Rh disease

What is Rh factor?

Rh factor is a protein that’s found on some people’s red blood cells. If your red blood cells have the protein, you’re Rh-positive. If your red blood cells don’t have the protein, you’re Rh-negative. Being Rh-positive or Rh-negative doesn’t affect your health. But it can affect your baby during pregnancy if you’re Rh-negative and your baby is Rh-positive.

You can find out if you’re Rh-positive or negative with a blood test. Most people in the United States are Rh-positive. If you’re Rh-negative, your partner can get tested to find out his Rh type.

Rh factor is inherited. This means Rh factor is passed from parents to children through genes. Genes are parts of your body's cells that store instructions for the way your body grows and works.

What is Rh disease?

Rh disease is a dangerous kind of anemia. Anemia is when a person doesn’t have enough healthy red blood cells to carry oxygen to the rest of the body.

Rh disease (also called Rh incompatibility) happens when your blood is Rh-negative and your baby’s blood is Rh-positive. This means your blood and your baby’s blood are incompatible, so it’s not safe for them to mix together. If they do mix, your body makes Rh antibodies that may go from your body through the placenta into your baby’s body, where they attack and destroy her red blood cells. The placenta grows in your uterus (womb) and supplies your baby with food and oxygen through the umbilical cord.

Even though you and your baby don’t share blood, a small amount of your baby’s blood can mix with yours during pregnancy. This can happen if:

• Your baby’s blood crosses into your blood through the placenta.
• You have an amniocentesis (also called amnio) or chorionic villus sampling (also called CVS). These are prenatal tests that your health care provider may recommend during pregnancy.
• You have bleeding during pregnancy.
• Your baby’s in a breech position (feet-down instead of head-down) before labor and your provider tries to rotate (move) him around so he’s head-down.
• You get hit in the belly during pregnancy.
• You have a miscarriage or an ectopic pregnancy. A miscarriage is when a baby dies in the womb before 20 weeks of pregnancy. An ectopic pregnancy is when a fertilized egg implants itself outside of the uterus (womb) and begins to grow.

If you have Rh antibodies, you’re called Rh-sensitized.

Is your baby at risk for Rh disease?

Your baby is at risk for Rh disease only if you’re Rh-negative and your baby is Rh-positive. Your baby is Rh-positive depending on the blood of you and your baby’s father. Here’s how it works:

• If both you and your baby’s father are Rh-positive: Your baby’s blood is Rh-positive, and there’s no risk of Rh disease in your baby.
• If both you and your baby’s father are Rh-negative: Your baby’s blood is Rh-negative, and there’s no risk of Rh disease for your baby.
• If you’re Rh negative and your baby’s father is Rh-positive: Your baby’s blood may be Rh-positive. Your baby is at risk for Rh disease and needs to be checked closely.

Talk to your provider about having your blood and your baby’s father’s blood tested to find out if your baby may be at risk.

If it’s your first pregnancy, your body usually doesn’t make enough Rh antibodies to harm your baby. But if you get pregnant again, your body produces more antibodies that can cause Rh disease in your baby.

Who gets tested for Rh factor?

You, your partner and your baby can have tests to find out if you’re Rh-positive or negative and if your baby is at risk for Rh disease. You get a blood test at your first prenatal care visit to find out if you’re Rh-positive or Rh-negative. If you’re Rh-positive, there’s no risk of Rh disease in your baby. If you’re Rh-negative:

• You get a test called an antibody screen to see if you have Rh antibodies in your blood.
• If you don’t have Rh antibodies, your partner gets tested to see if he’s Rh-positive or negative.
• If your partner is Rh positive or you don’t know your partner’s Rh factor, your provider may recommend an amniocentesis to check your baby’s Rh factor or his bilirubin level. Bilirubin is a yellow substance that can build up in your baby’s blood when his liver isn’t working right. You get a second antibody test at 28 weeks of pregnancy. If this second test shows that your baby has anemia, your provider may do a Doppler ultrasound to check the flow of blood into your baby’s head.

Can Rh disease cause problems for your baby?

Rh disease can cause serious problems for your baby, including:

• Anemia
• Brain damage
• Heart failure
• Jaundice. Jaundice can make your baby’s eyes and skin look yellow. A baby has jaundice when his liver isn't fully developed or isn’t working. If jaundice is severe and isn’t treated, a baby can develop a kind of brain damage called kernicterus.
• Stillbirth. Stillbirth is when a baby dies in the womb after 20 weeks of pregnancy.
• Death after birth

If you’re Rh-negative, can you protect your baby from Rh disease? 

Rh disease can be prevented in your baby if you get treatment at the right times. If you haven’t developed Rh antibodies, your provider can give you a shot of Rh immunoglobulin called Rho(D) immune globulin (brand name RhoGAM®). RhoGAM can prevent your body from producing Rh antibodies so your baby and future pregnancies won’t get Rh disease. RhoGAM doesn’t work if your body has already started making Rh antibodies in a previous pregnancy. This is why it’s really important to get prenatal care as early as possible in every pregnancy.

If you’re RH-negative, you get RhoGAM:

• At about 28 weeks of pregnancy
• Within 72 hours after the birth if your baby is Rh-positive or if his Rh is unknown
• After any situation in which your blood and your baby’s blood may mix, like amnio or CVS, miscarriage, ectopic pregnancy or a hit to your belly.

Your provider watches your baby closely during pregnancy to check his health and for signs of anemia. In your third trimester, your provider may use amnio or a special ultrasound called Doppler to check your baby. Ultrasound is a prenatal test that uses sound waves and a computer screen to show a picture of your baby inside the womb. A Doppler ultrasound helps a provider check your baby’s heartbeat and measure the blood flow in the umbilical cord and certain blood vessels.

If your baby has Rh disease, how is she treated?

If your baby has Rh disease, she can be treated to help prevent serious health problems.

If your baby has mild Rh disease, you may be able to have a full-term pregnancy. Full term means your baby is born between 39 weeks and 40 weeks, 6 days. After birth, your baby may need certain medicine, and she may need treatment for jaundice. Sometimes Rh disease is so mild that your baby doesn’t need any treatment. Most babies recover fully from mild Rh disease.

If your baby develops severe Rh disease and severe anemia before birth, you may have to give birth early, before her due date. She may need a blood transfusion with new blood to replace red blood cells that the Rh antibodies destroyed. Babies can get a blood transfusion in the womb as early as 18 weeks of pregnancy; they also can get a transfusion after birth.

If your baby is born with severe jaundice, she needs quick treatment to prevent more serious complications.

Last reviewed: July, 2017