What Is RhoGAM?

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RhoGAM is a shot given to pregnant people whose blood is negative for Rhesus factor (Rh) protein but who are carrying an Rh-positive fetus.

This incompatibility can cause a pregnant person's immune system react to the Rh protein on the fetus's red blood cells that have entered their bloodstream. This potentially causes complications like fetal brain damage and pregnancy loss in future pregnancies. RhoGAM almost completely prevents this.

RhoGAM contains Rho(D) immune globulin, which are antibodies specific to the Rh protein. These antibodies coat the Rh protein on any fetal blood cells that have entered the pregnant person's bloodstream. This and other mechanisms prevent the pregnant person's immune system from reacting to fetal Rh protein and developing their own antibodies, which could endanger a future pregnancy.

This shot is not only safe for both pregnant people and their fetuses, but it can save a future baby's life.

Read on to learn more about exactly why the RhoGAM shot is so important in cases of Rh incompatibility, when it's given, and potential side effects.

Doctor holding medication in the syringe, preparing for injection for a pregnant woman during a medical procedure in the clinic, close-up view

RossHelen / Getty Images

Importance of RhoGAM

If a person who is Rh-negative is pregnant with an Rh-positive fetus, there is a risk that if the parent's blood comes into contact with the fetus's blood, the parent could develop antibodies that attack Rh-positive red blood cells.

These antibodies could cause harm to an Rh-positive fetus, such as:

  • Fetal anemia (low iron in the blood due to hemolysis)
  • Miscarriage
  • Stillbirth
  • Serious illness
  • Jaundice (from high bilirubin due to hemolysis)
  • Brain damage (also due to high bilirubin)
  • Fluid build-up, known as hydrops fetalis
  • Problems with hearing, movement, and mental function
  • Seizures

Because it takes time to develop antibodies, these effects are not usually seen in the first Rh-positive pregnancy, but may cause harm to any Rh-positive fetuses in the future.

Once these antibodies are made (called sensitization), they are permanent, but it is possible to prevent them from developing by administering an injection of RhoGAM before the antibodies develop. RhoGAM is a sterilized solution made from human blood that contains Rho(D) immune globulin.

The pregnant parent should have their blood type, including Rh factor, tested and antibody screening done if indicated as part of early prenatal care. The fetus's blood type is not routinely tested.

Rh factor is inherited in an autosomal dominant pattern, meaning it will be expressed whether a person has one or two copies of the gene, and there is no difference in expression in people of any sex. If both genetic parents are Rh-negative, their children will be, too.

If the sperm-contributing parent is Rh-positive and the egg-contributing parent is Rh-negative, there is a risk that their children will be Rh-positive.

If the pregnant parent is Rh-negative and their antibody screen is negative, a RhoGAM shot will be given if the other genetic parent is Rh-positive or if their Rh-factor is unknown. In cases where an Rh-negative pregnant person is not a genetic parent of the fetus, they will be given RhoGAM if either genetic parent is Rh-positive or their Rh-factors are unknown.

Is RhoGAM Safe for My Baby?

RhoGAM is considered safe to give to pregnant people. Millions of doses have been given to Rh-negative people who are or were pregnant and have never been shown to harm the fetus.

When Is RhoGAM Given?

The chance of parent and fetal blood mixing is highest at birth. But it can happen during the third trimester because of the growing placenta and thinning of the membranes that separate the parent's blood and the fetus's blood.

RhoGAM is given at around the 28th week of pregnancy. It is effective for about 13 weeks.

Shortly after birth, the baby will have a blood test to determine Rh type. If the baby is Rh-positive, the parent who gave birth will receive another RhoGAM shot within 72 hours from the time of birth. If the baby is Rh-negative, no second shot is needed, as there is no chance of sensitization.

A RhoGAM shot should also be administered to an Rh-negative person within 72 hours after:

How Do I Know If My Baby Is Rh-Positive?

The fetus's Rh type is usually not tested during pregnancy, as it can only be done using invasive procedures. If the pregnant parent is Rh-negative, the RhoGAM shot will be given during pregnancy if there is a possibility that the fetus is Rh-positive, without needing a confirmation.

After birth, a blood test will be done on the baby to determine their Rh type and to see if another RhoGAM shot is needed.

Common Side Effects of RhoGAM

The most common side effects of RhoGAM are:

  • Swelling, hardening, redness, and/or mild pain at the site of injection
  • Slight fever (less common)

Allergic Reactions to RhoGAM

Allergic reactions to RhoGAM are rare.

Signs or symptoms of an allergic reaction include:

  • Itchy rash
  • Tightness of the chest
  • Wheezing
  • Low blood pressure
  • Anaphylaxis (which may include swelling of the throat or tongue, shortness of breath, vomiting, lightheadedness, and/or hives)

Wait at least 20 minutes to leave after receiving RhoGAM so you can be observed for a potential reaction.

RhoGAM Safety

RhoGAM has been used since the 1960s and is considered very safe.

Because it is made from human blood, there is an extremely remote possibility of contracting a blood-borne infection. The measures taken to prevent this, including testing, makes this risk incredibly small. No one in the United States has gotten an infection from using RhoGAM since 1985.

The chances of developing Rh sensitization, and the risks to pregnancies that come with it, are much higher than the risk of potential problems from the RhoGAM injection.

RhoGAM and Vaccines

Some vaccines (ones that contain live viruses) could be less effective when taken within three months of getting a RhoGAM shot. However, there is no evidence RhoGAM reduces the effectiveness of rubella vaccination after delivery, so this vaccine is still given when needed.

Other vaccines are fine to take with RhoGAM. If you have had or will need a RhoGAM shot, talk to your healthcare provider about the timing of vaccines, including if you are planning on traveling out of the country.

Who Should Not Get a RhoGAM Shot?

People who should not get a RhoGAM shot include:

  • Babies (RhoGAM is given only to the parent who gives birth, never to the baby or fetus)
  • Those who are Rh-positive
  • People who have hemolytic anemia
  • Those who have had an allergic reaction to human immune globulin
  • People who already have Rh sensitization (have already developed antibodies)


Complications can arise for future (and rarely, current) pregnancies if an Rh-negative person is pregnant with an Rh-positive fetus. A RhoGAM shot is administered to the Rh-negative person around the 28th week of pregnancy. A second RhoGAM shot is given after birth if the baby is determined to be Rh-positive.

A RhoGAM shot should also be administered after any time an Rh-negative pregnant person may have come into contact with Rh-positive blood, such as with pregnancy loss, pregnancy termination, injury to the abdomen during pregnancy, or some forms of prenatal testing.

Complications and serious side effects from RhoGAM are rare, and the risks to future pregnancies from not getting the shot are greater than the risks of getting the shot.

Frequently Asked Questions

  • What is Rh incompatibility in pregnancy?

    If a pregnant person is Rh-negative and their fetus is Rh-positive, the pregnant parent can be exposed to the fetus's Rh-positive blood, causing antibodies to develop. These antibodies can then attack the fetus's Rh-positive red blood cells. Future pregnancies are also at risk if antibodies develop.

  • How does a RhoGAM shot work?

    RhoGAM is a medication that contains antibodies against Rh factor protein. It stops the body from making its own antibodies against Rh-positive blood if a pregnant parent is Rh-negative and is exposed to the blood of their Rh-positive fetus.

  • Is RhoGAM needed for every pregnancy?

    Unless they have already been determined to be sensitized (have created antibodies), a RhoGAM shot is needed any time an Rh-negative person is pregnant with a baby that is (or could be) Rh-positive, even if the person has received RhoGAM for previous pregnancies.

    RhoGAM should also be given after any potential mixing of an Rh-negative pregnant parent's blood and fetal blood, including after a miscarriage, pregnancy termination, some prenatal tests, or an injury to the abdomen during pregnancy.

  • When is RhoGAM given during pregnancy?

    RhoGAM is given around week 28 of pregnancy. Another shot of RhoGAM is given shortly after birth if the baby is Rh-positive.

  • Is Rh factor the same as blood type?

    When blood is typed, it is tested for both ABO and Rh types. These are two different blood type systems, which are inherited separately. A blood type is typically stated with its ABO type and its Rh type, such as A+, B-, O+, AB-, etc.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mount Sinai. Rh incompatibility.

  2. Kedrion Biopharma Inc. RhoGAM FAQs.

  3. MedlinePlus. Rh incompatibility.

  4. Children's Hospital of Philadelphia. Blood types in pregnancy.

  5. American College of Obstetricians and Gynecologists. The Rh factor: how it can affect your pregnancy.

  6. American College of Nurse-Midwives. Rh-negative blood type in pregnancy. Journal of Midwifery & Women’s Health. 2020;65(1):185-186. doi:10.1111/jmwh.13086

  7. Centers for Disease Control and Prevention. General best practice guidance for immunization.

By Heather Jones
Heather M. Jones is a freelance writer with a strong focus on health, parenting, disability, and feminism.