Rh Mismatch: What Does It Mean To You And Your Baby?

Rh factor is simply a variation in the blood composition, just like the differences in people’s blood groups. Red blood cells have a protein on their surface, called Rh, which, if present, is called Rh positive or negative in case it is absent. Rh factor is predominantly a play of the genes, meaning that is passed down from a parent to her child. Depending on the Rh factor of the father and the mother, the fetus can be either RH positive or negative.

In 85% of cases the Rh factor is positive. But Rh negative does exist. So what happens if you are Rh negative and the fetus inside you is Rh positive?

In This Article

1. How does the RH factor affect pregnancy?

The problems arise if the mother is Rh negative and the baby’s positive. Even in this case, the fetus will not have a problem if it is the woman’s first pregnancy.

The conflicting Rh factors give rise to a situation called Rh incompatibility. During pregnancy, if an Rh negative mother’s blood comes in contact with her Rh positive baby, the mother’s body starts making antibodies, which attack the Rh factor considering it an enemy. This reaction of the immune system is called Rh sensitization.

2. Why does the mother’s blood come in contact with her fetus?

Although the mother and the baby do not share blood systems, some amount of blood can cross from the fetus to the mother through the placenta. This can occur during labor, birth, bleeding during pregnancy, manual rotation of the baby, blunt trauma to the abdomen and more such situations.

3. What are the implications of Rh incompatibility between mother and the fetus?

As the mother’s body does not create many antibodies by the time the baby is born, in most cases of first pregnancy, there are hardly any problems with the baby. However, if proper preventive treatment is not given to the mother at this stage, there can be issues with the second pregnancy, putting the baby at a risk of RH disease.

4. The effect of blood contact on the fetus during pregnancy

When the antibodies created by an Rh negative mother cross the placenta and attack the blood of the Rh positive fetus, some of the fetal red blood cells can be destroyed in the process. This situation can cause hemolytic anemia, which is the medical term for the process where red blood cells are destroyed at a rate faster than what the body can replenish. As the red blood cells are responsible for carrying oxygen to various parts of the body, the fetus does not get enough oxygen in this state, causing serious illness.

5. Is it possible to develop antibodies even if the pregnancy is not carried to term?

There are cases when proper preventive treatment is not given after a miscarriage, ectopic pregnancy, and induced abortion. In such a case, if an Rh negative mother conceives after facing one of these situations, the Rh positive fetus is at a risk of getting Rh-related complications such as anemia, brain damage, heart failure, jaundice, and stillbirth.

6. How can you know if you have RH incompatibility?

A simple blood test, which is called an antibody screen, can reveal if the body is creating antibodies and how many of them have been created. This test is usually carried out twice during the interim of pregnancy.

7. Is it possible to prevent this situation altogether?

If a mother is Rh negative, a doctor will usually suggest giving you a shot of Rh immunoglobulin (RhIg). This is usually developed from donated blood and when given to a mother, it prevents the creation of antibodies. However, it is not effective in case a mother is already RH sensitized. It can be given and prescribed by the doctor at different stages of pregnancy.

It is highly advisable and necessary for proper screening and testing during pregnancy, to ensure that there is no RH incompatibility between the mother and the fetus. However, in case there is an issue, necessary precaution can always be taken at the right time to restrict the situation.

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