| While many people are aware about genotype and the need to do genotype tests before marriage, very few know what Rhesus factor is, or how it can affect pregnancy and lead to rhesus disease or Rhesus Isoimmunization. |
Many a couple have experienced miscarriages, still births and health problems in their babies without knowing it may be linked to rhesus incompatibility between mother and child.
Talatu (not her real name) said she couldn’t understand why she kept experiencing miscarriages after the birth of her son. She said it was when her husband was transferred to another town, that tests at a hospital revealed that she is rhesus negative and her husband positive. She said she was given a particular injection during the first trimester of her last pregnancy and recently gave birth to another son.
What is Rhesus Factor?
The Rhesus factor (Rh factor) is a protein that can be found on the surface of red blood cells, says the American College of Obstetricians and Gynaecologists (ACOG). It says if your blood cells have this protein, you are Rhesus positive and if your blood cells do not have it, you are Rhesus negative.
Explaining the concept, Dr. Alechenu M. Obaje of the Department of Obstetrics and Gynaecology, Federal Medical Centre, Azare, Bauchi State, said the blood is made up of cells which possess proteins called antigens on their surfaces. He said the presence of these antigens on the cells accounts for the blood group system, adding that there are several blood group systems recognized but the ABO and Rhesus system dominate (representing over 98%) based on the antigens expressed on the blood cells.
“The ABO system groups individuals into blood group types A, B, AB and O. Each of these blood types has Rhesus antigens grouped in three pairs of Cc, Dd, Ee; the major one being the D antigen. When present, the person is said to be Rhesus positive and where absent, it is Rhesus negative,” he explained.
Rhesus disease or isoimmunization
Dr Obaje said since half of the human genetic component comes from each parent to the unborn baby, Rhesus incompatibility can occur in a sensitized Rhesus negative mother who is pregnant with a Rhesus positive fetus, where the father is also Rhesus positive. This incompatibility will result in Rhesus disease or Rhesus Isoimmunization, he said.
The difference between the ABO (blood group) incompatibility and Rhesus Isoimmunization is that the former is a condition associated with blood transfusion reaction where a patient is transfused with blood of a different group other than his blood group while Rhesus Isoimmunization is a chain of immune system reaction between a sensitized Rhesus negative mother and a Rhesus positive fetus.
How Rhesus disease or Rhesus Isoimmunization occurs
The consultant gynaecologist and obstetrician said rhesus disease or isoimmunisation rarely occurs during the rhesus negative woman’s first pregnancy because her body does not have a lot of chance to develop so much antibodies, adding though that in the course of the first pregnancy, exposure may occur if there is blood mixing of the rhesus positive fetus blood cells with the Rhesus negative mother cells.
Dr Obaje said: “When this mixing occurs (feto-maternal haemorrhage) there will be development of antibodies in the mother against the Rhesus positive cells of the baby. Since it does so slowly, the pregnancy would have ended or completed before these antibodies are well established.
“But in subsequent pregnancies, these antibodies can cross from the mother into the fetus through the placenta and bind to the blood cells of the fetus causing destruction of red cells of varying degrees and leading to anaemia in the baby. In severe cases, the baby develops severe swelling (hydrops fetalis), disease where the mother’s white blood cells attack her baby’s red blood cells (Erythroblastosis fetalis), and major organ damage like brain, kidney, heart failure and even death (still born) may occur.”
He said Rhesus Isoimmunization can also occur when a Rhesus negative woman is transfused with blood of a Rhesus positive donor, adding that this exposure leads to sensitization through the production of antibodies in the mother which can affect her baby when she gets pregnant.
The medical expert said the process or procedures that can lead to sensitization in a Rhesus negative woman via blood mixing between the fetus and mother are miscarriages, ectopic pregnancies, invasive procedures like chorionic villus sampling, amniotic fluid test, process of turning a breech baby to right direction called external cephalic version, manual removal of placenta, manual vacuum aspiration, caesarian section and delivery, among others.
These antibodies remain in the maternal blood circulation for life and can harm a Rhesus positive fetus when the woman is pregnant, he said.
Dr Obaje said Rhesus Isoimmunization has negative impact on the society as issues of marital disharmony have ensued, especially where couples and their relations misconceive the issue of recurrent pregnancy loss or still births to other concepts.
“Aside this, babies that survive complications arising from this disease have major organ affectation that predisposes them to various forms of life long disabilities,” he warned.
Screening and interventions to prevent Rhesus disease
Screening for Rhesus disease begins with everyone particularly women being aware of their Rhesus status and also that of their partners.
If both couples are Rhesus negative, the risk of the disease is ruled out, said Dr Obaje. However, where the male spouse is Rhesus positive and the female is Rhesus negative, the risk for Rhesus Isoimmunization exists. Precautions must therefore be taken to prevent this catastrophe.
According to Dr Obaje, when a woman with the risk mentioned above becomes pregnant, she requires early ante-natal clinic care. “She will be evaluated for the presence of antibodies that will reveal whether blood mixing has occurred. This is done periodically using the indirect coomb’s test. As long as the result is negative, she remains unsensitized and hence the baby is unlikely to be affected.”
He explained that the fetus is monitored closely by fetal surveillance and at delivery, she is given anti-D immunoglobulin injection (Rhogam) preferably within 72 hours of child delivery. “This will prevent her from being sensitized as the injection is capable of mopping up any fetal Rhesus positive cell infiltrations from the baby.”
In the event that the Rhesus negative pregnant mother is found to be sensitized evidenced by a positive indirect coomb’s test, the expert advised that measures should be taken to prevent or minimize fetal affectation. The level of these anti bodies can be monitored periodically and if increasing, then delivery of the baby is considered, he said.
The expert said treatment for the severely anaemic fetus is done through before birth transfusion. While anaemia is a major problem for the baby before birth, jaundice is the problem after birth. In this case phototherapy and exchange blood transfusion are measures that are employed.
In some Rhesus negative mothers that are already sensitized and with high level of antibodies in their circulation, plasmapheresis which is like a dialysis procedure is done to reduce the amount of antibodies and hence improve pregnancy outcome.
The concept of surrogacy, egg donation or child adoption might be sought in a few extreme situations, Dr Obaje advised.
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