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Do I need the Rh Injection?

I am pregnant with my second child, and I had an Rh injection during my last pregnancy. Do I need another one?

Katrena Lacey | Pediatrician

Katrena Lacey

Rh factor refers to a type of protein, or label, on the red blood cells. Most people have the Rh factor, so they are referred to as Rh-positive. However, there are some people without it—they are Rh-negative.

A simple blood test can tell whether you are Rh-positive or Rh-negative.

Rh incompatibility occurs when a pregnant woman has Rh-negative blood and the baby in her womb has Rh-positive blood. The immune system of an Rh-negative mother reacts to the Rh-positive fetal cells that travel through the placenta. Her body creates antibodies against the fetal blood cells. These anti-Rh antibodies may cross back to the developing baby, where they can destroy the baby’s circulating red blood cells.

Rh incompatibility is almost completely preventable. All pregnant women should have a blood test early in their pregnancy to determine their Rh factor status. Pregnant women who are Rh-negative will need a preventative medicine at 28 weeks, and possibly again after birth.


If the father of the infant is Rh-positive or if his blood type cannot be confirmed, the mother is given a mid-term injection of RhoGAM and a second injection within a few days of delivery.

These injections prevent the development of antibodies against Rh-positive blood.

However, women with Rh-negative blood type must continue to receive this injection:

  • During every pregnancy
  • If they have a miscarriage or abortion
  • After prenatal tests such as amniocentesis and chorionic villus biopsy
  • After injury to the abdomen during a pregnancy

If you have further questions or concerns, be sure to discuss them with your health care provider.

A woman who is Rh negative can make Rh antibodies during each pregnancy depending on the Rh status of her baby. Therefore, I recommend seeing your Ob/Gyn early to discuss whether shots are needed.

Learn More
The First Prenatal Visit

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