What Happens When You Get a RhoGAM Shot

During your pregnancy, you'll need to know if you have the rhesus protein. If not, you might get a RhoGAM shot. Here's how it works.

pregnant woman getting vaccine in doctors office
Photo: Ariel Skelley/Getty Images

Early in your pregnancy, you'll take a blood test to determine whether you are Rh-positive or Rh-negative. Rh, or rhesus, is a protein that rides along on the surface of the red blood cells of about 85 percent of people. If the protein is found on your red blood cells, you are Rh-positive—and if it's not there, you're Rh-negative.

The presence or absence of the rhesus protein really only matters when you're pregnant with your second or subsequent child. Keep reading to learn the reason, and figure out what to expect if you need a RhoGAM shot.

Why Do Pregnant Women Test for the Rhesus Protein?

If you're Rh-negative and your baby's blood is Rh-positive, and it makes contact with yours during your first pregnancy, your body begins to produce antibodies because it doesn't recognize the Rh protein present in your baby's blood. Think of antibodies as little warrior cells who go off to do battle against invading forces. Any time you are exposed to an antigen, your body produces antibodies specific to that antigen, so if it attacks again, your immune system is ready to fight it off.

This is why your Rh factor isn't an issue during first pregnancies. It isn't until second and subsequent pregnancies when antibodies are already built up, that Rh incompatibility can cause problems. Indeed, these antibodies can cross the placenta and attack your baby's red blood cells. This can cause your baby to develop anemia, and in severe cases, result in miscarriage.

Since you and your baby don't share circulation, there are only a few points during pregnancy that fetal blood can come into contact with maternal blood. Tami Prince, M.D., of Women's Health and Wellness Center of Georgia, says cross-contamination can occur "during early pregnancy bleeding, procedures such as an amniocentesis or CVS (chorionic villus sampling), direct abdominal trauma, ectopic pregnancy, miscarriage, or blood transfusion with mismatched blood typing."

To prevent complications, "it is critical that an Rh-negative woman be treated with Rh immunoglobulin if bleeding occurs in order to prevent antibody formation," Dr. Prince says. Luckily, there's an injection women can receive during pregnancy to counteract Rh incompatibility: the RhoGAM injection.

What is the RhoGAM Shot?

RhoGAM is an injection made up of antibodies called immunoglobulin that help protect a fetus from its mother's antibodies. According to the product website, "RhoGAM prevents the Rh-negative mother from making antibodies during her pregnancy. As long as the Rh-negative mother receives RhoGAM appropriately during every pregnancy, her babies are at very low risk of developing [anemia]."

Sheila Chhutani, M.D., of Gyn/OB Associates in Dallas, Texas, tells Parents.com, "RhoGAM is immunoglobulin, or manufactured antibodies, that will attach to the rhesus protein in the mother's blood, not allowing her body to process or 'see' that protein to start manufacturing her own antibodies. The RhoGam does not cross the placenta and will not harm the baby."

When Do Women Get the RhoGAM Injection?

According to Dr. Chhutani, "The injection is typically given at 28 weeks gestation because it will last for about 12 weeks. At delivery, if the newborn is Rh-positive, the mother will receive another dose of RhoGAM." This last injection is given just in case there was any cross-contamination of blood from baby to mother during delivery. One last dose of immunoglobulin will prevent the mother's body from producing antibodies that may place future pregnancies at risk."

RhoGAM Side Effects

RhoGAM side effects are usually mild and don't harm the baby or affect breastfeeding. They might include swelling and/or redness at the injection site, itching at the injection site, and mild fever. Less common side-effects can include allergic reaction, headache, joint or muscle pain, and fatigue. If any of these are experienced, you should talk to your doctor.

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