Rh-negative Pregnancy

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Rh-ve pregnancy is a pregnancy in which the mother's blood group is Rh-ve and the baby's blood group is Rh+ve, inherited from the father. Its importance lies in the fact that this difference in the Rh factor can produce complications in the baby.

Also known as Rhesus incompatibility or Rhesus disease, it is one of the causes of hemolytic disease of the newborn (HDN / RhD Hemolytic Disease of the Newborn).

The Rhesus factor is a surface protein found on red blood cells. People who have this factor are said to be Rh positive while people who do not have this protein are said to be Rh negative.

The percentage of people who have the Rh factor is more than those who do not have this factor. In the United States, about 15 percent of the white population, 5 to 8 percent of the African-American and Hispanic populations, and 1 to 2 percent of the Asian and Native American populations are Rh-negative. (Marchofdimes.com).

The main problem with the Rh factor occurs when the blood of an Rh negative person comes in contact with the blood of an Rh positive person. This causes the Rh negative person to develop antibodies against the Rh factor. These antibodies never go away and the person is said to be sensitized against the Rh factor.

How Rh Sensitization Occurs in a Pregnant Woman

If an Rh negative woman becomes pregnant with an Rh positive baby (the baby can inherit the Rh factor from an Rh positive father), the baby's blood enters the mother's blood circulation sometime during the pregnancy, usually at around 28 weeks.

The mother's blood cells recognizes the foetal cells as foreign and produces Anti-Rh antibodies to destroy the cells. Her blood thus becomes sensitized against the Rh factor. When this sensitized blood carrying the antibodies re-enters the baby, it can attack the baby's blood cells causing them to break down. This can cause acute problems in the baby. The symptoms are usually more acute in the second baby which follows the first pregnancy, rather than in the baby which causes the sensitization.

The anti-Rh factors have no effect on the mother's cells, but can destroy the fetal red blood cells whenever they come in contact.

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Conditions in which Rh Sensitization can Occur

Some conditions can cause leakage of small amounts of fetal blood into the mother's blood circuation.

Signs and Symptoms of Rh-ve Pregnancy

Since it is the baby who is affected, there are no significant signs and symptoms in the mother.

Complications in the Fetus of an Rh-ve Pregnancy

The disease ranges from mild to severe.

  • Hydrops Fetalis : This is the most severe complication of Rh-ve pregnancy, where the baby suffers from widespread tissue damage. There is edema, enlarged liver and spleen and the baby may die in the uterus.

  • Icterus Gravis Neonatorum : This is the commonest type of complication, where the baby is not born jaundiced but develops jaundice within a few hours of childbirth. Exchange transfusion of the baby's blood should be done as early as possible to prevent brain damage by the circulating bilirubins.

  • Kernicterus : The high amount of bilirubin produced during the destruction of the fetal red blood cells may destroy the basal ganglia and the medulla of the baby's brain. The baby may develop convulsions, and be paralysed for life, if she survives.
  • Hemolytic Anaemia : The baby has anemia at birth due to destruction of RBC's. Blood Transfusion is necessary.

Management / Treatment of Rh-ve Pregnancy

During Pregnancy

  • A thorough history of previous childbirths, any family history of birth of jaundiced babies, or of stillbirths should be taken, since the first baby is usually normal but successive babies are affected.

  • Routine blood tests for investigation of the blood group. If the patient is Rh-ve, then the husband's blood group is checked. If both are Rh-ve, then the baby ia also Rh-ve and there is no fear of the baby being affected.

  • Indirect Coomb's test to detect Rh antibodies in the maternal blood is done at 20 weeks, 32 weeks and 36 weeks of pregnancy.

  • If Coomb's test is positive, then, Anti-Rh D immunoglobin is injected.

  • Anti- Rh D immunoglobin should be injected within 72 hours of every delivery and after every abortion - it is not necesary that Coomb's test should be done in all cases.

  • Many centers nowadays routinely inject Anti-Rh D immunoglobin at 28 weeks to prevent sensitization.

During Labor

  • Patient may be allowed to go in for a normal labor if the fetus has no complication.

  • Cesarian Section may be needed if the fetus is at risk or if normal labor is not possible.

  • The Pediatrician must be informed about the condition of the baby and all preparations must be made for her immediate treatment, if necessary.

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