The Antibody Tests at 28 Weeks Pregnant

Page content

What is an Antibody?

An antibody is a chemical produced by the white blood cells of the body. It is also known as an immunoglobulin. There are 5 main immunoglobulins called IgA, IgM, IgD, IgG, and IgE. Antibodies are produced in the presence of foreign objects into the body. The antibody will bind to the foreign object called an antigen. They are produced specifically for an antigen that enters the body. When the antibodies are produced, it triggers other cells of the immune system to attack and they will engulf and destroy the foreign cells covered in antibody.

However in autoimmune diseases the body can produce antibodies against its own cells. This still triggers the immune system to destroy its own cells. In these cases, the immune system will need to be suppressed, or a bone marrow transplant performed.

Why Is the Test Completed?

The antibody tests at 28 weeks pregnant are used to determine if the pregnant woman has antibodies to her baby’s blood. If a baby has inherited a positive Rh factor from its father, and the mother has a negative Rh factor, then the pregnant woman will develop antibodies towards the baby’s red blood cells.

This test is also completed to determine if a mother has developed antibodies to the baby’s blood if the blood type is different.

The tests may be also recommended by a physician if the pregnant woman has previously had a blood transfusion, or if this is not her first pregnancy. A previous pregnancy might have triggered an antibody response that worsens in a subsequent pregnancy.

The Test & What Do The Results Mean

This antibody tests at 28 weeks pregnant are performed by drawing a sample of the pregnant woman’s blood and testing it for the presence of antibodies.

If the presence of antibodies are discovered during the test this will mean that the baby may be in danger if the mother is producing antibodies to its red blood cells. If the presence of antibodies is detected, the physician will also test the father’s blood to determine if the baby has inherited his blood type. The physician will also test if the father’s blood will react to the mother’s blood. If this reaction happens, then the physician will have to monitor the pregnant woman, as the reaction is a sign that the mother’s blood may have a reaction to baby’s blood. This may result in a medical condition called hemolytic disease of the newborn. In this disease the baby’s red blood cells are destroyed and if this is the first pregnancy for a mother who has a negative RH factor, this baby may not be affected. However, the woman will need to be given a positive immunoglobulin injection at 28 weeks during her next pregnancy if she previously had antibodies present during her last pregnancy.


Web Source: American Association for Clinical Chemistry. “First Trimester Antibody Screen.” 2010. Available:

Web Source: Women’s Healthcare Topics. “Pregnancy Week by Week - 28 Weeks Pregnant.” 2010. Available: