-group baby confirms this diagnosis.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.