Rh blood group system is one of the most prominent classifications of the human blood group. During pregnancy, blood group incompatibility can occur if a mother who is RhD negative is pregnant with a fetus who is RhD positive.
Blood group difference between the baby and the mother can cause Rhesus disease. Rhesus disease does not affect the mother but the baby born is severely anaemic and jaundiced.
To understand how it happens, we need to know what happens when the baby and the mother are of opposite Rh groups.
Sensitisation is a process that occurs when a woman with RhD negative blood is exposed to RhD positive blood. Just as individuals allergic to particular foods have an allergic response, a mother's body reacts to the foreign antigens of her baby's blood by producing antibodies that recognize the blood cells as harmful and destroy them.
If she conceives a baby who is RhD positive, the antibodies can cross the mother's placenta and attack the baby's cell system. This condition is called Rhesus disease.
This is when Anti-D comes in the picture. Rhesus disease can be prevented by providing medications of anti-D Immunoglobulin. It belongs to a group of drugs called immunoglobulins which work towards making the immune system perform better. Without anti-D, the chances of rhesus disease in the baby are high and can lead to stillbirth. In other cases, it could lead to learning difficulties, deafness, and blindness. However, treatment is usually effective and these problems can be avoided. The use of anti-D has greatly reduced the disease incidence by decreasing the chances of a mother forming antibodies from about 1.5% to 0.2%.
It is a part of prenatal care to offer all RhD negative mothers Anti-D immunoglobulin injections during pregnancy. The two doses administered are generally at week 28 and week 34. This is because it is likely that small amounts of blood from your baby will pass into your blood during this period of time. The injections may continue after delivery if the baby is born RhD positive. You may need to have the injection earlier if you had:
• any vaginal bleeding during your pregnancy;
• a miscarriage previously;
• an abortion before.
Anti-D immunoglobulin is made up of blood plasma and the injection is generally given into a muscle in your arm or leg.
After giving birth, a sample of your baby's blood will be extracted from the umbilical cord. If you both are of the opposite groups, and you haven't already been treated, you will be offered an injection of anti-D immunoglobulin within 72 hours of giving birth. The injection will destroy any RhD positive blood cells that may have crossed over into your bloodstream during the delivery. This will significantly reduce the risk of your next baby having rhesus disease.
Also read: Jaundice During Pregnancy: Impact On Babies