Patient education: Pregnancy in Rh-negative people (The Basics)

What does "Rh-negative" mean? — "Rh," or "Rhesus," is the name of a protein that can be found on red blood cells. People who have this protein have an "Rh-positive" blood type. People who do not have this protein have an "Rh-negative" blood type. Having an Rh-positive or Rh-negative blood type does not affect your health. But problems can happen during pregnancy if you have Rh-negative blood and your baby has Rh-positive blood.

Luckily, there is a medicine that can prevent these problems most of the time.

If you have Rh-positive blood, the problems discussed in this article do not apply to you.

How do I know my blood type? — Your doctor will do blood tests at your first prenatal visit. This includes a test to check your blood type.

What problems can happen if I have Rh-negative blood? — Certain problems can happen if you have Rh-negative blood and the baby in your uterus has Rh-positive blood.

Usually, during pregnancy, your blood does not mix with your baby's blood. But sometimes it does, especially right after the baby is born. If a small amount of the baby's blood gets into your blood vessels during delivery, your immune (infection-fighting) system makes proteins called "antibodies." Then, if you get pregnant again in the future, these antibodies can cross the placenta and damage some of the next baby's red blood cells. This can cause a condition called anemia, which is when a person has too few red blood cells. If this happens, the baby can make more red blood cells, but sometimes not enough to prevent anemia.

How do I know my baby's blood type? — Sometimes it's hard to know before the baby is born. If you know your baby's father's blood type, you might know your baby's blood type. If both you and the baby's father have Rh-negative blood, your baby will have Rh-negative blood, too.

If your baby's father has Rh-positive blood, your baby could have Rh-negative or Rh-positive blood. But if you have Rh-negative blood, the doctor or midwife will treat your baby as if they have Rh-positive blood. That way, any possible problems can be prevented.

It is also possible to figure out your baby's Rh blood type before birth by doing a test on your blood. But this test is not done everywhere, and your insurance might not cover it.

What happens next? — If you are Rh-negative, your doctor or midwife will do certain blood tests during pregnancy. These tests check whether you have antibodies in your blood that could cause anemia in your baby.

If you do not have antibodies in your blood and your baby is (or could be) Rh-positive, your doctor or midwife will give you medicine. This medicine prevents your body from making antibodies that could attack your baby's red blood cells. This can prevent anemia or other problems.

The medicine is called anti-D immune globulin (sample brand name: RhoGAM). It usually comes as a shot. You will get it during your third trimester.

After your baby is born, the doctor will do a blood test on the baby to check their blood type. If your baby is Rh-positive, your doctor will give you another dose of anti-D immune globulin soon after delivery. If your baby is Rh-negative, you do not need another dose.

People who are Rh-negative might also get anti-D immune globulin at other times. Doctors give this medicine to Rh-negative people if they:

●Have vaginal bleeding during pregnancy

●Have a test during pregnancy called amniocentesis or chorionic villus sampling (CVS)

●Have a miscarriage, which is when a pregnancy ends on its own before the baby can live outside the uterus

●Have an abortion to end a pregnancy

●Have an ectopic pregnancy, which is a pregnancy that grows somewhere other than in the uterus

What happens if I already have antibodies in my blood? — If you already have antibodies in your blood, anti-D immune globulin will not help. Your doctor will not give you this medicine. But they will do different tests to monitor your baby during pregnancy. If anemia or other problems happen, your doctor will talk with you about possible treatments.

What if I get pregnant again? — If you get pregnant again, you will need treatment again. Rh-negative people are treated with anti-D immune globulin during each pregnancy, as long as they don't have antibodies in their blood.

More on this topic

Patient education: Prenatal care (The Basics)
Patient education: Amniocentesis (The Basics)
Patient education: Chorionic villus sampling (The Basics)
Patient education: Pregnancy loss (The Basics)
Patient education: Bleeding in early pregnancy (The Basics)
Patient education: Abortion (The Basics)
Patient education: Ectopic pregnancy (The Basics)

Patient education: Amniocentesis (Beyond the Basics)
Patient education: Chorionic villus sampling (Beyond the Basics)
Patient education: Miscarriage (Beyond the Basics)
Patient education: Abortion (pregnancy termination) (Beyond the Basics)
Patient education: Ectopic (tubal) pregnancy (Beyond the Basics)