Upon your initial visit to the care provider's office, you will often be asked a list of medical questions, so your physician can obtain a detailed history of your health. Knowing the blood types of both mother and father of the baby is very important in ensuring the health of the fetus. This article will explain the ABO and Rh blood types and the role genetics plays as well as potential risks to the unborn baby/newborn as a result of the difference between mother's and baby's blood types.
Everyone has a specific blood type. The most common classification system is the ABO system. Karl Landsteiner discovered and formulated this system in 1900-1901 while he was investigating why blood transfusions could cause death in one patient while saving the life of another patient. This work earned him the Nobel Prize nearly 30 years later.
Basically, there are four blood types in the ABO system: A, B, AB, and O. Your blood type is actually established before you are born. At conception, one gene from your mother combines with one gene from your father, determining your individual blood type. As Landsteiner discovered, blood can be grouped (or typed) based on the surface of the red blood cells and certain antibodies in the blood plasma.
There are three versions of the blood type gene: A, B, and O. Since we each have two copies of these genes, one from each parent, there are six possible combinations: AA, AB, OO, BB, AO, and BO. These combinations, or genotypes, describe the genes we obtain from our parents.
With this in mind, let's look at what makes one individual's blood type compatible with another individual's. The table below shows the ABO blood types and corresponding presence (yes) or absence (no) of antigens and antibodies. For example, type A people will have the A antigen on the surface of their red cells. Therefore, anti-A antibodies will not be produced because they would cause destruction of their own blood. However, if B type blood is injected into their body, anti-B antibodies in their blood system will recognize it as an alien, attacking and destroying the foreign, introduced red cells.
In addition, type O people do not have any ABO antigens. Their blood normally will not be rejected when given to others with a different ABO type. This makes type O people "universal donors" for transfusions.
In pregnancy, maternal-fetal incompatibility of blood types can occur. This is usually very rare — less than 0.1% of births. ABO incompatibility occurs most commonly when the mother is type O and her fetus is A, B, or AB. Symptoms in newborns can include jaundice (yellowish coloring to the skin), mild anemia, or elevated bilirubin levels. A baby showing these symptoms will have a blood test to check these levels. Treatment for high bilirubin levels includes phototherapy (bili lights), which helps break down excess bilirubin. This treatment is usually successful, so there is no need for a blood transfusion.
Another aspect of your blood type that is extremely important to know in pregnancy is the Rh classification. The Rh system, named after the rhesus monkey, was developed while researching an antiserum for typing blood samples. If the antiserum agglutinates (clots) your red cells, you are Rh+. If it doesn't, you are Rh-.
Your Rh type is important in pregnancy because mother-fetus blood incompatibility can occur when the mother is Rh- and the unborn baby is Rh+. This is a serious and potentially life-threatening situation for the growing fetus. An Rh- mother will produce antibodies to Rh+ blood if it enters her system. When birthing a baby, placental rupture normally occurs. This causes some fetal blood to enter the mother's system, thus stimulating the development of antibodies if the baby is Rh+ and the mother is Rh-. This poses a serious risk to any future Rh+ babies a woman may have. When the next pregnancy occurs, the mother's anti Rh+ antibodies transfer across the placenta into the fetus. There they will react with the fetal blood, attacking the red blood cells and causing them to burst. As a result, the newborn baby may be born with life-threatening anemia, causing a lack of oxygen in the blood. Baby may also be jaundiced, fevered, and have an enlarged liver and spleen. This is called erythroblastosis fetalis. The good news is that this serious condition is preventable. As a part of their prenatal care, women at risk (Rh- women with Rh+ mates) can receive a serum called Rho-GAM. The Rho-GAM injection contains anti-Rh+ antibodies in a small dose and is given to the expectant mother around the 28th week of pregnancy and again within 72 hours after the delivery of an Rh+ baby. This important treatment can be 99% effective in preventing erythroblastosis fetalis by acting as a passive form of immunization. The Rho-GAM prevents the mother from forming her own long-lasting antibodies. The Rho-GAM antibodies are temporary, leaving the bloodstream after a short period. Rho-GAM is also given to Rh- women after a miscarriage, an ectopic (tubal) pregnancy, or an abortion.
By giving that blood sample at your prenatal visit for laboratory testing, many important facts about your blood are discovered which can have a direct impact on your unborn baby. When an Rh- woman takes a Rho-GAM injection, it is an important step in protecting the health of her unborn child and provides protection for her future children.