The Rhesus, or Rh, blood group is part of 35 known blood group systems in humans and is the second most important blood group after the ABO system.1 The latter blood group system is the one that determines if we have A, B, AB, or O type blood and this depends on which of these proteins are present on the surfaces of our red blood cells.
The Rh blood group system involves 50 different blood group proteins and the five most important ones are D, C, c, E, and e. When Rhesus tests are performed on an individual, it determines whether the D antigen is present on the surface of the red blood cells or not and this is indicated by stating that the person is either Rh positive or negative. The presence or absence of the D antigen on the surface of the red blood cells depends on the individual’s parents since the protein is inherited and around 85 percent of humans are Rh positive.
History of Rhesus
The Rhesus blood type was discovered in 1937 and named after the Rhesus monkey. The reason for this was because serum containing the antigens of the Rhesus blood group was produced by rabbits that were immunized with the blood of a Rhesus macaque.2
In certain situations, a Rh incompatibility between individuals may result in a medical condition known as hemolytic disease of the newborn or Rhesus disease where the red blood cells in the bloodstream of the fetus are damaged due to antibodies attacking the surfaces of the cells.3 During a pregnancy, the expectant mother is tested at her ante-natal examination to determine what her Rh status is.
The mother is Rh negative
In this case, the father of the child is also tested and one of two scenarios occurs.
- If the father is Rh-negative, then the fetus will also be D antigen negative and there won’t be any incompatibility issues.
- If the father is Rh positive, then there is a chance that the fetus will also be Rh positive. What this means is that when the mother and fetus’ blood come into contact with each other, the maternal blood will recognise the fetus blood as foreign (because there’s no D antigen on the surface of the red blood cells) and the maternal immune system will start to produce antibodies known as IgG anti-D antibodies which attack the D antigens and this results in damage to the red blood cells of the fetus. The baby from the woman’s first pregnancy won’t really be affected because maternal and fetal blood only comes into contact with each other during childbirth, whether it’s a normal vaginal delivery or via Caesarean section. The time of exposure is therefore limited and no damage to the baby’s red blood cells occurs. Rhesus disease will be an issue in the proceeding pregnancies though because the mother has the anti-D antibodies circulating in her bloodstream and this will come into contact with the next fetus and cause damage to its red blood cells.
The mother is Rh positive
- Since most people are Rh positive the father won’t routinely be tested. If he is and the result is Rh positive then the fetus will also be Rhesus positive.
- If the father is Rh-negative, there is a chance that the fetus will also be Rh negative. This scenario isn’t as problematic as the aforementioned issue because when there is contact between the mother and baby’s blood, the child’s immune system will produce the IgG anti-D antibodies. However, this won’t matter because the mother and child’s blood doesn’t come into contact again after childbirth. Where this scenario may be problematic is if the child is female, as she has the potential to become pregnant later on in life, and she has circulating anti-D antibodies that may affect her fetus if it’s Rh positive.
Nowadays though, if there’s a Rh incompatibility issue where the mother is Rh negative, an IgG anti-D vaccine is administered to the mother during and after the pregnancy to prevent her immune system from producing the antibodies. Make sure you follow the right test. At Xpertdox you can find best doctors or hospitals for treating any rare disease.
1. Dean L. Blood Groups and Red Cell Antigens [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2005. Chapter 7, The Rh blood group. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2269/
3. Dean L. Blood Groups and Red Cell Antigens [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2005. Chapter 4, Hemolytic disease of the newborn. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2266/