Rh Disease

September 26, 2011

Rh disease is known as hemolytic (having to do with the blood) disease of the newborn (erythroblastosis fetalis). Rh refers to the Rh system (antigen groups include C, D, E) on blood cells and specifically the D-antigen. Rh disease develops when antibodies form in an individual with Rh-negative (lack of D-antigen) blood after exposure to red blood cells that have a D-antigen (Rh-positive) within the blood. Antibodies are cells of the immune system that identify other cells or compounds in the body or blood that the immune system perceives as dangerous. Among racial groups, the Rh-negative blood group is more common among whites (15%) than African Americans (5-8%) or Asians/Native Americans (1-2%).
Rh disease has a wide variety of presentations from mild hemolysis (anemia caused by the breakdown of red blood cells) to hydrops fetalis (a severe, life-threatening problem of severe edema [swelling] in the fetus and newborn). An Rh-negative woman during her first pregnancy will probably have some exposure to fetal blood; if the fetus is Rh-positive, the woman may develop antibodies (IgG) to the D-antigen on the fetal red blood cells. The infant from the first pregnancy may exhibit few or no signs of hemolysis (red blood cell breakdown) and only have mild signs of jaundice after birth. During subsequent pregnancies, a fetus, if Rh-positive, may be at increased risk for complications due to mother’s Rh-negative blood group.

LABORATORY EVALUATION

In the case of suspected Rh incompatibility (the mother being Rh-positive and the fetus Rh-negative), laboratory data of infant and maternal blood groups should be identified. The infant will need a variety of specialized blood tests (a Coomb’s test, hemoglobin, reticu-locyte count, total and direct bilirubin level, and a blood smear). In the presence of hemolytic disease, some of these blood tests will be abnormal (the Coomb’s test will be positive, there will be evidence of anemia on the hemoglobin, the reticulocyte count will be increased, there will be abnormal cells on the blood smear, and the total [unconjugated] bilirubin will be elevated).

INFANT PRESENTATION OF Rh DISEASE

The characteristic presentation of an infant (Rh-positive) born to a mother (Rh-negative) will be yellowing of skin and whites of the eyes (jaundice) within the first day of life. While the infant was in utero, the bilirubin was cleared by the placenta. The infant will not be able to handle the red cell waste products (bilirubin by-products) being produced by the breakdown (hemolysis) of red blood cells occurring due to the maternal antibodies that have crossed into the infant’s blood prior to delivery via the placenta. Jaundice due to hemolysis of red blood cells puts infants at greater risk for kernicterus (a buildup of bilirubin in the brain), which may include symptoms of flaccidity (weakness), opisthotonus (a spasm of the spine and extremities), seizures, apnea, and even death. Treatment of Rh disease includes a specialized form of light exposure therapy (phototherapy) and possibly blood exchange transfusion (remove damaged blood and replace with healthy blood).

Infants with a more severe presentation of Rh disease, hydrops fetalis, require immediate diagnosis and supportive therapy. Signs of more severe disease include pallor (anemia), edema (hypoalbuminemia), pleural and cardiac effusions (fluid around the lungs and heart), hepatosplenomegaly (enlarged liver and spleen), petechiae (a rash of tiny red bumps from a low platelet count that does not blanch when pressed on), or ascites (fluid in the abdomen). These infants will often need the care of a neonatal intensive care unit for monitoring, temperature stabilization, respiratory support, correction of abnormal blood acid balance (metabolic acidosis), and exchange transfusion. An exchange transfusion involves exchanging two blood volumes of the infant’s blood with the donor’s blood. The exchange transfusion should help to remove bilirubin and hemolyzing red blood cells (about 85%).

PREVENTION OF Rh DISEASE

Prevention of Rh disease is done by screening maternal blood type. If the woman is Rh-negative, she should have a specific blood product, anti-D gamma globulin or RhoGAM, given between 20 and 28 weeks gestation, at the end of pregnancy (delivery, miscarriage, or abortion) or in the case of blood transfusion, amniocentesis or vaginal bleeding during the pregnancy. An Rh-negative woman should be monitored during pregnancies for increasing levels of antibody. If the Rh-antibody levels are increasing or there is previous history of an infant with Rh disease, then close fetal monitoring is required with ultrasound and specific procedures that sample small pieces of the placenta, or tissues and fluids that surround the fetus (chorionic vil-lus sampling, amniocentesis, or percutaneous umbilical blood sampling). The overall incidence of Rh-negative mothers with multiple pregnancies having an infant with hemolytic disease is around 5%.

RhoGAM has revolutionized Rh disease for most mothers and babies. What was once a commonly devastating and deadly disease is now one seen much more rarely and less severely.

See Also: Labor and delivery, Neonatal care ethics, Pregnancy, Prenatal care, Reproductive technologies

Suggested Reading

  • Behrman, R. E., Kliegman, R. M., & Jenson, H. B. (Eds.). (2000). Hemolytic disease of the newborn. Nelson’s textbook of pediatrics (pp. 521-525). Philadelphia: W.B. Saunders.
  • Gabbe, S. G., Niebyl, J. R., & Simpson, J. L. (Eds.). (2002). Rh disease. Obstetrics, normal and problem pregnancies (pp. 893-915). New York: Churchill Livingstone.
  • Stockman, J. A. (2001). Overview of the state of the art in Rh disease: History, current clinical management, and recent progress. Journal of Pediatric Hematology/Oncology, 23(8), 554-562.

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