What Do I Need to Know About Rh Factor (Rh) and Anti-D?

Blood typing allows for the classification of your blood into two components:

The first component depends on the presence or absence of two antigens, A and B, resulting in four different blood types: A, B, AB, and O. This information is particularly significant, especially if you may require blood transfusions in the future.

The second component is a protein called the Rh factor (Rh), which can be either positive (+) or negative (-). Approximately 85% of the population is Rh-positive, while the remaining 15% are Rh-negative. In essence, everyone's blood type is a combination of the A, B, or O letters and a plus or minus sign.

Why is it Important to Know if I'm Rh-positive or Rh-negative During Pregnancy?

When Rh-positive blood comes into contact with Rh-negative blood, antibodies may form. This contact can occur during medical procedures such as amniocentesis, chorionic villus sampling, miscarriage, childbirth, and more. This happens when a mother has Rh-negative blood, and the fetus has Rh-positive blood.
During the first pregnancy, the antibodies formed are usually large and do not cross the placenta, so there is no risk to the fetus. However, in subsequent pregnancies, the antibodies produced are smaller and may reach the fetus's bloodstream, potentially causing the mother's antibodies to attack and destroy the fetal red blood cells.

Anti-D Therapy

This condition can be prevented through the administration of a medication called Anti-D. Anti-D (anti-D immunoglobulin) contains antibodies that bind to the red blood cells of the fetus when they enter the mother's bloodstream. In this situation, the mother's body does not recognize that it has encountered Rh-positive blood, and it does not produce antibodies against it.

When Will the Mother Receive Anti-D Injections?

In cases where the mother has Rh-negative blood, she should receive Anti-D injections after certain events or during specific stages of pregnancy. Typically, Anti-D injections are administered before amniocentesis, after a miscarriage, in cases of significant bleeding, at around week 28 of pregnancy, and after childbirth.