Understanding Rh factor and its importance in pregnancy

Ever wondered what it means to have a positive or a negative sign in front of your blood group? Why is an O positive different from an O negative blood group? Why is it so important to not only match the blood group but also the positive or negative factor?

The answer lies in understanding all about the Rh factor. The Rh factor or Rhesus factor is a certain type of protein that is found on the surface of red blood cells. This protein is present on the red blood cells of approximately 85% individuals – making them Rh-positive, while those who do not have the protein present on their blood cells are known to be Rh- negative.

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In most cases, the Rhesus factor is not associated with any major health risks. However, during pregnancy and childbirth, it becomes crucial to take precautions for the same, especially if the mother is Rh negative. When a Rh-negative mother carries a Rh-positive fetus, it is termed as an Rh incompatibility. 

Generally mixing between the blood or the blood cells of the mother and unborn baby is less common, but in some situations this blood exchange of small amounts from the fetus to the maternal bloodstream may occur. These scenarios include: Amniocentesis, trauma to the abdomen during pregnancy, bleeding during pregnancy, and labor & birth. 

If at any point the red blood cells from the Rh-positive unborn baby were to cross into the Rh-negative mother’s bloodstream through the placenta, the mother’s immune system would detect the Rh-positive fetal cells as foreign substances and produce antibodies against these positive cells.

Further, if these antibodies were to cross back through the placenta from the Rh-negative mother’s body to the Rh-positive unborn baby, these antibodies would then begin attacking the baby’s red blood cells. Red blood cells are known to carry oxygen, so damage to the baby’s red blood cells can cause a lack of oxygen to the unborn baby, anemia, and in serious complications, even brain damage.

Research backs that most first-borns are not affected by this crossing over as it takes time for the mother’s body to create the antibodies (unless there is a history of a miscarriage or an abortion. It is normally the consecutive pregnancies that are at a higher risk of complications.

However, modern antenatal care and screening now have ways to avoid these complications. Mothers are screened for the Rh factor as part of their initial prenatal screening. If a mother is found to be Rh negative, she is simply given an injection for Rh immunoglobulins that would prevent her body from creating antibodies to Rh positive blood during pregnancy. 

Dr. Vanshika Gupta Adukia is a pregnancy/childbirth and lactation specialist, a pelvic floor physiotherapist and founder of Therhappy, Mumbai.

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