Rh Incompatibility During Pregnancy

Rh Incompatibility is blood disorder found in pregnancy that can affect both the mother and baby. It occurs when the mom-to-be is Rh-negative blood and her fetus she is carrying has Rh-positive blood. The Rh-positive or Rh-negative characteristics refer to the Rh factor which is a protein in red blood cells.

The presence of Rh factor means that you are Rh-positive. If you do not have this Rh factor than you are said to be Rh-negative. This Rh factor is an inherited trait that is passed on down from biological parents to the child.

The majority of people are Rh-positive. The Rh factor does not have an affect on your general health, but it does cause problems in pregnancy if there is an Rh incompatibility.

Cross Blood Reaction

Did you know that blood from your baby’s body could cross over the placenta into the bloodstream of the mom? When the mom is Rh-negative and the baby is Rh-positive, the mom’s body will react to the foreign material in the baby’s blood and see it as a foreign substance.

The mom’s body will create antibodies (proteins) that will attack the baby’s Rh-positive blood during the pregnancy. Normally this is not a problem in a first pregnancy because the baby is usually born before the antibodies can be formed but in later pregnancies if the baby is Rh-positive the Rh antibodies can cross over the placenta and attack the baby’s red blood cells causing hemolytic anemia in the baby.

The baby’s body will not have the oxygen-rich blood it needs and this can lead to severe problems and can even be fatal to the baby.


Rh Incompatibility is one of the things routinely checked in prenatal visits so as long as the woman is getting early and regular prenatal care including Rh factor screening the problem will be discovered in time to do something about it. If Rh Incompatibility is present, your doctor will monitor you more carefully throughout the pregnancy and prescribe treatment if it becomes necessary to do so.

If a woman is Rh-negative she will need to take injections of a medicine called Rh immune globulin every time she has a baby with Rh-positive blood. If a woman has a miscarriage, or a blood transfusion she can also contract a problem with Rh incompatibility.

If Rh incompatibility is not caught due to substandard or lack of prenatal care the newborn can show signs of hemolytic anemia, which may be mild or severe such as jaundice, and a buildup of fluid. If the bilirubin (which causes the jaundice) is too high for too long it can lead to brain damage in the newborn.

The build up of fluid detected in a newborn with Rh incompatibility is caused by heart failure. This build up of fluid in a newborn due to heart failure is called, “hydrops fetalis”. If the baby has severe hemolytic anemia it can be fatal at the time of birth or shortly after birth.