What Is RhoGAM?

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In addition to the four major blood groups, there is a component of blood called the Rhesus factor (Rh), which is protein found on the surface of the blood in some people. People who have this protein are called Rh-positive, and people who don't are called Rh-negative.

If a person who is Rh-negative is pregnant with a fetus that is Rh-positive, this could cause problems with that or future pregnancies. RhoGAM is an injection given to the pregnant parent to prevent these problems from occurring.

Read on to learn more about RhoGAM and why it's important.

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 a fetus who is Rh-positive, 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)
  • Miscarriage
  • Stillbirth
  • Serious illness
  • Jaundice (from high bilirubin)

Because it takes time to develop antibodies, these effects are not usually seen in the first 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 a very small amount of Rh-positive proteins.

The pregnant parent often has their blood type, including Rh-factor, tested as part of early prenatal care. The fetus's blood type is not routinely tested.

Because Rh-factor is inherited, if both genetic parents are Rh-positive, their baby will be Rh-positive. If both genetic parents are Rh-negative, their baby will be too. If one genetic parent is positive and one is negative, their baby could be either.

RhoGAM is needed only if the pregnant parent is Rh-negative and there is a chance the fetus is Rh-positive (called Rh incompatibility). If the pregnant parent is Rh-positive, nothing else needs to be done. If the pregnant parent is Rh-negative, a RhoGAM shot will be given if the other genetic parent is Rh-positive or if their Rh-factor is unknown.

Is RhoGAM Safe for My Baby?

RhoGAM is considered safe to give to pregnant parents. Millions of doses have been given to Rh-negative parents who are or were pregnant and has 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 blood type and 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 that cause fever or shortness of breath are rare, but can occur after receiving RhoGAM. Small reactions are more common, such as redness or swelling at the injection site.

Other 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 a small amount of 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. Other vaccines are fine to take with RhoGAM. If you have had or will need a RhoGAM shot, talk to your healthcare provider about 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 parent is pregnant with an Rh-positive fetus. A RhoGAM shot is administered to the Rh-negative parent around the 28th week of pregnancy. A second RhoGAMshot 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 parent may have come into contact with Rh-positive blood, such as with a miscarriage or abortion, 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.

A Word From Verywell

If you are pregnant, ask your healthcare provider to test your blood for Rh-factor. If you are Rh-negative and your baby's other genetic parent is Rh-positive (or you aren't sure), don't worry. The RhoGAM shot is a safe and effective way to prevent problems that could arise from Rh-incompatibility.

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 RhoGAM work?

    RhoGAM is a medication that contains a very small amount of Rh-positive blood. It stops the body from making 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), RhoGAM 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, abortion, 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.

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

  5. Kedrion Biopharma Inc. RhoGAM faqs.