Blood Test for Blood Type and Rh Status And Antibody Screen
There are 4 blood types, O, A, B, and AB, and each blood type can be Rh-positive or Rh-negative.
Most people are either A+ or O+ and the fewest are AB-
Approximate Distribution of Blood Types
Early in pregnancy a mother’s blood will be tested to determine the blood type Rh status – that is, whether she has the Rh (Rhesus) factor, in which case she is Rh-positive. (About 85 percent of Caucasians are Rh-positive, as are 90 to 95 percent of African Americans and 98 to 99 percent of Asian Americans). If you don’t have it, you’re Rh-negative, and you’ll need to take certain precautions during your pregnancy.
If a pregnant woman is Rh-negative, then there is a chance she might get sensitized during pregnancy or delivery, which could be a problem in the next pregnancy. Women who are Rh-sensitized can create antibodies which could conceivably cross the placenta and attack the fetus’ red cells.
To prevent Rh-sensitization, pregnant Rh-negative women get a shot of Rh iimmunoglobulin at least once during the pregnancy, as well as after delivery if the baby turns out to be Rh-positive.
This shot will protect the mother from developing antibodies that could be dangerous during this pregnancy or in future pregnancies. If the baby’s father is also Rh-negative, then the baby will be Rh-negative too, and no shot is needed.
You could also have these antibodies under the following circumstances:
- A previous miscarriage
- A previous abortion
- A previous pregnancy and delivery
- An ectopic pregnanc
If there are antibodies, then it’s too late to get the shot, and if the baby is Rh-positive, he’s likely to have some problems. If you don’t have the antibodies, then the shot will protect you from developing them.
Type and screen
Blood typing is a laboratory test that identifies blood group antigens (substances that stimulate an immune response) belonging to the ABO blood group system. The test classifies blood into four groups designated A, B, AB, and O. Antibody screening is a test to detect atypical antibodies in the serum that may have been formed as a result of transfusion or pregnancy. An antibody is a protein produced by lymphocytes (nongranular white blood cells) that binds to an antigen, facilitating its removal by phagocytosis (or engulfing by macrophages) or lysis (cell rupture or decomposition). The type and screen (T&S) is performed on persons who may need a transfusion of blood products. These tests are followed by the compatibility test (cross-match). This test insures that no antibodies are detected in the recipient's serum that will react with the donor's red blood cells.
Blood typing and screening are most commonly performed to ensure that a person who needs a transfusion will receive blood that matches (is compatible with) his or her own; and that clinically significant antibodies are identified if present. People must receive blood of the same blood type; otherwise, a severe transfusion reaction may result.
Parents who are expecting a baby have their blood typed to diagnose and prevent hemolytic disease of the newborn (HDN), a type of anemia also known as erythroblastosis fetalis. Babies who have a blood type different from their mother's are at risk for developing this disease.
Determination of paternity
A child inherits factors or genes from each parent that determine his or her blood type. This fact makes blood typing useful in paternity testing. The blood types of the child, mother, and alleged father are compared to determine paternity.
Legal investigations may require typing of blood or such other body fluids as semen or saliva to identify criminal suspects. In some cases typing is used to identify the victims of crime or major disasters.
Blood typing and screening tests are performed in a blood bank laboratory by technologists trained in blood bank and transfusion services. The tests are performed on blood after it has been separated into cells and serum (the yellow liquid left after the blood cells are removed). Costs for both tests are covered by insurance when the tests are determined to be medically necessary.
Blood bank laboratories are usually located in blood center facilities, such as those operated by the American Red Cross, that collect, process, and supply blood that is donated. Blood bank laboratories are also found in most hospitals and other facilities that prepare blood for transfusion. These laboratories are regulated by the United States Food and Drug Administration (FDA) and are inspected and accredited by a professional association such as the American Association of Blood Banks (AABB).
Blood typing and screening tests are based on the reaction between antigens and antibodies. An antigen can be anything that triggers the body's immune response. The body produces a special protein called an antibody that has a uniquely shaped site that combines with the antigen to neutralize it. A person's body normally does not produce antibodies against its own antigens.
The antigens found on the surface of red blood cells are important because they determine a person's blood type. When red blood cells having a certain blood type antigen are mixed with serum containing antibodies against that antigen, the antibodies combine with and stick to the antigen. In a test tube, this reaction is visible as clumping or aggregating.
Although there are over 600 known red blood cell antigens organized into 22 blood group systems, routine blood typing is usually concerned with only two systems: the ABO and Rh blood group systems. Antibody screening helps to identify antibodies against several other groups of red blood cell antigens.
THE ABO BLOOD GROUP SYSTEM. In 1901, Karl Landsteiner, an Austrian pathologist, randomly combined the serum and red blood cells of his colleagues. From the reactions he observed in test tubes, he developed the ABO blood group system. This discovery earned him the 1930 Nobel Prize in Medicine. A person's ABO blood type—A, B, AB, or O—is based on the presence or absence of the A and B antigens on his red blood cells. The A blood type has only the A antigen and the B blood type has only the B antigen. The AB blood type has both A and B antigens, and the O blood type has neither the A nor the B antigen.
By the time a person is six months old, he or she will have developed antibodies against the antigens that his or her red blood cells lack. That is, a person with A blood type will have anti-B antibodies, and a person with B blood type will have anti-A antibodies. A person with AB blood type will have neither antibody, but a person with O blood type will have both anti-A and anti-B antibodies. Although the distribution of each of the four ABO blood types varies among racial groups, O is the most common and AB is the least common in all groups.
FORWARD AND REVERSE TYPING. ABO typing is the first test done on blood when it is tested for transfusion. A person must receive ABO-matched blood because ABO incompatibilities are the major cause of fatal transfusion reactions. To guard against these incompatibilities, typing is done in two steps. In the first step, called forward typing, the patient's blood is mixed with serum that contains antibodies against type A blood, then with serum that contains antibodies against type B blood. A determination of the blood type is based on whether or not the blood clots in the presence of these sera.
In reverse typing, the patient's blood serum is mixed with blood that is known to be type A and type B. Again, the presence of clotting is used to determine the type.
An ABO incompatibility between a pregnant woman and her baby is a common cause of HDN but seldom requires treatment. This is because the majority of ABO antibodies are IgM, which are too large to cross the placenta. It is the IgG component that may cause HDN, and this is most often present in the plasma of group O mothers.
Paternity testing compares the ABO blood types of the child, mother, and alleged father. The alleged father cannot be the biological father if the child's blood type requires a gene that neither he nor the mother have. For example, a child with blood type B whose mother has blood type O requires a father with either AB or B blood type; a man with blood type O cannot be the biological father.
In some people, ABO antigens can be detected in body fluids other than blood, such as saliva, sweat, or semen. People whose body fluids contain detectable amounts of antigens are known as secretors. ABO typing of these fluids provides clues in legal investigations.
THE RH BLOOD GROUP SYSTEM. The Rh, or Rhesus, system was first detected in 1940 by Landsteiner and Wiener when they injected blood from rhesus monkeys into guinea pigs and rabbits. More than 50 antigens have since been discovered that belong to this system, making it the most complex red blood cell antigen system.
In routine blood typing and cross-matching tests, only one of these 50 antigens, the D antigen, also known as the Rh factor or Rh o [D], is tested for. If the D antigen is present, that person is Rh-positive; if the D antigen is absent, that person is Rh-negative.
Other important antigens in the Rh system are C, c, E, and e. These antigens are not usually tested for in routine blood typing tests. Testing for the presence of these antigens, however, is useful in paternity testing, and in cases in which a technologist screens blood to identify unexpected Rh antibodies or find matching blood for a person with antibodies to one or more of these antigens.
Unlike the ABO system, antibodies to Rh antigens don't develop naturally. They develop only as an immune response after a transfusion or during pregnancy. The incidence of the Rh blood types varies between
The distribution of ABO and Rh blood groups in the overall United States population is as follows:
In transfusions, the Rh system is next in importance after the ABO system. Most Rh-negative people who receive Rh-positive blood will develop anti-D antibodies. A later transfusion of Rh-positive blood may result in a severe or fatal transfusion reaction.
Rh incompatibility is the most common and severe cause of HDN. This incompatibility may occur when an Rh-negative mother and an Rh-positive father have an Rh-positive baby. Cells from the baby can cross the placenta and enter the mother's bloodstream, causing the mother to make anti-D antibodies. Unlike ABO antibodies, the structure of anti-D antibodies makes it likely that they will cross the placenta and enter the baby's bloodstream. There, they can destroy the baby's red blood cells, causing a severe or fatal anemia.
The first step in preventing HDN is to find out the Rh types of the expectant parents. If the mother is Rhnegative and the father is Rh-positive, the baby is at risk for developing HDN. The next step is performing an antibody screen of the mother's serum to make sure she doesn't already have anti-D antibodies from a previous pregnancy or transfusion. Finally, the Rh-negative mother is given an injection of Rh immunoglobulin (RhIg) at 28 weeks of gestation and again after delivery, if the baby is Rh positive. The RhIg attaches to any Rh-positive cells from the baby in the mother's bloodstream, preventing them from triggering anti-D antibody production in the mother. An Rh-negative woman
B-Negative Blood Type: How It Affects Your Pregnancy
A woman’s blood type and Rh factor can impact her pregnancy. That’s why every pregnant woman will have an Rh factor test. In some cases, the father of the baby will be tested too. Here’s what you need to know about blood types and Rh factor.
The four major blood types are:
Which classification you are is determined by antigens (proteins) on the surface of blood cells that trigger an immune response.
According to the American Pregnancy Association, the Rh factor is a specific type of protein on the surface of red blood cells. If your blood has these proteins, it’s considered Rh positive. This is the most common blood type.
If you don’t have these proteins, you are Rh negative. Being Rh negative is not considered an illness, and it doesn’t usually impact your health.
But it can be problematic during pregnancy.
If you are Rh negative and the father of your baby is Rh positive, your baby might inherit the Rh-positive gene. Stanford Children’s Health explains that the Rh-positive gene is dominant. So even when it’s paired with an Rh-negative gene, the positive gene is dominant. If both parents are Rh negative, the baby will be Rh negative too.
Rh Factor Complications
Complications can occur when the mother’s Rh factor is negative and her baby’s Rh factor is positive.
According to the Mayo Clinic, small amounts of your blood can come into contact with your baby’s blood during delivery or other times during your pregnancy, including:
- Amniocentesis, a prenatal test that involves retrieving a sample of the amniotic fluid in your uterus
- Chorionic villus sampling, a prenatal test that involves retrieving a sample of the placenta
- Fetal blood sample
- Bleeding during your pregnancy
- Ectopic pregnancy, when the fertilized egg implants somewhere other than the uterus, often in one of the fallopian tubes
If both mother and baby are Rh positive, compatibility isn’t an issue. But if the mother is Rh negative and the baby is Rh positive, the mother’s body may respond with an allergic reaction to the blood of the baby.
The mother may produce proteins called Rh antibodies. According to the American Congress of Obstetrics and Gynecologists (ACOG), someone with Rh-negative blood who produces Rh antibodies is considered “Rh sensitized.”
This isn’t normally a concern with the first pregnancy, because in many instances the baby is born before the mother’s body can develop a significant amount of antibodies. But without treatment during the first pregnancy, it can be an issue with any pregnancies that follow.
If your next baby is also Rh positive, your body will produce the Rh antibodies again. This time, they can cross the placenta and attack your baby’s red blood cells. Without enough red blood cells, your baby won’t get enough oxygen. This condition is known as hemolytic disease or hemolytic anemia. It can lead to illness, brain damage, and even death to your baby before or after delivery.
It’s very important to prevent your body from producing these antibodies. Otherwise, every Rh-positive baby you carry after the first pregnancy could be at risk for this condition.
Rh Factor Antibody Screen
Women who test negative for the Rh factor early in their pregnancy may need a second blood test, or antibody screen, in or around week 28.
The antibody screen tests for the presence of antibodies in Rh-positive blood. If no Rh antibodies can be detected, an injection of Rh immunoglobulin (Rhlg) will be administered. This prevents a woman’s body from producing Rh antibodies during her pregnancy.
If you test positive for the presence of Rh antibodies, the injection won’t be effective. Instead, your baby will be closely monitored throughout your pregnancy.
In severe cases of anemia, ACOG cautions that it may be necessary to delivery your baby before 37 weeks. A blood transfusion may be necessary immediately after delivery or through the umbilical cord while the baby is still in your uterus. If anemia is present but mild, it may be possible to deliver your baby at full term.
If a baby is born with Rh-positive blood, the mother will receive another injection of Rhlg within 72 hours after delivery.
If you or your baby’s father test positive for the Rh factor, it’s important to take certain precautions during your pregnancy. Contact your doctor immediately if you experience vaginal bleeding.
The Mayo Clinic recommends scheduling an Rhlg injection with your doctor. It’s also important to inform the doctors and nurses assisting you during labor and delivery if you and your baby are not Rh compatible.
Rh Factor in Pregnancy
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For roughly 10 percent of pregnant women, knowing your Rh factor can be a matter of life or death for your baby or for your future unborn babies!
Ninety percent of people have Rh-positive blood, and therefore have no need to worry about Rh factor disease.
But women who have Rh-negative blood must be managed properly during pregnancy and postpartum to prevent potentially devastating future consequences.
The Rh (Rhesus) factor is a genetic trait that determines whether a certain protein is found on the surface of your red blood cells.
If you have this protein, you are Rh positive. If you do not have it, you are Rh negative. Whether you are Rh positive or negative doesn’t matter in the ordinary course of your life, as it does not affect your health.
It can affect your pregnancy, however, if your Rh factor is negative and your unborn baby is Rh positive. This condition is known as Rh incompatibility.
The baby’s blood type is inherited from the mother and father. An Rh-negative parent can only pass on an Rh-negative blood type to his or her offspring.
An Rh-positive parent, however, can pass on either an Rh positive or an Rh-negative blood type, depending on that person’s DNA.
Thus, if both parents of the baby are Rh negative, the baby will always be Rh negative. If the father is Rh positive and the mother is Rh negative, the baby usually will be born Rh positive, resulting in Rh-incompatibility.
This condition has the potential to create Rh sensitization in the mother, a very undesirable development (see below).
In most cases complications do not arise since this condition is usually diagnosed early in pregnancy and treated with a blood product called Rh immunoglobulin (a well-known version of this is called RhoGAM).
This is given as a one-time injection. Rh immuno-globulin prevents your immune system from making antibodies that can attack your baby’s blood during pregnancy.
During pregnancy (rarely), but typically during delivery, there is a chance that some of your baby’s red blood cells will mix with your blood.
If you are Rh negative and your baby is Rh positive, your body may respond by producing antibodies that attack the Rh-positive red blood cells.
This process is called Rh sensitization.
In most cases this isn’t a problem if it’s your first pregnancy, since the number of antibodies produced initially isn’t enough to harm the baby, and because the sensitization occurs after the baby has delivered.
If you do not receive the Rh immunoglobulin treatment, however, your body may continue producing antibodies against Rh-positive blood for the rest of your life. (Interestingly, this only happens in about 15 percent of pregnancies thus exposed).
If you become pregnant a second time and the fetus has Rh-positive blood again, these antibodies can cross the placenta and attack the fetal red blood cells.
This leads to a steady loss of blood in the fetus as the fetal red blood cells attacked by these Rh antibodies are removed from the fetal circulation. This can cause fetal anemia, and possibly lead to a severe condition called fetal hydrops, or hydrops fetalis.
Hydrops fetalis is a potentially fatal consequence of Rh incompatibility. The severe fetal anemia causes the heart to work extremely hard to circulate fetal blood. Eventually the heart swells and goes into heart failure.
This causes severe edema (swelling) in the baby’s entire body, creating what is called a hydropic fetus.
There are other conditions that can cause fetal hydrops, such as fetal heart defects or viral infections of the fetus during pregnancy (such as Parvovirus B19). Those are referred to as non-immune hydrops.
If fetal anemia is detected during pregnancy, specialists have the ability to perform a fetal blood transfusion during the pregnancy. Fortunately, due to the widespread use of Rh immunoglobulin, this is rarely necessary.
Common findings associated with Rh incompatibility include:
- Excessive amniotic fluid surrounding the unborn infant (diagnosed by fetal ultrasound)
- Poor muscle tone in the infant after it is born
- Delayed motor and mental development
- Prolonged jaundice
The Rh Factor Blood Test
If you are pregnant, your healthcare provider is required BY LAW to test your blood type and Rh factor early in the pregnancy.
Every woman should know her blood type! This basic blood test determines whether you are Rh positive or negative. There are no risks involved with this test, nor do you need any special preparation.
If you are Rh negative, then commonly the father of the baby is also tested. If you and the father both test Rh negative, your baby will be Rh negative and there is no cause for concern.
Likewise, if you and the father both test Rh positive, the baby will also be Rh positive. Another routine pregnancy blood test called an antibody screen is performed in order to make sure that you are not already Rh-sensitized.
Some OB doctors are so risk-averse that they will provide Rh antibody treatment to an Rh-negative pregnant woman regardless of the father’s blood type.
One rationale for this is the remote chance that the lab made an error on the father’s blood type. Another is that occasionally the woman’s “partner” is not the actual father of the baby!
There is a controversial new blood test for Rh-negative pregnant women called the fetal D antigen test. During the pregnancy, the mother’s blood can be tested for the presence or absence of fetal Rh DNA, known as the D antigen DNA.
If this test shows no D antigen DNA present in the mother’s blood, the assumption is that the baby must be Rh negative and therefore the pregnant woman does not need any Rh immunoglobulin.
Relying on this result and failing to administer Rh immunoglobulin could be thought of as “betting your baby’s life” on the results of this one test, however, and many OB doctors are unwilling to do that.
If you are Rh negative, you will need an Rh immunoglobulin injection about the 28 th week of pregnancy (earlier for twins).
The antibody screen will be repeated before administering the Rh immunoglobulin medicine to confirm that you have not become Rh sensitized.
After you receive this medicine, the antibody screen can remain positive for the rest of your pregnancy because it will detect the medicine that you received.
The Rh immunoglobulin injection, also known as RhIG (RhoGAM is the most well-known but there are others), is typically given around the 28 th week of pregnancy and usually again after delivery, within 72 hours.
After your baby is born, his or her blood type is tested. If the baby is Rh positive, you get the shot. If the baby is Rh negative, no shot!
Not only does the immunoglobulin prevent the mother’s immune system from producing antibodies to Rh-positive blood, it also destroys any red blood cells from the fetus that may have entered her system before her body began developing the antibodies.
Being Rh Negative
During pregnancy, any time your baby’s blood can potentially come into contact with your Rh-negative blood, you’ll need to take steps to ensure your safety. For any of the following situations, you may need an extra treatment of Rh immunoglobulin.
Situations in which this may occur include:
- Bleeding during pregnancy
- Ectopic pregnancy
- Molar pregnancy
- Amniocentesis or Chorionic Villous Sampling (CVS)
- Lack of prenatal care
- Placenta previa with bleeding
- Placental abruption with bleeding
- In utero fetal death
- Trauma, especially blunt force, to abdomen during pregnancy, like with a car accident or serious fall
Http://www. babymed. com/pregnancy-test/blood-test-blood-type-and-rh-status-and-antibody-screen
Http://www. surgeryencyclopedia. com/St-Wr/Type-and-Screen. html
Http://www. healthline. com/health/pregnancy/b-negative-blood-type
Http://www. pregnancycorner. com/being-pregnant/complications/rh-factor. html