Learn about Rh compatibility in pregnancy and how the condition could affect your unborn baby. 

By Dr. Laura Riley
Updated September 25, 2019

During early pregnancy, you'll likely get your blood tested. The results will determine whether you have “Rh factor”— a protein found on the surface of red blood cells. If your blood contains the protein, you’re like the 85% of the U.S. population who is “Rh-positive.” If not, however, you are considered “R-negative,” which might present some complications during pregnancy. Here’s what you need to know about Rh incompatibility.

What is Rh Incompatibility? 

Having Rh-negative blood doesn't pose a problem during pregnancy unless the baby's father is Rh-positive. If that's the case, then there's a chance that your baby could be Rh-positive. Take a mother with Rh-negative blood, add a baby with Rh-positive blood, and you’ve got an incompatibility issue. Your body won't recognize your baby’s Rh factor, and it will produce antibodies to fight them off (this is called sensitization). 

Note that there’s no problem if you and the baby are both Rh positive or Rh negative.

Complications of Rh Incompatibility

During pregnancy, red blood cells from your baby can cross the placenta into your bloodstream. This isn't usually a problem in a first Rh incompatible pregnancy, since the mother won’t produce Rh antibodies fast enough to affect the fetus. However, your body will keep producing these antibodies after you give birth, so there's a chance that your red blood cells will rise up in revolt in your second pregnancy with an Rh-positive baby.

In essence, your body will create an immune response against your own baby because your Rh-negative blood won't tolerate Rh-positive blood cells. (This can also happen after a miscarriage or an abortion with an Rh-positive fetus.) 

If antibodies cross the placenta, they could destroy your baby’s circulating red blood cells, causing severe anemia and jaundice (yellowing of the skin and eyes). In a small percentage of cases, this can result in brain damage, heart failure, or your baby's death.

How to Treat Rh Incompatibility 

If you’re Rh positive with an Rh-negative baby, your practitioner will give you an injection of Rhogam, an Rh-immune globulin, to halt your body's production of antibodies that might attack your baby's blood. This is typically done in the 28th week of your pregnancy, with a follow-up dose within 72 hours after birth. You may also receive a Rhogam shot if you're Rh-negative and experience any bleeding, or if you have a medical procedure during which blood could be transferred, like amniocentesis.

Parents Magazine
Advertisement