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ABO incompatibiity


ABO incompatibility (isoimmunisation) usually occurs when the mother is blood group O and the baby is group A, or less often, group B. Individuals with type O blood develop antibodies throughout life from exposure to antigens in food, Gram-negative bacteria or blood transfusion, and by the time of the first pregnancy, may already have high levels of serum anti-A and anti-B antibodies, which can attack the red blood cells in the fetus resulting in haemolysis (Haemolytic disease of the newborn). Severe haemolysis is less common with ABO incompatibility than with rhesus D incompatibility, but the midwife should be alert to the possibility in women with group O blood.

ABO incompatibility usually manifests at less than 36 hours of age, although it may not become obvious until after 48 hours. Diagnostic findings include jaundice, pallor and enlarged liver and spleen (hepatosplenomegaly).

Babies diagnosed and treated for ABO incompatibility need to be closely observed for signs of late anaemia which may occur due to ongoing haemolysis by antibodies that may persist in the baby's circulation for several weeks. Symptoms include lethargy, pallor and poor feeding history. Folate and iron may be prescribed to encourage red blood cell production but it is not unusual for a baby to develop a severe anaemia requiring transfusion. Continuity of care by the midwife providing care up to 28 days can be helpful.

The Practising Midwife featured article

Phototherapy TPM 2012, 4: 36-39 Author: Baston, Helen 



Willacy H. (2012) Haemolytic Disease of the Newborn (Professional reference).

Canadian Paediatric Society (2007, reaffirmed 2016) Guidelines for detection, management and prevention of hyperbilirubinemia in term and late preterm newborn infants.

National Institute for Health and Care Excellence. (2010) Jaundice in newborn babies under 28 days. Clinical guideline 98.

National Blood and Transplant Service. Blood Groups

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