A term neonate develops jaundice on day 1 of life. Total bilirubin is 14 mg/dL at 18 hours of age. Blood group: mother O negative, baby A positive. DCT (direct Coombs test) is positive. What is the most likely cause?
- A Physiological jaundice
- B Rh (D) isoimmunisation
- C G6PD deficiency
- D ABO incompatibility with haemolytic disease of the newborn ✓
Explanation
Jaundice appearing within the first 24 hours of life is always pathological and most commonly due to haemolytic disease. A positive DCT (direct Coombs test) indicates antibody-coated red cells, confirming immune haemolysis. Given an O-negative mother and A-positive baby, the scenario fits ABO incompatibility — anti-A IgG antibodies from a group O mother cross the placenta and haemolyse fetal A antigens. Rh isoimmunisation is less likely in a first pregnancy without prior sensitisation (though the mother is Rh-negative, no prior Rh-sensitisation history is given and clinical features fit ABO better here). Physiological jaundice never appears in the first 24 hours. G6PD deficiency produces DCT-negative haemolysis.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.