Rh Factor in Pregnancy

During pregnancy it is necessary to do a blood draw to find out your blood type. There are two components to this testing, a major blood group (A, B, AB, and O) and an Rh factor (positive or negative).

What is Rh Factor?

Rh factor is a protein that is found on your red blood cells. Most of the population has the Rh factor present on their red blood cells. This group of people are considered to be Rh positive. The rest of the population does not have the Rh factor present on their cells, these people are Rh negative.

What Are the Health Issues for Rh Negative Pregnant Women?

During pregnancy you do not share blood systems with your baby. However, your baby's blood can cross the placenta into your blood.

The Rh factor becomes a problem when an Rh negative person's blood comes into contact with an Rh positive person's blood. If this contact occurs, the person with Rh negative blood develops antibodies to fight the Rh factor. In this instance the antibodies see the Rh factor as a harmful substance, or a foreign substance that does not belong in the blood. This is called Rh sensitization. When sensitization occurs these antibodies can go and attack the baby's blood. This can cause a serious health condition in the baby called hemolytic disease. Rh sensitization can also affect future pregnancies.

An Rh negative woman's blood can become sensitized if she is pregnant with an Rh positive fetus. Other ways an Rh negative woman's blood can become sensitized are with a miscarriage, an induced abortion, an ectopic pregnancy, or a blood transfusion.

How Can You be Screened for Rh Sensitization?

A simple blood test, a red blood cell antibody screen, can be drawn and sent to the laboratory to check for antibodies against the Rh factor.

How can Rh Sensitization be Prevented?

If your body has not made antibodies against the Rh factor, hemolytic disease can be prevented. Rh immunoglobulin (RhIg), or Rhogam, is a human blood product (made from human blood plasma) that can prevent sensitization of an Rh negative woman. In a normal pregnancy, when the woman is Rh negative, the Rhogam is given by intramuscular injection at 28 weeks gestation and again after you deliver your baby. Rhogam is safe for use in pregnancy and has been used since the late 1960's.

What do I do if I'm Rh Sensitized?

Every situation is unique and requires individualized treatment. Your health care provider will work closely with you throughout the pregnancy to plan the safest course of treatment for your baby.

If you have any questions regarding your Rh status please speak to your provider at your next appointment.