Rh incompatibility

Causes and Risks:

During pregnancy , red blood cells from the fetal circulation leak into the maternal circulation. If the mother is Rh negative, her system will not tolerate the presence of Rh positive cells. Her immune system treats the Rh positive fetal cells as if they were a foreign protein or substance and makes antibodies against the fetal blood cells. These anti-Rh positive antibodies move through the placenta into the fetus where they destroy the fetus' circulating red blood cells. First-born infants are often not affected (unless the mother has had previous interrupted pregnancies, which could have sensitized her system) as it takes time for the mother to develop antibodies against the fetal blood.

Rh incompatibility may cause symptoms ranging from very mild to death of the newborn. In its mildest form, Rh incompatibility causes hemolysis (destruction of the red blood cells) with the release of free hemoglobin into the infant's circulation. Hemoglobin is converted into bilirubin , which causes an infant to become yellow (jaundiced). The jaundice of Rh incompatibility, measured by the level of bilirubin in the infant's bloodstream, may range from mild to dangerously high levels.

Hydrops fetalis is a complication or severe form of Rh incompatibility where massive fetal red blood cell destruction (a result of the Rh incompatibility) causes a severe anemia resulting in fetal heart failure , total body swelling , respiratory distress (if the infant has been delivered), and circulatory collapse. Hydrops fetalis often results in death of the infant shortly before or after delivery.

Kernicterus is a neurological syndrome caused by deposition of bilirubin into the brain (CNS) tissues. Kernicterus develops in extremely jaundiced infants, especially those with severe Rh incompatibility. It occurs several days after delivery and is characterized initially by loss of the Moro (startle) reflex, poor feeding , and decreased activity. Later a high-pitched shrill cry may develop along with unusual posturing, a bulging fontanel, and seizures . Infants may die suddenly of kernicterus. If they survive they later develop decreased muscle tone , movement disorders, high-pitched hearing loss , seizures, and decreased mental ability.

Rh incompatibility develops only when the mother is Rh negative and the infant is Rh positive. Special immune globulins, called RhoGAM, are now used to prevent this sensitization. Hydrops fetalis and kernicterus have almost disappeared as the result of preventive measures.

Prevention:
Rh incompatibility is almost completely preventable. Rh negative mothers should be followed closely by their obstetricians during pregnancy . If the father of the infant is Rh positive, the mother is given a mid-term injection of RhoGAM and a second injection within a few days of delivery. These injections prevent the development of antibodies against Rh positive blood. This effectively prevents the condition.

Symptoms:



Signs and Tests:


Mild Rh incompatibility:

Hydrops fetalis:

Early:

  • high bilirubin level (greater than 18 mg/cc)
  • extreme jaundice
  • absent Moro (startle) reflex
  • poor suck
  • lethargy

Mid:

Late--full neurological syndrome:



Treatment:
Since Rh incompatibility is almost completely preventable with the use of RhoGAM, prevention remains the best treatment. Treatment of the already affected infant depends on the severity of the condition.

Mild:

Hydrops fetalis:

  • amniocentesis to determine severity
  • intrauterine fetal transfusion
  • early induction of labor
  • a direct transfusion of packed red blood cells (compatible with the infant's blood) and also exchange transfusion of the newborn to rid the blood of the maternal antibodies that are destroying the red blood cells.
  • control of congestive failure and fluid retention

Kernicterus:

  • exchange transfusion (may require multiple exchanges)
  • phototherapy



Prognosis:
Full recovery is expected for mild Rh incompatibility. Both hydrops fetalis and kernicterus represent extreme conditions caused by hemolysis . Both have guarded outcomes. Hydrops fetalis has a high mortality rate.

Complications:



Call Your Healthcare Provider:

Call your health care provider if you think or know you are pregnant and have not yet seen a doctor.


Antibodies from an Rh negative mother may enter the blood stream of her unborn Rh positive infant, damaging the red blood cells (RBCs). The infant responds by increasing RBC production and sending out immature RBCs that still have nuclei. This photograph shows normal RBCs, damaged RBCs, and immature RBCs that still contain nuclei.



Newborn jaundice (producing yellow skin) can have many causes, but the majority of these infants have a condition called physiological jaundice, a natural occurrence in the newborn due to the immature liver. This type of jaundice is short term, generally lasting only a few days. Jaundice persisting longer than 3 to 4 days, or worsening rapidly, should be evaluated by a physician until decreasing or normal levels of bilirubin are measured in the blood.