Rhesus Factor & Pregnancy

Posted Friday, October 14, 2016

Did You Know? Once Rh-sensitized you will always have antibodies

Rh Factor Does Not Affect a Person’s General Health

More than 85% of People are Rh Positive

Most people may not realize there are possible incompatibilities between a mother and her fetus, or realize there can be severe complications because of them. Something as simple as a blood protein can make a difference in their pregnancy.  

Please use this guide as a resource for knowledge and understanding of Rhesus factor, testing, effects on pregnancy and prevention of Rh-sensitized.  

01│What is Rhesus Factor?

Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you're Rh positive. If your blood lacks the protein, you're Rh negative. Rh positive is the most common blood type. Having an Rh negative blood type is not an illness and usually does not affect your health. 


An Rh factor test is a basic blood test. The blood sample is usually taken during the first prenatal visit and sent to a lab for analysis. No special preparation is necessary.  

03 │Effects to Pregnancy

During pregnancy, the woman and fetus do not share blood systems. However, a small amount of blood from the fetus can cross the placenta into the woman’s system. This sometimes may happen during pregnancy, labor, and birth. If you're Rh positive, Rh incompatibility isn't a concern. If you're Rh negative and your baby is Rh positive, your body might produce proteins called Rh antibodies after exposure to the baby's red blood cells. The antibodies produced aren't a problem during the first pregnancy. The concern is with your next pregnancy. If your next baby is Rh positive again, your body will produce Rh antibodies (Rh-sensitized) that can cross the placenta and damage the baby's red blood cells. This could lead to life-threatening anemia, a condition in which there are not enough red blood cells. If this condition is not prevented, each Rh positive baby you carry after your first pregnancy may have severe anemia. 

04 │Rh-Sensitized Prevention

Becoming Rh-sensitized can be avoided with the use of  Rh immune globulin (RhIg) medication if there is a chance of exposure to the   baby's blood. If you're Rh-negative and you've been pregnant before but received this medication a prenatal blood test will help determine if the antibodies that attack Rh-positive blood are present. If the antibodies are present, the medication cannot be administered and there is a risk of complications.   If the antibodies are not present, the medication can be administered to avoid development.  RhIg is given to Rh-negative women in the following situations:

  • At around the 28th week of pregnancy to prevent Rh sensitization for the rest of the pregnancy
  • Within 72 hours after the delivery of an Rh-positive infant
  • After a miscarriage, abortion, or ectopic pregnancy
  • After amniocentesis or chorionic villus sampling

For more information on Rhesus factor and blood, please visit: http://www.bloodjournal.org  

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