Rh disease

Rh disease

Blood Type Compatability

Rh disease, also known as rhesus isoimmunisation, Rh (D) disease, rhesus incompatibility, and several other names, is a form of hemolytic disease of the newborn (HDN). This condition can manifest in varying degrees of severity and is particularly evident in certain subsequent pregnancies when an Rh-negative mother carries an Rh-positive fetus, a result of an Rh-positive father.

Newborn infant with severe Rhesus disease, suffering from hydrops fetalis

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Etiology

The disease arises primarily during the birth process, when the mother may come into contact with the infant's blood. Subsequent exposure can lead to the mother's immune system developing antibodies against the Rh factor in the fetus's blood. This immunological response can affect the health of subsequent Rh+ pregnancies.

Symptoms and Progression

In its milder forms, the fetus may experience only slight anemia accompanied by reticulocytosis. More pronounced cases can result in notable fetal anemia and erythroblastosis fetalis, another manifestation of HDN. In its most severe instances, Rh disease can precipitate hydrops fetalis or even stillbirth.

Serology

A small volume of fetal blood can enter the maternal circulation during pregnancy. If the mother's blood is Rh-negative and the baby's Rh-positive, the mother may produce antibodies against the rhesus D antigen on the baby's red blood cells. These antibodies, particularly IgG, can cross the placenta in this and subsequent pregnancies, and if present in sufficient quantities, can lead to the onset of Rh disease. This process can be seen as a form of diminished immune tolerance during pregnancy. Notably, the probability of Rh disease sensitization increases when the fetus and mother have compatible ABO blood types.

Diagnosis

• Maternal Blood
  • Kleihauer–Betke test and flow cytometry can confirm fetal blood entry into maternal circulation and estimate its volume.
  • The indirect Coombs test identifies IgG antibodies potentially harmful to the fetus.
  • Cell-free DNA testing can detect specific fetal DNA antigens non-invasively.
  • Blood tests can determine the probability of the fetus inheriting particular antigens and the resultant risk of HDN.
• Fetal Blood (or Umbilical Cord Blood)
  • Direct Coombs test checks for immune-mediated fetal anemia.
  • A complete blood count provides important values such as hemoglobin and platelet count.
  • Bilirubin, reticulocyte count, neutrophil count, thrombocyte count, ferritin, and others are assessed for a comprehensive diagnosis.

Prevention

The majority of Rh disease instances can be preempted by treating the mother either during pregnancy or shortly after childbirth. Typically, an intramuscular injection of anti-RhD immunoglobulin (Rho(D) immune globulin) is administered to degrade any fetal rhesus D positive erythrocytes before the mother's immune system can identify and respond to them.

Modern Antenatal Care

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Current antenatal protocols dictate that all Rh-negative pregnant women receive an anti-RhD IgG immunoglobulin injection around 28 weeks of gestation. This practice addresses the majority of sensitizing events which predominantly occur post the 28-week mark.

Management

• Antenatal
  • Ultrasound and Doppler examinations for early detection.
  • Intrauterine and intravascular blood transfusion methods.
• Early delivery considerations.
• Postnatal
  • Phototherapy and exchange transfusion based on disease severity.
  • Use of IVIG for effective treatment and reduction in the need for other interventions.

See Also

• Hemolytic disease of the newborn
• Rhesus factor
• Antenatal care
• Coombs test
• Hemolytic disease of the newborn
• Hemolytic anemia
• Hematology
• James Harrison: Australia's "Man With The Golden Arm"

External links

Classification	ICD-10: P55.0 ICD-9-CM: 773.0
External resources	MedlinePlus: 001600

• National institute of Clinical Excellence (NICE) Guidelines for anti-D prophylaxis
• Summary of transfusion reactions in the US

Rh disease Resources
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