vials of blood lying on medical forms

Rh factor during pregnancy: why you should know it

Everyone’s blood is positive or negative for the Rh antigen, a protein on the surface of red blood cells. If you already know your blood type, the plus or minus sign after A, B, or O tells you if you have the Rh factor. About 15% of the population is Rh-negative, meaning they do not have the antigen. If you are Rh-negative and the fetus is Rh-positive, which is likely if your partner is Rh-positive, the fetus is at risk of developing Erythroblastosis Fetalis, in which certain antibodies produced by the Rh-negative mother attack the fetus’s red blood cells. You can determine if you are positive or negative for the Rh factor with a routine blood test at your first prenatal healthcare provider's appointment.

If you are Rh-negative

An additional screening test at the beginning of your pregnancy will determine if you have antibodies that attack Rh-positive red blood cells. This can happen if your blood mixes with the fetus’s blood, and your body responds as if it’s allergic to the foreign entity. You will receive a shot of Rh immune globulin as a precautionary measure around 28 weeks to lower your chances of becoming sensitized prior to delivery. If you have not been sensitized to Rh-positive blood, your healthcare provider will perform blood tests 72 hours before delivery to see if you have developed the antibodies. You will also receive a shot of Rhogam at delivery. You should also call your healthcare provider with any bleeding, as you may need a dose of Rhogam at that time as well.

If you develop antibodies to Rh-positive blood

Rh immune globulin is no longer useful, so your fetus will continue to be monitored for conditions like anemia prior to delivery. If the fetus appears to be progressing normally, it can be delivered at full term and receive a blood transfusion. In more severe cases, you might need to deliver prematurely.

Another important consideration is cost. Where you go to get your test or procedure can make a tremendous difference in how much you pay.  It is common for costs to vary as much as 300- 500% for the same procedure depending on where you receive your treatment.  To make sure you’re paying a fair price (the price you should reasonably pay) for your testing, check out Ovia’s price transparency partner Healthcare Bluebook. Their free pricing tool helps patients make smarter and more informed decisions about important medical procedures.

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Read more
  • "The Rh Factor: How It Can Affect Your Pregnancy: FAQ027." ACOG. American College of Obstetricians and Gynecologists, 9/13/2015. Web.
  • "What Is Rh Incompatibility?" National Heart, Lung, and Blood Institute. U.S. Department of Health & Human Services, 1/1/2011. Web.
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