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Rh Incompatibility

Rh Incompatibility

Alternate Names

  • erythroblastosis fetalis
  • kernicterus
  • hydrops fetalis
  • Rh isoimmunization

Definition

Rh incompatibility is a condition that occurs when a woman has Rh-negative blood type and her unborn child or newborn has Rh-positive blood. This incompatible blood reaction may cause problems in a newborn as well as life-threatening problems for future pregnancies.

What is going on in the body?

The Rh factor, or Rhesus factor, is a marker that may or may not be present on the surface of a person's red blood cells.
When a woman has the Rh component in her blood, she is considered Rh positive. When she does not have the Rh factor, she is considered Rh negative.
When a person who has Rh-negative blood is exposed to Rh-positive blood, that person's body does not recognize the Rh factor and considers it something foreign. The body builds antibodies against it as it would for any foreign substance that is introduced into the blood.
If the person who is Rh negative is ever exposed in the future to Rh-positive blood, his or her body is armed to attack the red blood cells that have the Rh factor.
Therefore, problems may arise if a woman with Rh-negative blood conceives a baby who has Rh-positive blood. (This may occur if the father of the baby has Rh-positive blood.)
The pregnant woman's body can become sensitive to the Rh factor and build up "antibodies" to attack the Rh factor. The build up of antibodies does not usually occur until after delivery of the newborn. However, not all women develop antibodies to the Rh factor after having one baby with Rh-positive blood.
Generally, there is no effect on the first-born child. If problems occur, they generally happen in second and later pregnancies.
For example, say a woman who is Rh negative becomes pregnant again and her unborn baby has Rh-positive blood. The Rh antibodies that the woman may have developed during or after her first pregnancy can pass through the blood to her second baby and attack the baby's red blood cells.
This attack can cause hemolysis, which is the destruction of red blood cells. The baby may start to produce more red blood cells in an effort to replace the ones that were destroyed.

Risks

What are the causes and risks of the disease?

Rh incompatibility occurs when a woman who has Rh-negative blood and a man who has Rh-positive blood conceive a baby who is Rh positive.
There is generally no risk to the first baby, but rather to future babies who have Rh-positive blood. Previous abortions or stillbirths of an unborn child that had Rh-positive blood may present a risk to a woman who is Rh negative. This exposure to Rh-positive blood may be enough to cause her body to make antibodies to the Rh factor. Any future Rh-positive babies she may conceive may be at risk.

Prevention

What can be done to prevent the disease?

Rh incompatibility can be prevented by giving women an injection of something called Rho D immune globulin (i.e., RhoGAM). Rh-negative women who are candidates for this therapy include those who
  • are known to be carrying a baby that is Rh positive
  • have just given birth to an Rh-positive baby
  • have had a spontaneous abortion or elective abortion of a baby who was Rh positive
It is unclear exactly how Rho D immune globulin works. It is thought to prevent the woman from developing antibodies to the Rh factor. If a woman does not develop these antibodies, then there may be little risk to any future Rh-positive babies she may have.
This therapy may be given just before a woman delivers her Rh-positive baby or immediately afterward. Some women may be given it both times if the healthcare provider feels it is necessary.
This therapy is very effective in reducing the chances that a woman will have problems with future pregnancies. An Rh-negative woman should be tested for antibodies at the first prenatal visit, at 24 weeks, 28 weeks, 32 weeks, and 36 weeks of her pregnancy.
All Rh-positive women should be tested for antibodies if they have had blood transfusions, a baby with jaundice, a stillbirth, abortion, or problems with the placenta in the past.

Diagnosed

How is the disease diagnosed?

When diagnosing Rh incompatibility, a healthcare provider will obtain a full history of the mother. This should include her blood type and information about previous pregnancies and previous blood transfusions.
A blood test should be done to check the mother's blood type and to see if she has antibodies to the Rh factor. Also, the father should have a blood test done to determine his blood type and to see if he has the Rh factor.
Tests of the amniotic fluid, the fluid that surrounds the baby during pregnancy, can be done to see if there are Rh antibodies.
Tests that may be performed on a newborn include a test for Rh antibodies and a blood count from the cord blood. Scans to evaluate the function of the heart, liver, spleen, and brain may also be recommended.

Long Term Effects

What are the long-term effects of the disease?

The long-term effects of Rh incompatibility depend on whether the woman was given Rh immune globulin or any other treatment during the pregnancy.
When severe Rh incompatibility goes untreated, many infants die at a very early age. The infants that do survive may suffer from severe nerve problems including cerebral palsy and mental retardation.
Others may suffer from hydrops fetalis. Hydrops fetalis causes the destruction of large amounts of red blood cells. This leads to severe anemia, or low red blood cell count.
Also, these infants may have swelling of tissues and organs in the body that can lead to death. Kernicterus is another condition in which high levels of bilirubin build up in the brain. This can lead to brain damage.

Other Risks

What are the risks to others?

Rh incompatibility poses a high risk for future pregnancies and babies if left undiagnosed and untreated. However, with early prenatal care and appropriate therapy with Rho immune globulin, the risk to women and babies during future pregnancies is very low.

Treatments

What are the treatments for the disease?

The main treatment for Rh incompatibility is the Rho D immune globulin. It is given by injection to the mother at 28 weeks and at 72 hours after delivering a baby.
This injection may also be given after miscarriages, abortions or other terminated pregnancies.
This gamma globulin, also known as RhoGam, prevents the formation of antibodies that may affect other pregnancies.
Other procedures that may be necessary for treatment include:
  • planned delivery, via Cesarean birth or induced labor
  • phenobarbital given several weeks before delivery to lower the bilirubin level in the blood of the newborn
  • exchange transfusion, which is a blood transfusion in which fresh group 0, RH negative blood is given to an unborn baby in exchange for his or her blood
  • infusion of albumin, a protein, to decrease bilirubin levels
  • phototherapy, a procedure in which the newborn is placed under special lights, to help decrease the level of bilirubin in the blood
Depending on the degree of Rh incompatibility, the child may need physical therapy and a ventilator, or artificial breathing machine, for breathing difficulties.

Side Effects

What are the side effects of the treatments?

Side effects of medications include stomach upset, rash, and allergic reaction. Side effects of blood transfusions may include lethargy, muscle twitching, bleeding, and reaction to the blood being transfused. Many of the therapies may interfere with parent bonding. Encouraging parent bonding between treatments and making adjustments so parents can partake in care of their baby when possible will allow for more parent bonding.

After Treatment

What happens after treatment for the disease?

When the incompatibility is diagnosed and treated quickly, the infant usually recovers quickly without further problems.
Infants who developed more severe Rh reactions and are untreated may suffer severe nerve or brain damage, requiring life-long treatment with therapy to adjust to the world physically, mentally, and medically.

Monitor

How is the disease monitored?

The healthcare provider should be contacted if an infant who has been exposed to Rh incompatibility develops a fever, yellowing of the skin, poor appetite, poor weight gain, or inconsolable crying.

Sources

Harrison's Principles of Internal Medicine, Fauci et al, 1998

Complete Guide to Symptoms, Illness&Surgery, H. Griffith, M.D, 2000

Current Pediatric Diagnosis and Treatment, Hathaway, Hay, Groothuis, Paisley, 1993

Professional Guide to Diseases, Springhouse, 1995

Sagraves R, Letassy NA, Barton TL. Obstetrics. In: Young LY, Koda-Kimble MA, eds.Applied Therapeutics- The clinical use of drugs, 6th ed. Vancouver,Washington:Applied Therapeutics, Inc. 1995:44-20 to 44-22.

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