blood test tube
profile picture of The Bump Editors
The Bump Editors

What It Means to Be Rh-Negative

If you’ve got Rh-negative blood and baby is Rh-positive, there could be problems. Learn more about the Rh factor and Rh incompatibility.

What is Rh-negative blood?

Everyone’s blood is either Rh-positive or Rh-negative—positive means you have a certain protein (called antigens) on the surface of your red blood cells, and negative means you don’t. If you’re Rh-negative and baby’s RH-positive, then there could be problems.

What are the signs of Rh-negative blood?

There aren’t any symptoms. In fact, your Rh factor doesn’t affect your health at all—except during pregnancy.

Are there any tests for Rh-negative blood?

Yes, a prenatal  blood test will let you and your doctor know whether you’re Rh-negative or Rh-positive. If you’re negative, around week 28 of your pregnancy you’ll get what’s called an indirect Coombs test, which checks to see if your body’s making Rh antibodies, which is a sign baby’s Rh-positive.

How common is Rh-negative blood?  

Only about 15 percent of people are Rh-negative, so it’s not exactly common, but it’s widespread enough that your doctor should know how to handle it.

How did I get Rh-negative blood?

You inherited your Rh negativity. If baby is Rh-positive, he must have inherited his Rh factor from your partner.

How will my Rh-negative blood affect baby?

If baby is Rh-negative too, it won’t. But if baby is Rh-positive, your body could start making antibodies to attack the positive Rh factor in baby’s blood.

This usually isn’t a problem in a first pregnancy—unless you have an abdominal injury, bleeding or your and baby’s blood mixes some other way. But if you have a second baby that’s Rh-positive, those existing antibodies could destroy his red blood cells, causing a condition called hemolytic disease. Hemolytic disease could cause anemia and other problems, and in rare cases, death.
The good news is, as long as you’re seeking prenatal care, your doctor can be on top of an Rh incompatibility and head off problems.

What’s the best way to treat Rh incompatibility?

If your body’s not making Rh antibodies at 28 weeks, you’ll likely get a shot of Rh immunoglobulin (RhIg, aka RhoGAM), which will prevent you from making the antibodies and prevent harm to your next baby (if you have one). You’ll get another RhIg shot within 72 hours of the birth (if baby is Rh-positive) and any time your and baby’s blood may have mixed (which isn’t too likely).

If you are producing Rh antibodies, then RhIg won’t help. Instead, your OB will test your blood regularly to check the antibody levels. If they get high, you might need more tests to check on baby’s health. If baby’s at risk for problems, he might need to be delivered early.

What can I do to prevent Rh incompatibility?

Well, we guess in theory, you and your partner can get blood tests for Rh factor before babymaking—and then not have a baby together if you’re Rh-negative and he’s Rh-positive. But that doesn’t sound very realistic!

What do other pregnant moms do when they’re Rh-negative?

“I’m RH-negative. I’m only 13 weeks right now, so I know I won’t be getting the shot for a while. But I had a previous miscarriage, and I…was given the shot then too.”

“I’ve had the shot with my two previous children and will have it again.”

“I’m also RH-negative, but my doctor did a blood test to find out if the baby was negative as well. Luckily, she is, so I don’t need the shot.”

Are there any other resources for Rh incompatibility?

Expert source: Your Pregnancy and Childbirth: Month to Month by The American College of Obstetricians and Gynecologists.

Plus, more from The Bump: