The adult human body is home to trillions of red blood cells (also known as erythrocytes or RBCs). These blood cells carry oxygen, iron, and many other nutrients to the appropriate places in the body. When a woman is pregnant, it’s possible that her baby’s blood type will be incompatible with her own. This can cause a condition known as erythroblastosis fetalis, where the mother’s white blood cells attack the baby’s red blood cells as they would any foreign invaders.
Also known as hemolytic disease of the newborn, this condition is highly preventable. Catching it early can ensure a successful pregnancy for mother and child. If left untreated, this condition can be life-threatening for the baby.
There are two main causes of erythroblastosis fetalis: Rh incompatibility and ABO incompatibility. Both are associated with blood type. There are four blood types: A, B, AB, and O. And blood can be either Rh positive or Rh negative. If a person is type A and is Rh positive, they have A antigens and the Rh factor antigens on the red blood cell membrane surface. If a person has AB negative blood, they have both A and B antigens without the Rh factor antigen.
Rh incompatibility occurs when an Rh-negative mother is impregnated by an Rh-positive father. The result can be an Rh-positive baby. In such a case, the baby’s Rh antigens will be perceived as foreign invaders, the way viruses or bacteria are perceived. The mother’s blood cells attack the baby’s as a protective mechanism that can end up harming the child.
If the mother is pregnant with her first baby, Rh incompatibility is not as much of a concern. However, when the Rh-positive child is born, the mother’s body creates antibodies against the Rh factor, which will attack the blood cells if she becomes pregnant with another Rh-positive baby.
Another type of hemolytic disease of newborns is ABO blood type incompatibility. This occurs when the mother’s blood type of A, B, or O is not compatible with the baby’s. This condition is considered less harmful or threatening to the baby than Rh incompatibility. However, babies can carry rare antigens that can put them at risk for erythroblastosis fetalis. These antigens include:
To diagnose erythroblastosis fetalis, a doctor will order a routine blood test during an expectant mother’s first visit. This will test for the mother’s blood type, and it will determine whether she has anti-Rh antibodies in her blood from a previous pregnancy. If she has Rh-negative blood and Rh antibodies, the father’s blood will be tested. If the father's blood type is Rh negative, no further testing is needed. But if the father's blood type is Rh positive, or if he has the anti-Rh antibody, the mother's blood will be tested again between 18 to 20 weeks of pregnancy and again at 26 to 27 weeks.
The fetus’s blood type is rarely tested. It’s difficult to test a fetus’s blood type and doing so can increase the risk for complications. A mother’s blood is continually tested for antibodies throughout her pregnancy — approximately every two to four weeks. If the antibody levels start to rise, a doctor may recommend a test to detect fetal cerebral artery blood flow, which is not invasive to the baby. Erythroblastosis fetalis is suspected if the baby’s blood flow is affected.
If a baby is jaundiced (appears yellow in skin color due to a build-up of bilirubin) after birth, but Rh incompatibility is not suspected, the baby may be experiencing problems due to ABO incompatibility. This occurs most frequently when a mother with an O blood type gives birth to a baby who has an A, B, or AB blood type. Because O blood types have both A and B antibodies, the mother’s blood can attack the baby’s. However, these symptoms are generally thought to be much milder than an Rh incompatibility.
ABO incompatibility can be detected via a blood test known as a Coombs test, which is performed after the baby is born. This can indicate why a baby may appear jaundiced or anemic.
Babies who experience erythroblastosis fetalis symptoms may appear swollen, pale, and/or jaundiced after birth. A doctor may find that the baby has a larger-than-normal liver or spleen. Blood tests can also reveal that the baby has anemia or a low red blood cell count.
Babies can also experience a condition known as hydrops, where fluid starts to accumulate in spaces where fluid is normally not present. This includes spaces in the abdomen, heart, and lungs. This symptom can be harmful because the extra fluid places pressure on the heart and affects its ability to pump.
A preventive treatment known as RhoGAM, or Rh immunoglobulin, can reduce the mother’s reaction to the baby’s Rh-positive blood cells. This is administered as a shot at around the 28th week of pregnancy. The shot is administered again at least 72 hours after birth if the baby is Rh positive. This prevents adverse reactions for the mother if any of the baby’s placenta remains in the womb.
If a baby experiences erythroblastosis fetalis in the womb, they may be given intrauterine blood transfusions to reduce anemia. When the baby’s lungs and heart mature enough for delivery, a doctor may recommend delivering the baby early.
After a baby is born, further blood transfusions may be necessary. Giving the baby fluids intravenously can improve low blood pressure. The baby may also need temporary breathing support from a ventilator or mechanical breathing machine.
Babies born with erythroblastosis fetalis should be monitored for at least three to four months for signs of anemia. They may require additional blood transfusions. However, if proper prenatal care and postpartum care are delivered, the baby should not experience long-term complications.