Rh Factor and Pregnancy
At your early OB appointments during pregnancy, you may have heard mumblings about your Rh factor or Rh status. Rh (short for Rhesus) is a protein that is usually present in red blood cells. Most women have it and are considered Rh positive. However, if you are Rh negative, you’ll need to take some extra steps during your pregnancy for the safety of your baby and future children.
Early in your pregnancy you will likely take a blood test to verify your blood type and determine if you are Rh positive or Rh negative. There are four human blood types – A, B, AB and O – which are determined by antigens or proteins found in your blood. Rh factor is yet another type of antigen or protein. The majority of women are Rh positive. Asian and African-American women as groups are 90% Rh positive or higher, while around 85% of Caucasian women are Rh positive.
Complications due to Rh factor only arise during pregnancy and childbirth if a mother and baby have opposite Rh factors. It is unlikely that you will know your baby’s Rh factor prior to birth so it is safest to assume that your baby is Rh positive. Therefore, if you test Rh negative, you will need to take precautions during pregnancy.
During a first pregnancy, incompatible Rh factors may not make a difference during pregnancy; however it can cause problems in future pregnancies. In the unlikely event that your first baby’s Rh positive blood seeps into your Rh negative blood stream during pregnancy, your immune system may build up antibodies against it. The next time you become pregnant with a Rh positive baby, your body could attack your baby’s blood and cause major problems.
The most likely time for your blood to mix with your babies is during childbirth. Because this is such a short time, your body may not even have a chance to develop antibodies, but it is important to know your status and take precautions in advance anyways. If you are Rh negative, you will be given a shot of Rh immune globulin at some point during your second trimester. This will prevent your body from creating antibodies against your baby’s Rh positive blood and combat any contamination that your baby’s blood may cause in your system.
If your first or subsequent babies are exposed to the antibodies that your immune system produces against their blood, it could lead to Rh disease or hemolytic disease. This disease causes your baby to have anemia and your baby may be jaundice or have other birth defects. In some cases if it happens during pregnancy, it can lead to miscarriage or stillbirth.
You will probably know your Rh factor from your first pregnancy. If you are unsure, you can have a simple blood test to re-check your status. Also, blood work can show if your body ever developed antibodies to a previous baby’s incompatible blood. Additionally, you can determine the likelihood of your baby’s Rh factor by knowing the father’s Rh factor. If you and the father are negative, your baby will surely be Rh negative as well and then no shot or risk of complications are present.
Fortunately, with proper and consistent prenatal care, not knowing and acting on incompatible Rh factors is highly unlikely. The most important step is being aware and take proper precautions to keep you and your baby safe.