Did My Miscarriage Happen Because I'm Rh Negative?

Having an Rh-negative blood type requires special attention during each pregnancy. In the past, Rh-negative women were often at risk for miscarriage in the second or third trimester. This now happens rarely as pregnant Rh-negative women are routinely given the RhoGAM injection to lessen this risk. 

Learn how your Rh blood type can affect your chances of pregnancy loss and the health of future pregnancies.

What Is Rh Factor?

Just as people have major blood types (A, B, AB, or O), they also have an Rh factor blood type, which is usually noted as Rh-positive or Rh-negative. Rh stands for rhesus and refers to a protein often found on red blood cells.

More than 85% of people are positive for the Rh(D) protein, which is known as being Rh-positive. Some people lack the Rh(D) protein and they are referred to as Rh-negative. This does not affect their general health in any way.

Genetics determines who is Rh-positive and who is Rh-negative. If both parents are Rh-negative, their offspring will be as well. But if the mother is Rh-negative and the father is Rh-positive, the child may be either Rh-positive or Rh-negative.

Preventing Sensitization to Rh Factor

Sensitization to Rh factor can be thought of as developing a reaction to your baby's blood. If you are Rh-negative and you are exposed to Rh-positive blood, you can produce antibodies to Rh(D).

Blood cells from an Rh-positive fetus can enter your bloodstream during pregnancy and trigger the development of these antibodies. This can happen late in pregnancy or during delivery and also may happen if you have a miscarriage, abortion, or ectopic pregnancy.

If this is your first Rh-positive pregnancy, that fetus is usually not affected as it takes time for the antibodies to develop. In your future pregnancies, these antibodies can pass through the placenta and attack Rh-positive red blood cells ​in the developing fetus. This can lead to hemolytic disease of the newborn or to pregnancy loss.

In order to prevent the formation of these antibodies, you may get an injection of RhoGAM (Rh immunoglobulin or RhIg). This injection contains antibodies that will attach to any Rh-positive cells. This prevents you from developing your own antibodies that can cause problems in future pregnancies or transfusions.

If you are Rh-negative, you will be given this injection at the 28th week of pregnancy and again just after delivery if your baby is Rh-positive. If you have a miscarriage, trauma, or induced abortion, you will be given this shot within three days of the exposure. You will also be given this shot after invasive procedures such as amniocentesis, chorionic villus sampling, or fetal surgery.

Rh-Negative Mother and Second Pregnancy

You will be tested to see if you have developed the Rh(D) antibody. If you lack the antibody, the pregnancy should not have any complications due to Rh factor. You will be given RhoGAM at the appropriate times to prevent sensitization.

It is important to note that Rh antibodies are typically harmless until the second or later pregnancies. In these situations, if you have been sensitized, a pregnancy with an Rh-positive fetus can have complications and will be closely monitored. There is an increased risk of stillbirth due to a condition called immune hydrops fetalis that can develop in the second and third trimesters. This condition is not a factor in first-trimester miscarriages, which are usually due to chromosomal abnormalities in the baby.

It is important to note that being Rh-negative in and of itself does not cause miscarriage or pregnancy loss. You are only at risk if you have been sensitized. The risk is very small if you have the recommended RhoGAM shots during pregnancy, or after an ectopic pregnancy, pregnancy loss, or induced abortion.

Pregnancy When Sensitized to Rh Factor

Even if you have lost a pregnancy due to Rh incompatibility or you are sensitized to Rh factor, you can have successful pregnancies in the future. If your partner is Rh-negative, your baby also will be and is at no risk from Rh antibodies. If your partner is Rh-positive, there is a strong chance that your baby will be too, and the pregnancy will have risks for miscarriage or hemolytic anemia of the newborn.

You should be vigilant about prenatal care. Your doctor will check the fetus throughout your pregnancy for any signs of anemia. If severe anemia is seen, your doctor may recommend an early delivery or a fetal blood transfusion while the baby is still in your uterus. After delivery, your baby may be given a blood transfusion.

A Word From Verywell

Having a miscarriage causes emotional and physical trauma. Talk to your doctor about your concerns over your Rh status as well as any other factors that could have led to your pregnancy loss. If you decide to become pregnant again, be assured that many women who are Rh-negative have gone on to have full-term pregnancies and healthy children.

Also, read about ABO blood type incompatibility between a mother and her baby.