A 3-day-old neonate born at 37 weeks presents with serum bilirubin of 18 mg/dL, predominantly indirect. The direct antiglobulin test (DAT/Coombs) is negative. The baby's blood group is A+ve and the mother's is O+ve. What is the MOST likely cause of jaundice?

• A ABO incompatibility ✓
• B Physiological jaundice
• C G6PD deficiency
• D Crigler-Najjar syndrome type I

Explanation

ABO incompatibility classically occurs with O-positive mother and A or B group neonate, and the DAT can be weakly positive or negative (unlike Rh disease where DAT is strongly positive). Bilirubin of 18 mg/dL at day 3 is pathological and exceeds typical physiological jaundice. G6PD deficiency is possible but requires a trigger exposure. Crigler-Najjar type I would present with extreme hyperbilirubinemia (>25 mg/dL) unresponsive to phenobarbitone and requires exchange transfusion repeatedly. The clinical scenario best fits ABO incompatibility.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.