Early in your pregnancy, one of the battery of tests you'll take is 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, if it's not there, you're negative. Pretty much the only time in your life this presence or absence of the Rhesus protein will matter is when you're pregnant with your second or subsequent child.
Let's break down how our bodies work: Your body's immune system "reads" the surfaces of your cells for foreign or unfamiliar proteins, and if a cell is determined to have unfamiliar proteins, your body reacts by producing antibodies for that particular protein. Think of antibodies as little warrior cells who go off to do battle against invading forces. Anytime 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.
If you are Rh-negative and your baby's blood is Rh-positive and 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.
Remember: 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."
"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. If not, and your baby during a subsequent pregnancy is Rh positive, there will be an immune response and your 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.
Luckily, there's an injection women can receive during pregnancy to counteract Rh incompatibility: the RhoGam injection.
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."
Dr. Chhutani adds, "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."
Side-effects are usually mild and don't affect the baby or breastfeeding after delivery. Common RhoGam side-effects 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.