Many know that it’s potentially dangerous for the pregnant mom and her baby to have different blood types. This is tricky, complicated business, however. In many cases, mom and the baby having different types will result in hardly any complications at all. In some, the symptoms will be so mild that there’s no need for treatment. In yet others, it may mean an extended hospital stay, or even an admission in the neonatal intensive care unit.
To understand this variety of reactions, it’s important to learn about blood types and how they’re inherited. After all, it may be difficult for some to wrap their head around how mom and the baby can have different blood types in the first place. It’s important to remember, however, that chromosomes from the mother and the father are present in making the baby, so it’s quite possible that the baby will be the father’s blood type, and not always compatible with the mother’s. It’s also important to understand how the immune system works, as this has an important bearing on the specific set of symptoms that occur when mom and baby have different blood types.
But it’s also important to know that, with modern medicine, it’s perfectly possible to avoid all these dangers completely. Many doctors now encourage blood tests for both the mom and the dad to help calculate the risks. In some countries, these tests are even mandatory.
15 Blood Types Explained
Anyone who has had a blood test will see that the test results will be a combination of one or two letters and either a positive or a negative sign. Each of these actually stand for the presence or absence of distinct proteins, known as antigens, located on the surface of each person’s red blood cells. These surface proteins are among the things that help the body distinguish its “own” cells from that of another, possibly harmful organism. Keep this in mind as it will come to play when we talk about the immune system.
The letters indicate the person’s ABO type, while the positive or negative symbol indicates the RH type. A baby inherits half of the genes that determine blood type from mom, and the other half from dad. Some of these genes are dominant, which means that they will present in the baby no matter what they’re paired with. Others are recessive, which means that if they’re paired with a recessive gene, they won’t appear at all and a baby will need to inherit both recessive genes for her to have that specific blood type. As a general rule, the presence of any antigen is a dominant gene.
14 ABO Type
A person’s ABO type can be either A, B, AB or O. This typing basically determines the presence or absence of two specific antigens: The A antigen and the B antigen. A person who has type A blood has only the A antigen, and a person with type B blood has only the B antigen. A person who as an AB blood type has both antigens, while a person with an O antigen has neither.
The ABO type is a common concern when getting blood for a transfusion. As a general rule, it’s only safe to transfuse blood within people of the same ABO type. In emergency cases, however, cross-transfusion may be possible, as long as a specific set of rules are followed. However, ABO type is rarely a big problem for pregnant moms and their babies, unless the mom has an overactive immune system or the baby is born premature.
13 Rh Type
The Rh type basically indicates the presence of a single antigen on the surface of red blood cells. The Rh antigen is a dominant gene, and is present in 8 out of 10 people. Even if the Rh type is determined by only a single antigen, it often causes far more problems during pregnancy or after childbirth than the ABO type.
The majority of women who are Rh positive should not have any trouble with the baby, even if the little one is Rh negative. Women who are Rh negative, however, may have difficulty with pregnancies with Rh positive babies. If the father is Rh positive, there is a chance that the unborn child will also be Rh positive. In this case, it may be necessary to test the baby’s blood type or, perhaps, begin preventive treatment, especially if the couple want to have more than one child. The mom may carry the first pregnancy with no problems, but the second pregnancy with an Rh positive child may be problematic.
12 Immune System 101
The thing that makes antigens such a concern is the immune system. Now, the immune system functions to protect the body from foreign invaders, often bacteria, viruses, protozoa or fungi that can potentially harm body cells. One mechanism by which the immune system works is through the detection of antigens on these invading cells. If an immune cell meets up with a cell that has an antigen not recognized as friendly, it will produce tiny substances called antibodies.
Antibodies fit into specific antigens like a key to a lock. Once they attach to the antigen, they will either destroy it or mark the cell as a target for tougher immune cells. Production of antibodies, however, can take time. As a result, if an entirely new microorganism affects the body, it may take a while before the body is able to fight back. Once exposed to the antigen, however, the body will be able to produce antibodies against it much faster.
11 You Shall Not Pass
Contrary to popular belief, however, the mom’s blood and the baby’s blood don’t actually mix in the womb. They are, however, only separated by the thin placental barrier. This barrier does not allow maternal and fetal blood cells to cross over to either side. But since the baby is dependent on the mom for some of the building blocks for life, it does allow smaller substances to cross.
These smaller substances include oxygen and nutrients from food. Another set of tiny things that are allowed to cross the placental barrier are, incidentally, antibodies. This is necessary because these antibodies can protect the little one against infection early in life. After all, the newborn’s immune system won’t be fully developed until she’s about four months of age. These antibodies are therefore great for the little one. That is, unless they misidentify the baby’s cells as invaders and target them for destruction.
10 Mixing Blood
So if the placental barrier keeps mom’s and baby’s blood apart, why are antigens a problem? During childbirth, as the placenta detaches itself from the uterus, some of the baby’s placental blood inevitably ends up getting mixed with the mom’s. This is regardless of whether this was a vaginal delivery or a C-section. It also happens in moms who have a miscarriage, stillbirth or abortion. If a diagnostic procedure that involves placental puncture is required, such as with an amniocentesis, mom could also be exposed to the baby’s blood.
This is fine, usually. But if mom has a different blood type, especially if she’s Rh negative, and the baby’s cells have an antigen that is foreign to mom, for instance if the little one is Rh positive, this could spell trouble. Mom’s body just might produce antibodies against the baby’s blood, and since mom is not exposed to antigens until the first childbirth, it’s only when she’s pregnant for the second time that problems could present.
9 Indirect Coombs Test
Moms who are suspected of having antibodies against the baby’s blood type, perhaps due to a previous miscarriage, can be tested through what is called the indirect Coombs test. For this test, a blood sample must be taken from the mother. The blood is then processed so that only a clear fluid, known as serum, remains. This is then exposed to red blood cells of the baby’s suspected blood type.
This usually involves testing an Rh positive sample against the serum of an Rh negative mother. If the blood clumps together following the exposure, the test is positive. This means that mom likely has antibodies against the baby’s blood type. Since these tiny antibodies, unlike the larger antigen-carrying red blood cells, can pass through the placental barrier, they can cause the same sort of reaction in the baby’s blood. And, as you might expect, this can result in a bunch of problems that involve the breakdown of the little one’s red blood cells.
Hemolytic disease of the newborn is the medical term for when the baby’s blood cells get destroyed by antibodies from mom’s blood. When red blood cells break down, one of the by-products is bilirubin. Bilirubin is a yellow pigment that, in large amounts, can irritate body tissue. Bilirubin’s color is the reason why one of the primary signs of hemolytic disease is jaundice.
In some cases, this jaundice is not so serious. If there is too much bilirubin in the blood, the little one might require phototherapy, a treatment in which she is placed under a special light. This light helps with the breakdown and release of bilirubin from the skin so it won’t cause any damage. Premature babies and those with Rh incompatibility are more likely to have serious cases of hemolytic disease. Babies born at term and those with ABO incompatibility are more likely to have milder cases. However, this may depend per situation.
If too many red blood cells are broken down, the little one may get anemia. This is basically when the baby’s levels of red blood cells are low. Red blood cells are vital to normal body function. Blood is liquid and it can be pretty difficult for most gases to travel within it. Red blood cells therefore function by picking up much-needed oxygen when they pass by the air sacs of the lungs, and then delivering them to cells all over the body. Once oxygen is unloaded, red blood cells then pick up carbon dioxide (although some of it will dissolve in the blood in the form of acid) and take this back to the lungs, where the cycle begins anew.
Now, oxygen is essential to cellular life. When cells stay too long without oxygen, they die. In severe cases, when the breakdown of red blood cells is just too rapid, the vital organs may be seriously damaged.
One risk of too much bilirubin buildup is a complication called kernicterus or bilirubin encephalopathy. This is basically a condition in which the brain is damaged by too much bilirubin in the blood. This is because bilirubin can be neurotoxic, or toxic to nerve and brain cells, in high amounts. When jaundice in the newborn is untreated for too long, the damage becomes so great that this complication arises.
A baby who has kernicterus will initially be be lethargic, or sleep a lot and will be limp and probably not feed well. If the condition progresses, she will transition from being overly week to being irritable, with an abnormally arched back and a high-pitched cry, which will sound extremely different from the cry of a normal newborn. In some cases, the baby may also develop a fever, especially if the thermoregulation center of the brain is affected. In the later stages, the baby will grow weak again and may develop seizures.
5 Long-Term Effects
When detected and treated early, hemolytic disease will resolve quickly and no serious complications will arise. Unless, of course, the baby has a particularly serious case, in which aggressive treatment will be necessary. Babies who have developed severe anemia due to hemolytic disease may experience problems with the spleen and liver. They may also experience cardiovascular or neurological problems.
Babies with kernicterus might have problems with movement. Some might experience muscle twitches or spasms, depending which part of the brain was affected. They may also develop problems with hearing. Other babies may not be able to move their eyes properly. In particular, they may have trouble looking up. In addition, they may also experience learning or developmental problems later on. If the little one has experienced any of these complications, therefore, it is important to monitor her development through the years so that any problems can be caught and addressed early.
Blood type incompatibility might mean that mom is at risk for miscarriage in the future. This usually starts when the little one begins to develop a circulatory system and produces red blood cells. Once these “foreign” red blood cells are detected by maternal antibodies, they may attack them. This can result in a miscarriage or, if the pregnancy carries on far enough, stillbirth. Because of these, moms who have frequent miscarriages may want to get a blood test, especially if she has had poor access to medical care. A mom who is blood type O or is Rh negative is at risk of having frequent miscarriages, especially if her partner has an antigen-positive blood type.
In milder cases, the baby might be carried to term and be born live. However, there is a risk of getting hemolytic disease of the newborn, in the period after birth.
One of the best ways to prevent hemolytic disease of the newborn begins with mom and dad getting a blood test to determine their blood types. It may also be useful to know the grandparents’ blood types as well. Once the doctor knows their types, it’s fairly easy to calculate the baby’s chances of having certain blood types. As we’ve suggested earlier, a mom with type O or Rh negative blood will have any of the antigens and so will be more prone to producing antibodies against the little one.
But moms in this situation need not worry. If the possible incompatibility is detected early, the doctor can give the mom intravenous immune globulin or IVIG. This suppresses the mom’s production of antibodies against the future baby’s red blood cells. With this treatment, it is entirely possible to carry complication-free pregnancies even with blood incompatibility. Of course, this treatment is best done before mom gives birth to her first child.
2 Close Monitoring
If, however, it’s too late for the mom-to-be to receive immunoglobulin treatment and it’s highly likely that the mom’s immune system will target fetal red blood cells, it’s important to monitor the fetus for possible complications. In some of the milder cases, symptoms will not present during the pregnancy. This is because the placenta is still able to take bilirubin and return it to maternal circulation, where mom’s liver metabolizes it into something less harmful. However, if the destruction is so fast that it results in anemia, the fetus may experience enlargement of the liver and spleen. In some cases, this will result in the swelling of the little one’s tissues, a dangerous condition called hydrops fetalis.
But just because the little one is clear of symptoms during pregnancy doesn’t mean they’re not going to pop up during childbirth. In the newborn, the still immature liver may not be able to process the bilirubin load as well as the mom can. In this case, hemolytic disease may develop after childbirth.
1 Exchange Transfusion
In the most severe cases of hemolytic disease, the baby will require a more aggressive treatment called an exchange transfusion. This is a process in which the baby’s own blood will be removed from the body while, at the same time, transfusing a donor’s blood that is negative for antigens. This is more commonly done with babies and moms who are Rh incompatible, and hardly ever necessary with ABO compatibility. This is done when phototherapy is unsuccessful and there is a very high risk of developing potentially life-threatening complications such as kernicterus and severe anemia.
As with any procedure of this scale, there are risks involved. The little one may experience blood clotting or imbalances in blood composition. However, in severe cases, it may be necessary to give the baby a shot at survival. Fortunately, due to IVIG preventive therapy and more accessible prenatal checkups, this procedure is now very rarely done.