Table of ContentsView AllTable of ContentsRh Factor in PregnancyRh Factor of Each ParentRh IncompatibilityPreventive InjectionTransfusion and Rh FactorCommunicating Rh FactorFetal Health
Table of ContentsView All
View All
Table of Contents
Rh Factor in Pregnancy
Rh Factor of Each Parent
Rh Incompatibility
Preventive Injection
Transfusion and Rh Factor
Communicating Rh Factor
Fetal Health
Blood typingincludes the identification of A and B sugarantigensand Rh proteins on the surface of the red blood cells (RBCs). The presence or absence of Rh proteins on red blood cells is used when describing a blood type as positive (+) or negative (-).
Your Rh type has no general effect on your health. It only becomes important during pregnancy or when you need a blood transfusion. Pregnant people who are Rh negative must take precautions against developing anti-Rh antibodies, which can affect the health of future pregnancies.
This article will describe what Rh factor is, when it matters, and what you should do if you find out that you are Rh negative or Rh positive, especially during pregnancy.
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Rh Factor: Meaning of Blood Type in Pregnancy
Normally, blood testing is part of early prenatal care. Blood testing during the first trimester of pregnancy includes blood typing,RBC count, white blood cell (WBC) count, platelet count, andelectrolyte levels.
Rh incompatibilitycan complicate pregnancy for an Rh negative pregnant person who is carrying an Rh positive fetus. It does not affect pregnancy if the pregnant person is Rh positive, regardless of the Rh type of the fetus.
Blood from an Rh positive fetus can enter the bloodstream of the pregnant person and stimulate the production of anti-Rh antibodies. This is calledRh sensitization. In a future pregnancy, these antibodies can attack the blood cells of an Rh positive fetus.
What Are Antibodies?Antibodies are immune proteins that form in response to antigen exposure. Antigens are proteins or other substances that are not part of your body’s own structure. Common antigens your body is exposed to include those found on viruses and bacteria.If you are exposed to someone else’s blood (such as a blood transfusion or from a fetus during pregnancy), your body would recognize Rh proteins as antigens if your own RBCs don’t have these proteins.You would form antibodies to destroy RBCs that are Rh positive. It takes weeks to months for these antibodies to develop. These antibodies can cross the placenta in pregnancy and harm an Rh positive fetus.
What Are Antibodies?
Antibodies are immune proteins that form in response to antigen exposure. Antigens are proteins or other substances that are not part of your body’s own structure. Common antigens your body is exposed to include those found on viruses and bacteria.If you are exposed to someone else’s blood (such as a blood transfusion or from a fetus during pregnancy), your body would recognize Rh proteins as antigens if your own RBCs don’t have these proteins.You would form antibodies to destroy RBCs that are Rh positive. It takes weeks to months for these antibodies to develop. These antibodies can cross the placenta in pregnancy and harm an Rh positive fetus.
Antibodies are immune proteins that form in response to antigen exposure. Antigens are proteins or other substances that are not part of your body’s own structure. Common antigens your body is exposed to include those found on viruses and bacteria.
If you are exposed to someone else’s blood (such as a blood transfusion or from a fetus during pregnancy), your body would recognize Rh proteins as antigens if your own RBCs don’t have these proteins.You would form antibodies to destroy RBCs that are Rh positive. It takes weeks to months for these antibodies to develop. These antibodies can cross the placenta in pregnancy and harm an Rh positive fetus.
Each person has two genes for Rh factor. If one or both of those genes code for being Rh positive, they are Rh positive. If both of their genes code for being Rh negative, they are Rh negative.
If both of their genes code for being Rh positive, all of their genetic offspring will be Rh positive, regardless of the Rh type of the other genetic parent.
If a person is pregnant with a fetus conceived with their own egg and the sperm of the other genetic parent, Rh factor can affect the pregnancy in these ways:
If the pregnant person is carrying a fetus conceived with another person’s egg throughin vitro fertilization(such as in surrogacy or egg donation), Rh factor can affect the pregnancy in these ways:
Rh Factor Incompatibility, Antibodies, and Fetus Risks
Blood typing is important during pregnancy because Rh incompatibility can lead to serious problems for the fetus. Rh incompatibility means that the pregnant person is Rh negative, and the fetus is Rh positive.
The survival of a hemolytic reaction due to Rh incompatibility is variable. Fetuses and babies who experience mild anemia can survive if treatment is initiated early, but many can develop lifelong disability or might not survive if the reaction is severe.
When Do Rh Antibodies Form?
A pregnant person who is Rh negative may produce antibodies (immune proteins) against the Rh proteins on the fetus’s red blood cells. Most often, the fetus’s blood doesn’t mix with the pregnant person’s blood until labor and delivery.
However, anti-Rh antibody formation can occur afteramniocentesisand other invasive prenatal testing procedures. A person may also form Rh antibodies due toectopic pregnancy, miscarriage, or pregnancy termination if there is Rh incompatibility.
Antibody formation after the first exposure to Rh factor takes time, so it usually doesn’t affect the pregnancy in which the sensitization occurs. Also, Rh factor doesn’t develop on the fetus’s red blood cells before eight weeks of pregnancy, so early pregnancy loss or termination is less of a risk.
Blood transfusions are given after blood is typed and crossmatched to ensure there is no Rh incompatibility. In an emergency, when there is no time for blood typing,type O Rh negative bloodis given.Therefore, blood transfusion is a very rare reason a person would form Rh antibodies.
Incompatible Rh Factor Injection and Future Pregnancies
Preventing Anti-Rh Antibody Formation
Use of RhoGamIf a person with Rh antibodies becomes pregnant with an Rh positive fetus, the already-formed antibodies can quickly attack the fetus’s blood, causing severe hemolysis. Therefore, prevention of antibody formation is used during a first pregnancy or at the time of a miscarriage or pregnancy termination.
Use of RhoGam
If a person with Rh antibodies becomes pregnant with an Rh positive fetus, the already-formed antibodies can quickly attack the fetus’s blood, causing severe hemolysis. Therefore, prevention of antibody formation is used during a first pregnancy or at the time of a miscarriage or pregnancy termination.
When Rh Antibodies are Present
Transfusions and Rh Negative Blood
When donor blood is used for a blood transfusion, it istyped and matched for compatibility. This includes matching the Rh type and A, B, AB, and O blood types (the ABO system).
If a person is Rh negative and needs a blood transfusion, the donor blood used in a transfusion must be Rh negative and of a compatible ABO type.
If an Rh negative person receives an Rh positive blood transfusion, the effect depends on whether they have been exposed and sensitized before. If they don’t have Rh antibodies already, the transfusion will not affect them immediately, but they may develop Rh antibodies.
Once a person has Rh antibodies, future transfusions of Rh positive blood may result in a hemolytic transfusion reaction in the person and can affect a pregnancy with an Rh positive fetus.You can donate blood if you are Rh positive or Rh negative. Your blood would be typed and only given to recipients who would not be at risk of rejecting your blood during a blood transfusion.
The O negative blood type is considered auniversal donorthat would not be rejected recipients of any blood type.This type is used in emergency situations when there is not enough time to type the blood transfusion recipient for a match. The AB-positive blood type is considered a universal recipient who may receive blood of any type.
The ABO type must also be considered when giving a person a transfusion. If you are type A, you will have anti-B antibodies from early in life (without exposure to blood), and If you are type B, you will have anti-A antibodies.A type O person has both anti-A and anti-B antibodies, while a type AB person has neither of these.
If you are given a blood transfusion that is positive for the A and/or B proteins to which you have an antibody, a severe immune response will occur, with a potentially deadly hemolytic reaction.
Why Do People Need Blood Transfusions?
Communicating Rh Factor Status During Pregnancy
If you are pregnant, you can expect to have Rh typing during the first trimester of your pregnancy. If you are Rh positive, no action needs to be taken. If you are Rh negative, you may need treatment to prevent your body from making Rh antibodies.
Antibodies that form in the first Rh incompatible pregnancy are not likely to cause a severe reaction during that pregnancy. Sensitization usually occurs during labor and delivery. Also, these first antibodies made are of the large IgM (immunoglobulin M) type that can’t pass through the placenta to harm the fetus.
However, for subsequent pregnancies after being sensitized, the pregnant person’s body is poised to make anti-Rh antibodies of the IgG (immunoglobulin G) type, which are smaller and can pass through the placenta to enter the fetus’s bloodstream. During a subsequent pregnancy, the antibodies can attack an Rh positive fetus’s RBCs.
Future Health of Babies in Rh Incompatible Pregnancies
With the use of screening tests and the Rho(D) immune globulin shot, fewer Rh negative pregnant people develop anti-Rh antibodies that can affect future pregnancies.If they have developed an antibody, the health of the fetus will be closely monitored to look for signs of Rh incompatibility and the development ofhemolytic disease of the fetus and newborn.
These steps can help prevent some of the severe consequences of hemolysis, such ashydrops(fluid throughout the body tissues), which can be fatal.Other effects can be an enlarged liver orkernicterus, in which there is brain damage due to high bilirubin.
Summary
Blood type is defined as positive or negative based on whether the Rh factor is present on the surface of the RBCs. Most people are Rh positive, but a significant minority are Rh negative.
Blood typing is important before a blood transfusion and as part of prenatal care. A person who is Rh negative should not receive Rh positive blood, but a person who is Rh positive can receive Rh positive or Rh negative blood.
Rh incompatibility occurs when an Rh negative pregnant person is carrying an Rh positive fetus. The fetal blood can mix with the pregnant person’s and induce the formation of anti-Rh antibodies. This most often occurs during labor and delivery but may happen earlier in pregnancy, including lost or terminated pregnancies and during certain procedures. These antibodies can destroy fetal Rh positive RBCs in future pregnancies.
If there’s a risk of Rh incompatibility, a pregnant person can be treated with RhoGAM medication to prevent the formation of anti-Rh antibodies. If these antibodies have developed, a subsequent pregnancy with Rh incompatibility carries a high risk of severe health consequences for the fetus.
What Is the Rarest Blood Type?
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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