What You Should Know about Your Blood Group

By Dr. Okechukwu Amako, MBBS (Ibadan)
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You must have been asked about your blood group either by a doctor in a hospital or before donating blood for other people. But do you know why understanding the concept of blood group is important for everyone?

Blood grouping is a way of classifying the blood type of people based on the nature of a specific chemical substance (called an antigen) present on the surfaces of their red blood cells. Hence, the different blood groups which are represented as A, B, AB and O. In addition, one’s blood group is either positive or negative, for instance, blood group A positive or A negative.

If your blood group has the positive sign, it means your red blood cells contain another unique chemical substance, known as a rhesus (represented as Rh) factor, on their surfaces; if it has the negative sign it means this unique chemical substance is absent: about 85% of people in the world have this rhesus factor (they are rhesus, Rh, positive) while the remaining 15% don't have it (they are rhesus, Rh, negative).

Knowing your blood group is important because:

1. It helps you know who you are compatible with in terms of donating or receiving blood.

If your blood group is A you can receive blood from someone whose blood group is either A, AB or O (especially if it is O negative), but can only donate to a blood group A or AB person. If your blood group is B, you can receive blood from a B, AB or O blood group donor, and you can donate to a B or AB blood group recipient.

If your blood group is AB, you are a universal recipient, meaning you can receive blood from any blood group: A, B, AB or O, but can only donate to an AB blood group recipient.

People whose blood group is O can only receive blood from O blood group donors. But these people are important blood donors, especially the O negative ones, because they can donate their blood (they are called universal donors) to any blood group--A, B, AB and O.

2. Knowing your blood group as a woman can help prevent your pregnancy from ending in a stillbirth.

The immune system of people with a rhesus negative blood group produces antibodies when a rhesus positive blood enters their blood circulation. This can happen in two ways: if the person is transfused with a rhesus positive blood, and during pregnancy of a baby with a rhesus positive blood group for a woman.

A pregnant woman with a rhesus negative blood group carrying a baby whose blood group is rhesus positive will produce antibodies against the baby's red blood cells if their blood mixes. How? Some of the baby's blood will likely enter the mother's bloodstream during delivery if there is a miscarriage, voluntary abortion or the woman bleeds in pregnancy. When this happens, the woman's immune system produces antibodies against the red blood cells that entered her body from the baby. This first baby will likely not have any issues. However, any pregnancies after this will have serious issues if the woman is not monitored very closely by experienced obstetricians and her newborn baby treated by paediatricians called neonatologists.

The antibodies produced by the woman in the first pregnancy stay in her system for life. If she becomes pregnant again with a rhesus positive baby, these antibodies, which can cross the placenta easily, will enter the baby's bloodstream and attack his or her red blood cells. The baby may survive but will likely have severe anaemia and may develop hearing problems and mental retardation later in life. On the other hand, the baby's red blood cells can be severely destroyed while in the womb, resulting in the baby's death before or shortly after delivery.

To prevent this from happening, women are encouraged to know their blood group and rhesus type. Those with rhesus negative blood group should ensure they receive an injection known as RhoGAM in their first pregnancy, some weeks (between 28 and 32 weeks of pregnancy) before they are due for the delivery of their baby. They should also receive it after delivery, and this should be done for every pregnancy. RhoGAM prevents the woman's immune system from producing those red blood cell-attacking antibodies.

Women with rhesus negative blood should also receive this RhoGAM injection after a miscarriage, voluntary abortion or if they bleed during pregnancy.

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Published Thursday, May 4th 2017

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