The people looking after you during your pregnancy need to know your blood group (type of blood) in case you ever need a blood transfusion. The screening test for blood group and red cell antibodies is very accurate. Sometimes you will need extra blood tests if antibodies are found.
This animation gives information on the screening tests you will be offered during pregnancy for you and your baby.
This test can be done with other blood tests, usually early in pregnancy. It is offered to you again on the 28th week of pregnancy.
What your blood group test result will tell you your blood group will be one of the following four main groups.
Within your blood group, you will either be D positive or D negative.
For example, your overall blood group might be written as ‘O RhD positive’.
Your blood is made up of:
These are found in a liquid called plasma. Your blood group is identified by antigens and antibodies contained in your blood.
Red blood cells sometimes have another antigen known as D antigen.
Red cell antibodies are part of your body's natural defence and fight against anything the body thinks is foreign. You may form antibodies if blood cells with a different blood group to yours, enter your blood stream. This can happen because of a blood transfusion or from your baby during pregnancy.
Red cell antibodies can pass from your bloodstream into your baby's blood, where anti-D antibodies may develop. Sometimes this can cause a rare condition called haemolytic disease of the fetus and newborn (HFDN), making your baby unwell. Babies with this rare condition usually need to be admitted to hospital.
If you are D negative, the cell free fetal DNA test can predict if:
This test will look at small amounts of your baby's DNA in your blood. DNA is the genetic information inside the body's cells. If you are D negative and your baby is D positive you will be offered anti-D immunoglobulin injections. This is referred to as anti-D in this information. This will greatly reduce HDFN developing.
Anti-D will help to stop antibodies being made if any f your baby's blood may have entered your blood stream, and so will reduce the chance of haemolytic disease of the newborn. Anti-D injections are made from plasma, which is the fluid part of blood that carries oxygen and blood cells around your body. The plasma used to make anti-D is collected from blood donors. You may need to be offered anti-D injections in future pregnancies.
Yes. Anti-D injections can cause some mild pain when they are injected into the muscle. Occasionally anti-D injections can cause allergic reactions. How it is produced is strictly controlled, so the risk of a known virus is being passed on to you from a donor is very low.
If you have this test, you will know your blood group and whether you are D positive or D negative.
It is less common to be D negative. If you are D negative, you will be offered a cell free fetal DNA test. If your baby is D negative, you would not be offered anti-D injections.
The test will also look for antibodies. It is important to know about these so that if you ever need a blood transfusion this could be given safely. Rarely, antibodies present in your blood carry a risk to your baby. If this happens you and your baby can be given specialist care.
Screening is a simple blood test. The only risk would be the same as having any blood test.
Contact your midwife or your hospital doctor (obstetrician) as soon as possible to remind them that you are D negative if you:
If any of these things happen, your body may start to produce antibodies and you may need an anti-D injection.
You should be offered an anti-D injection to reduce the risk of you producing antibodies.
This includes if: