Rh Incompatibility & Isoimmunization during pregnancy

Dr Ashwini Anil Kumar Sirapanasetty *

What’s an Rh Factor?

An Rh factor is a protein found on some red blood cells (RBCs). Not everyone carries this protein, though most do. They are Rh-positive. People who don't carry the protein are Rh-negative.

What is Rh incompatibility?

When a mother-to-be and father-to-be are not both positive or negative for Rh factor, it's called Rh incompatibility.

For example:
If a woman who is Rh negative and a man who is Rh positive conceive a baby, the fetus may have Rh-positive blood, inherited from the father. (About half of the children born to an Rh-negative mother and Rh-positive father will be Rh-positive.)

Rh incompatibility usually isn't a problem if it's the mother's first pregnancy. That's because the baby's blood does not normally enter the mother's circulatory system during the pregnancy.

During the birth, though, the mother's and baby's blood can mix. If this happens, the mother's body recognises the Rh protein as a foreign substance. It then might begin making antibodies (proteins that act as protectors if foreign cells enter the body) against the Rh protein.

Rh-negative pregnant women can be exposed to the Rh protein that might cause antibody production in other ways too. These include: blood transfusions with Rh-positive blood miscarriage ectopic pregnancy

What is Isoimmunization?

Isoimmunization (Sometimes called Rh sensitisation, haemolytic disease of the fetus, Rh incompatibility). A condition that happens when a pregnant woman's blood protein is incompatible with the baby's, causing her immune system to react and destroy the baby's blood cells.

What Causes Isoimmunization?

When the proteins on the surface of the baby's red blood cells are different from the mother's protein, the mother's immune system produces antibodies that fight and destroy the baby's cells. Red cell destruction can make the baby anaemic well before birth. Although the Rh(D) protein is the most common one, several other proteins can cause this problem, including among proteins KELL, Kidd, Duffy, and others.

When is a baby at Risk ?

Rh antibodies are harmless until the mother's second or later pregnancies. If she is ever carrying another Rh-positive child, her Rh antibodies will recognise the Rh proteins on the surface of the baby's blood cells as foreign.

Her antibodies will pass into the baby's bloodstream and attack those cells.This can make the baby's red blood cells swell and rupture. This is known as haemolytic or Rh disease of the newborn. It can make a baby's blood count get very low.

What are the symptoms of Rh incompatibility?

Rh incompatibility symptoms in your unborn baby can range from mild to life-threatening. When your antibodies attack your baby’s red blood cells, haemolytic disease can occur. This means your baby’s red blood cells are destroyed. When your baby’s healthy red blood cells are destroyed, bilirubin will build up in their bloodstream.

Bilirubin is a chemical that’s created from the breakdown of red blood cells. Too much bilirubin is a sign that the liver (HYPERBILIRUBINEMIA), which is responsible for processing old blood cells, is having trouble.

Your baby may have one or more of the following symptoms if their bilirubin levels are high after birth : jaundice, a yellowing of the skin and whites of the eyes(severity May lead to cerebral palsy) lethargy low muscle tone brain damage to the baby, which is known as kernicterus fluid buildup or swelling in the baby trouble with mental function, movement, hearing, and speech seizures anaemia heart failure.

These symptoms will subside after completing treatment for the Rh incompatibility.

How is Rh incompatibility diagnosed?

A blood test to determine your Rh status will likely be done at your first prenatal visit with your doctor.If you’re Rh-negative, your partner may also be tested. If your partner is also Rh-negative, you don’t have anything to worry about. If your partner is Rh-positive and you’re Rh-negative, your doctor will look for the following signs of Rh incompatibility.

A positive indirect Coombstest is a sign of Rh incompatibility. This test uses a blood sample to look for the presence of cell-destroying antibodies within the plasma of your blood.Higher-than-normal levels of bilirubin in your infant’s blood is a sign of Rh incompatibility.

In a full-term baby who is less than 24 hours old, the levels of bilirubin should be less than 6.0 milligrams per deciliter.Signs of red blood cell destruction in your infant’s blood may indicate Rh incompatibility.

This can be determined by the shape and structure of the red blood cells when examined under a microscope.Your doctor can test your baby’s blood for the presence of maternal antibodies that are breaking down the red blood cells.

How is Rh incompatibility treated ?

If a pregnant woman has the potential to develop Rh incompatibility, doctors give her a series of two Rh immune-globulin shots during her first pregnancy. She'll get: the first shot around the 28th week of pregnancy the second shot within 72 hours of giving birth.

Rh immune-globulin acts like a vaccine. It prevents the mother's body from making any Rh antibodies that could cause serious health problems in the newborn or affect a future pregnancy.A woman also might get a dose of Rh immune-globulin if she has a miscarriage, an amniocentesis, or any bleeding during pregnancy.

If a doctor finds that a woman has already developed Rh antibodies, her pregnancy will be closely watched to make sure that those levels are not too high.In rare cases, if the incompatibility is severe and a baby is in danger, the baby can get special blood transfusions called exchange transfusions either before birth (intrauterine fetal transfusions) or after delivery.

Exchange transfusions replace the baby's blood with blood with Rh-negative blood cells. This stabilises the level of red blood cells and minimises damage from Rh antibodies already in the baby's bloodstream.

Can Rh incompatibility be prevented?

This condition is preventable. If you think you may be pregnant and have an Rh-negative blood type, you should talk with your doctor to determine the best plan. If the father of your child is Rh-positive or his blood type is unknown, receiving preventive treatment with immune globulins will prevent serious effects.