What are the implications of ABO (Blood Group) incompatibility on pregnancy and the fetus?

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DS

Dainyal Siddiqui, MD

Internal Medicine

MJ

Manuel Jimenez, MD

Cardiology

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Franz Pierre-Louis, MD

Infectious Disease

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Last updated: March 17, 2025 • View editorial policy

From the Guidelines

ABO incompatibility in pregnancy rarely causes severe hemolytic disease of the newborn and typically presents as mild neonatal jaundice after birth, requiring no prenatal treatment or monitoring, but rather postnatal management with phototherapy or exchange transfusion in rare cases. The implications of ABO incompatibility on pregnancy and the fetus are generally mild, with the primary concern being neonatal jaundice within the first 24 hours of life 1. Unlike Rh incompatibility, ABO incompatibility is less severe due to the nature of the maternal anti-A and anti-B antibodies, which are primarily IgM and do not cross the placenta efficiently.

Key Considerations

  • ABO incompatibility occurs when a mother and her fetus have different ABO blood types, most commonly when a mother with type O blood carries a fetus with type A, B, or AB.
  • The condition is self-limiting as fetal cells gradually disappear from neonatal circulation, and long-term complications are rare with appropriate monitoring and treatment.
  • Blood typing of both mother and baby is recommended, and healthcare providers should be vigilant for jaundice in newborns with potential incompatibility.
  • Management focuses on monitoring and treating jaundice if it develops, usually with phototherapy, and in rare severe cases, exchange transfusion may be necessary.

Evidence-Based Recommendations

  • All pregnant women should be tested for ABO and Rh (D) blood types and have a serum screen for unusual isoimmune antibodies, as recommended by the Pediatrics journal in 2004 1.
  • The Society for Maternal-Fetal Medicine (SMFM) clinical guideline #8 provides an algorithm for the diagnosis of fetal anemia in the pregnancy complicated by red cell alloimmunization, but this is more relevant to Rh incompatibility and other causes of fetal anemia 2, 3.

Clinical Implications

  • No prenatal treatment or monitoring is typically required for ABO incompatibility during pregnancy, but rather postnatal management and monitoring for jaundice.
  • Healthcare providers should be aware of the potential for ABO incompatibility and its implications on the fetus and newborn, and take appropriate steps to monitor and manage the condition.

From the FDA Drug Label

INDICATIONS AND USAGE Pregnancy and Other Obstetric Conditions HyperRHO S/D Full Dose is recommended for the prevention of Rh hemolytic disease of the newborn by its administration to the Rho(D) negative mother within 72 hours after birth of an Rho(D) positive infant, If HyperRHO S/D Full Dose is administered antepartum, it is essential that the mother receive another dose of HyperRHO S/D Full Dose after delivery of an Rho(D) positive infant.

The implications of ABO (Blood Group) incompatibility on pregnancy and the fetus are not directly addressed in the provided drug label. The label discusses Rh incompatibility, not ABO incompatibility. Key points to consider:

  • The label only discusses the prevention of Rh hemolytic disease of the newborn.
  • There is no information on ABO blood group incompatibility. 4

From the Research

Implications of ABO Incompatibility on Pregnancy and the Fetus

  • ABO incompatibility between mother and child can reduce the risk of D immunization and subsequent hemolytic disease of the fetus and newborn (HDFN) 5.
  • However, ABO incompatibility does not protect against anti-human platelet antigen-1a immunization by pregnancy 6.
  • In some cases, ABO incompatibility can lead to severe fetal anemia, particularly when the mother has elevated titers of IgG anti-B antibodies 7.
  • Maternal ABO-mismatched blood can be used for intrauterine transfusion in cases of severe hemolytic disease of the newborn due to anti-Rh17, when antigen-negative blood is difficult to obtain 8.
  • The use of Rh-immunoglobulin (Rh-Ig) has reduced the incidence of hemolytic disease of the newborn (HDNB) due to Rho (D) incompatibility, but has no effect on ABO or non-ABO, non-D incompatibilities 9.

Effects on Fetal and Neonatal Health

  • ABO incompatibility can lead to hemolysis and anemia in the fetus and newborn, particularly in cases where the mother has high titers of anti-B antibodies 7.
  • Intrauterine transfusion with maternal ABO-mismatched blood can help alleviate severe anemia and hemolytic disease of the newborn 8.
  • The expression of blood group A antigens on platelets in newborns is similar to that in adults, but at a lower level, which may affect the severity of fetal and neonatal alloimmune thrombocytopenia 6.

Management and Prevention

  • Rh-immunoglobulin (Rh-Ig) can prevent sensitization to Rho (D) in 85-90% of cases, but has no effect on ABO or non-ABO, non-D incompatibilities 9.
  • Intrauterine transfusion with maternal ABO-mismatched blood can be used in cases where antigen-negative blood is difficult to obtain 8.
  • Monitoring of fetal and neonatal health is crucial in cases of ABO incompatibility, particularly when the mother has high titers of anti-B antibodies 7.

References

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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