Rh incompatibility occurs in pregnancies in which mothers are Rh-negative (Rh -) and fathers are Rh-positive (Rh+). Rh antigen can commonly be found in erythrocytes (red blood cells) of monkeys and much rarely in the ones of humans. The presence or absence of Rh antigens in humans should not be considered a disease. The problem occurs when an Rh-negative mother (Rh-) has a child with an Rh-positive partner (Rh+), and the baby’s blood type is Rh-positive (Rh+).
In couples with an Rh mismatch, the mother usually does not have any specific symptoms. However, in a situation where the fetus develops anemia and edema (dropsy) due to blood incompatibility, the mother may sometimes have a condition called mirror syndrome, when the mother may also have the same symptoms. Since in the case of Rh incompatibility, the fetus (the baby in the womb) suffers first, and mirror syndrome is pretty rare, waiting for the manifestation of this problem in the mother should not be a diagnostic method. The main symptoms of Rh incompatibility occur in the fetus and can only be diagnosed by ultrasound.
Infants whose mothers have a negative Rh factor and fathers have a positive one are at risk of Rh incompatibility. In the case of Rh incompatibility (in the unions of Rh-positive and Rh-negative partners), when fetal blood enters the mother’s body through the placenta (which can be caused by amniocentesis, taking samples of the villous chorion, childbirth, or trauma), the mother develops immunity and antibodies against Rh antigens, with which she meets for the first time. The mother’s first exposure to the Rh antigen and subsequent development of immunity is usually not a problem in the first pregnancy. Because the first antibodies produced are in the structure of immunoglobulin M (Ig M), which is too large to pass through the placenta to the baby. However, in the long run, the mother’s immune system changes and starts to produce a different antibody type called IgG, which can already pass through the placenta. If the child is Rh-positive, the antibodies that pass from the placenta to the fetus combine with the antigens of the red blood cells of the baby and can provoke the destruction of its red blood cells (hemolysis) and, ultimately, under the influence of various mechanisms, cause fetal anemia. Anemia, which occurs in a baby, can cause oxygen starvation of tissues, heart failure, lack of protein due to the tendency of the liver to produce a large number of red blood cells instead of protein, as well as the accumulation of fluid in the body cavities (dropsy), (Figure 1). In cases where medical intervention does not occur, the fetus usually does not survive.
To diagnose Rh incompatibility, you need to know the blood groups of the mother and father. By periodically taking an indirect Coombs sample during pregnancy monitoring, it is possible to understand whether the mother is sensitized due to Rh incompatibility or not. If the mother’s indirect Coombs test is positive, it means that the mother’s body produces antibodies, and the child is at risk. Heart failure and lack of protein due to anemia in the last stage cause the fetus to accumulate fluid (edema) in the cavities of the baby’s body (chest, abdomen, and pericardium). The formation of fetal dropsy is the stage at which the problem progresses, and the effectiveness of the intervention decreases. Before the development of edema, the presence of anemia in a child can be diagnosed with an accuracy of up to 90 percent by measuring the blood flow rate in the vessels of the fetal brain (in the middle cerebral artery, MCA) using Color Doppler ultrasound. These amenities and opportunities have become available to us thanks to the latest technology. Infants with anemia are treated in the womb, which helps them to be successfully cured. The fetal hemoglobin level can be measured in the laboratory by taking blood from the baby’s umbilical cord (cordocentesis).
In the case of anemia of the fetus, for the reasons mentioned above, edema (accumulation of fluid in the abdomen, chest, around the heart, and under the skin) may be detected. However, the presence of this indicates that the situation has already worsened. Before the development of edema, the presence of anemia in a child can be diagnosed with an accuracy of up to 90 percent by measuring the blood flow rate in the vessels of the fetal brain (in the middle cerebral artery, MCA) using Color Doppler ultrasound. Apart from that, the fetal hemoglobin level can be measured in the laboratory by taking blood from the baby’s umbilical cord (cordocentesis).
Since Rh incompatibility mainly causes fetus anemia and, ultimately, its death, the treatment consists of providing blood to the baby. In today’s conditions, blood transfusion to the fetus in the womb is done by using ultrasound. Red blood cells, obtained from red blood cells that do not contain the Rh factor antigen, and have a higher concentration compared to the average person, are transmitted to the baby through the umbilical cord. This is how blood transfusions are performed in the womb. This procedure, depending on the week of pregnancy, must be performed more than once and usually continues until the baby is able to live and born healthy. Video 1 shows the procedure of blood transfusion in the womb to one of the babies in our clinic.
Video 1: A case of Rh incompatibility and fetal edema, which we diagnosed and cured by blood transfusion, accompanied by ultrasound, through the umbilical cord to the fetus in the womb.
In addition to Rh incompatibility, there may be incompatibilities of certain red blood cell antigens (Kell, Duffy, Kidd, E, C, etc.), as well as sometimes bone marrow suppression infections that may require blood transfusions to the baby in the womb.